[Federal Register: September 24, 2002 (Volume 67, Number 185)]
[Proposed Rules]               
[Page 59883-59932]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr24se02-25]                         
 

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Part II





Department of the Interior





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Fish and Wildlife Service



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50 CFR Part 17



Endangered and Threatened Wildlife and Plants; Critical Habitat 
Designation for Four Vernal Pool Crustaceans and Eleven Vernal Pool 
Plants in California and Southern Oregon; Proposed Rule


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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

RIN 1018-AI26

 
Endangered and Threatened Wildlife and Plants; Critical Habitat 
Designation for Four Vernal Pool Crustaceans and Eleven Vernal Pool 
Plants in California and Southern Oregon

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Proposed rule.

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SUMMARY: We, the Fish and Wildlife Service (Service), propose 
designation of critical habitat for 4 vernal pool crustaceans and 11 
vernal pool plants with a total area being proposed of approximately 
672,920 hectares (ha) (1,662,762 acres (ac)). The proposed designation 
of critical habitat is for Conservancy fairy shrimp (Branchinecta 
conservatio) 165,820 ha (409,735 ac), longhorn fairy shrimp 
(Branchinecta longiantenna) 40,605 ha (100,333 ac), vernal pool fairy 
shrimp (Branchinecta lynchi) 457,556 ha (1,130,605 ac), and vernal pool 
tadpole shrimp (Lepidurus packardi) 291,370 ha (719,965 ac) 
(collectively referred to as ``vernal pool crustaceans'' in the 
remainder of this document), and Butte County meadowfoam (Limnanthes 
floccosa ssp. californica) 16,320 ha (40,326 ac), Contra Costa 
goldfields (Lasthenia conjugens) 14,499 ha (38,297 ac), Hoover's spurge 
(Chamaesyce hooveri) 81,744 ha (201,987 ac), succulent (or fleshy) 
owl's-clover (Castilleja campestris ssp. succulenta) 125,217 ha 
(309,407 ac), Colusa grass (Neostapfia colusana) 132,608 ha (327,670 
ac), Greene's tuctoria (Tuctoria greenei) 142,984 ha (353,308 ac), 
hairy Orcutt grass (Orcuttia pilosa) 65,671 ha (162,272 ac), Sacramento 
Orcutt grass (Orcuttia viscida) 24,632 ha (60,865 ac), San Joaquin 
Valley Orcutt grass (Orcuttia inaequalis) 101,059 ha (249,714 ac), 
slender Orcutt grass (Orcuttia tenuis) 71,035 ha (175,524 ac), and 
Solano grass (Tuctoria mucronata) 7,345 ha (18,149 ac) (collectively 
referred to as ``vernal pool plants'' in the remainder of this 
document), pursuant to the Endangered Species Act of 1973, as amended 
(Act). Because many of the units proposed for different species 
overlap, the total critical habitat area we are proposing is much less 
than the sum of the areas for each species. The proposed units are in 
39 counties in California and one county in southern Oregon.
    If this proposed rule is made final, section 7 of the Act would 
prohibit destruction or adverse modification of critical habitat by any 
activity funded, authorized, or carried out by any Federal agency. 
Section 4 of the Act requires us to consider economic and other impacts 
of specifying any particular area as critical habitat.
    We solicit data and comments from the public on all aspects of this 
proposal, including data on the economic and other impacts of the 
designation. We may revise or further refine critical habitat 
boundaries prior to final designation based on habitat and additional 
plant and animal surveys, public comments on the proposed critical 
habitat rule, the completion and approval of Habitat Conservation Plans 
(HCPs), and new scientific and commercial information, and data 
concerning potential economic impacts from the proposed designation.

DATES: We will accept comments from all interested parties until 
November 25, 2002. Public hearing requests must be received by November 
8, 2002.

ADDRESSES: If you wish to comment, you may submit your comments and 
materials concerning this proposal by any one of several methods.
    1. You may mail written comments and information to the Field 
Supervisor, Sacramento Fish and Wildlife Office, U.S. Fish and Wildlife 
Service, 2800 Cottage Way, Room W-2605, Sacramento, CA 95825.
    2. You may hand deliver written comments to our Sacramento Fish and 
Wildlife Office at the address given above.
    3. You may send comments by electronic mail (e-mail) to fw1--
vernalpool@fws.gov. See the Public Comments Solicited section below for 
file format and other information about electronic filing.
    Comments and materials received, as well as supporting 
documentation used in the preparation of this proposed rule, will be 
available for public inspection, by appointment, during normal business 
hours at the above address.

FOR FURTHER INFORMATION CONTACT: Arnold Roessler or Susan Moore, at the 
Sacramento Fish and Wildlife Office address above (telephone 916/414-
6600; facsimile 916/414-6710). Information regarding this proposal is 
available in alternate formats upon request.

SUPPLEMENTARY INFORMATION:

Background

    The vernal pool crustaceans and plants addressed in this proposed 
rule live in vernal pools (shallow depressions that hold water 
seasonally), swales (shallow drainages that carry water seasonally), 
and ephemeral freshwater habitats. None are known to occur in riverine 
waters, marine waters, or other permanent bodies of water. The vernal 
pool habitats of the four vernal pool crustaceans and eleven plants 
addressed in this proposed rule have a discontinuous distribution west 
of the Sierra Nevada that extends from southern Oregon through 
California into northern Baja California, Mexico (Holland and Jain 
1978, 1988, Eriksen and Belk 1999).
    Vernal pools are a unique kind of wetland ecosystem. Central to 
their distinctive ecology is the fact that they are vernal or 
ephemeral, occurring temporarily--typically during the spring--and then 
disappearing until the next year. They are wet long enough to be 
different in character and species composition from the surrounding 
upland habitats, and yet their prolonged annual dry phase prevents the 
establishment of species typical of more permanent wetlands. In 
California, where extensive areas of vernal pool habitat developed over 
long periods of time, unique suites of species specially adapted to the 
unusual conditions of vernal pools have evolved. Fish and other 
predators are among the species excluded by vernal pools' annual 
drying, so vernal pool communities have developed and flourished in the 
absence of many predators. California vernal pools are also renowned 
for their showy displays of wildflowers, blooming in concentric rings 
about the pools in spring. Centres of Plant Diversity, a project of the 
World Wide Fund for Nature (WWF) and IUCN--The World Conservation 
Union, has identified the vernal pools of California and Baja 
California, Mexico, as a center of plant diversity and endemism in 
North America, and considers them to be severely threatened (WWF and 
IUCN 2002).
    Many areas in California and portions of southern Oregon have the 
combination of environmental conditions that favors the development of 
vernal pools (Keeley and Zedler 1998). The climate is of a type 
classified as Mediterranean, with a wet season when rainfall exceeds 
evaporation, filling the pools, and a dry season when evaporation is 
greater, drying the pools. Rainfall is relatively meager even in most 
wet seasons, so erosion by overflowing waters does not dissect the 
topographic irregularities that form vernal pool basins. Temperatures 
during the winter-spring wet season are mild, so plants and animals can 
grow, mature, and reproduce.

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    A second major factor in the development of vernal pools is soil. 
Vernal pools form where there is a soil layer below or at the surface 
that is impermeable or nearly impermeable to water (Smith and Verrill 
1998). Precipitation and surface runoff become trapped or ``perched'' 
above this layer. In California, the restrictive soil layers underlying 
vernal pools are of four main types--hardpans, claypans, volcanic 
flows, and non-volcanic rock. Volcanic flows include basaltic lavas and 
cemented mudflows, and are most common along the lower western slope of 
the Sierra Nevada. Hardpans are formed by leaching, redeposition, and 
cementing of silica minerals from high in the soil profile to a lower 
(``B'') horizon (Hobson and Dahlgren 1998, Smith and Verrill 1998). 
Claypans are formed by another redeposition process--fine clay 
particles are transported to the B horizon and accumulate there. 
Claypans may also be augmented by redeposition of saline or alkaline 
compounds. Hardpans and claypans both develop gradually over thousands 
of years, and can be a meter (yard) or more thick. Smith and Verrill 
(1998) list many of the soil series associated with vernal pools in the 
Central Valley.
    A third factor, related to soil and climate, is topography or 
relief. Vernal pools typically occur in landscapes that, at a broad 
scale, are shallowly sloping or nearly level, but on a fine scale may 
be quite bumpy. Complex micro-relief results in shallow, undrained 
depressions that form vernal pools. Some vernal pool landscapes are 
dotted with numerous, rounded soil mounds, referred to as mima mounds, 
after the well-developed mounds of the Mima Prairie in Thurston County, 
Washington (Scheffer 1947). Scientists still argue about the origins of 
these mounds, which have been attributed to forces as disparate as 
gophers acting over millennia (Scheffer 1947, Cox and Gakahu 1983) and 
the pressures of soil swelling and shrinkage during wetting and drying 
cycles (Hallsworth et al. 1955, Hobson and Dahlgren 1998)--as well as 
other hypotheses, many much less plausible. Focusing on the troughs 
rather than the mounds, Californians long referred to vernal pools as 
``hog wallows,'' but unlike the buffalo wallows of the Great Plains, 
these wetlands have little to do with hogs or wallowing. From the air, 
vernal pool landscapes often show characteristic patterning, produced 
by plant responses to mound and trough micro-relief. This patterning 
has allowed detailed mapping of vernal pool habitats throughout 
California's Central Valley and adjacent areas (Holland 1998).
    Vernal pools come in a variety of shapes and sizes, from a square 
meter (yard) to a hectare (2.5 ac) or more. Some larger vernal 
wetlands, such as the 36 ha (90 ac) Olcott Lake in the Jepson Prairie 
Preserve in Solano County, are also referred to as vernal lakes or 
playa pools or lakes. Playa pools with high alkalinity are termed 
alkali sinks. These larger wetlands contain many of the same animals 
and plants of smaller vernal pools, including many rare and endangered 
species.
    Since appropriate combinations of climate, soil, and topography 
often occur over continuous areas rather than in isolated spots, vernal 
pools in California, particularly in the Central Valley, tend to occur 
in clusters, called ``complexes.'' A landscape that supports a vernal 
pool complex is typically a grassland, with areas of obstructed 
drainage that form the pools. Vernal pools can also be found in a 
variety of other habitats, including woodland, desert, and chaparral. 
The pools may be fed or connected by low drainage pathways called 
``swales.'' Swales are often themselves seasonal wetlands that remain 
saturated for much of the wet season, but may not be inundated long 
enough to develop strong vernal pool characteristics. Vernal pool 
complexes have historically been considered poor farmland, because of 
their shallow, seasonally saturated or inundated and sometimes alkaline 
soils, and their root-restricting subsurface layer. For the same 
reasons, trees are relatively rare in most vernal pool complexes.
    California's vernal pools begin to fill with the fall and winter 
rains. Before ponding occurs, there is a period during which the soil 
is wetted and the local water table may rise. Some pools have a 
substantial watershed that contributes to their water inputs; others 
may fill almost entirely from rain falling directly into the pool 
(Hanes and Stromberg 1998). Although exceptions are not uncommon, the 
watershed generally contributes more to the filling of larger or deeper 
pools, especially playa pools. Even in pools filled primarily by direct 
precipitation, Hanes and Stromberg (1998) report that subsurface 
inflows from surrounding soils can help dampen water level fluctuations 
during late winter and early spring. Vernal pools exhibit four major 
phases--the wetting phase, when vernal pool soils become saturated; the 
aquatic phase, when a perched water table develops and the vernal pool 
contains water; a water-logged drying phase, when the vernal pool 
begins loses water as a result of evaporation and loss to the 
surrounding soils but soil moisture remains high; and the dry phase, 
when the vernal pool and underlying soils are completely dry (Keeley 
and Zedler 1998). Upland areas associated with vernal pools are also an 
important source of nutrients to vernal pool organisms (Wetzel 1975). 
Vernal pool habitats derive most of their nutrients from detritus which 
is washed into the pool from adjacent uplands, and these nutrients 
provide the foundation for vernal pool aquatic communities food chain. 
Detritus is a primary food source for the vernal pool crustaceans 
addressed in this proposed rule (Eriksen and Belk 1999).
    Both the amount and timing of rainfall in California vary greatly 
from year to year. As a result, pools may fill to different extents at 
different times. The duration of ponding of vernal pools also varies, 
and in certain years some pools may not fill at all. Many 
characteristics of vernal pool plants and animals are adaptations to 
the highly variable and unpredictable nature of vernal pools (Holland 
1976, Holland and Dains 1990, King et al. 1996, Hanes and Stromberg 
1998).
    California's vernal pools are rich in species composition compared 
to vernal pools worldwide and contain many species that are endemic to 
the region (found nowhere else). In addition, while most of 
California's grasslands are now dominated by non-native grasses and 
other introduced plants, vernal pools remain a haven for native 
species. Invasive non-native plants have been introduced into 
California and have so successfully spread and reproduced in upland 
habitats that it is not unusual for non-natives to account for a third 
of the species and more than 90 percent of the biomass in a California 
grassland. Vernal pools have dramatically resisted this invasion with 
75 to 95 percent of plant species found in vernal pools being native; 
and natives dominate in biomass as well as number (Holland and Jain 
1978, Jokerst 1990, Spencer and Rieseberg 1998). Vernal pool 
communities dominated by natives persist even though they are 
surrounded by seas of grassland raining the seed of non-native plants. 
Vernal pool plant communities are able to resist invasion because of 
the severe ecological constraints on plants living in vernal pool 
environments.
    The animal communities that live in vernal pools also contain 
diverse groups of highly specialized species. The freshwater crustacean 
communities of vernal pools are particularly well developed (Simovich 
1998). The most visible crustaceans in vernal pools are the large 
branchiopods (literally, ``gill-

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foots''), about 27 species in California, of which perhaps 10 are 
endemic (Helm 1998, Belk and Fugate 2000) and 6 are federally listed as 
threatened or endangered. The large branchiopods are easily visible to 
the naked eye, ranging up to 5 centimeters (cm) (2 inches (in)) in 
length, depending on the species. They include the fairy shrimps 
(Anostraca), tadpole shrimps (Notostraca), and clam shrimps 
(Conchostraca). Smaller crustaceans that are common in California 
vernal pools, many large enough to see without magnification, are water 
fleas (Branchiopoda--Cladocera), copepods (Copepoda), and seed shrimp 
(Ostracoda).
    Amphibians and many insect species also live in vernal pools. The 
Pacific tree frog (chorus frog) (Hyla (Pseudacris) regilla) and western 
toad (Bufo boreas) are common and abundant in and around vernal pools. 
Two rarer amphibians native to vernal pools are the California tiger 
salamander (Ambystoma californiense) and the western spadefoot toad 
(Scaphiopus (Spea) hammondii) (Morey 1998). While dispersing bullfrogs 
(Rana catesbeiana), which are not native to California, are sometimes 
found in vernal pools, they do not successfully breed there because 
bullfrog tadpoles require two years to mature and cannot survive the 
dry season. These voracious introduced predators will sometimes be 
found resting and feeding in vernal pools close to more permanent 
water, frequently associated with human modifications of the landscape. 
Fish likewise do not inhabit vernal pools, except where temporarily 
introduced by humans (e.g., mosquitofish (Gambusia sp.)) or by flooding 
of permanent waters.
    The insect fauna of vernal pools is numerous, varied and primarily 
native, including aquatic beetles (Coleoptera--Dytiscidae, 
Hydrophilidae, Gyrinidae, Halipidae, Hydraenidae), aquatic bugs, 
including backswimmers (Hemiptera--Notonectidae), water boatmen 
(Corixidae), and water striders (Gerridae), springtails (Collembola), 
mayflies (Ephemeroptera), dragonflies and damselflies (Odonata), and 
various flies with aquatic larvae, including midges (Diptera--
Chironomidae), crane flies (Tipulidae) and mosquitoes (Culicidae). 
Rogers (1998) found that mosquitoes generally made up less than 2 
percent of the total macroscopic invertebrate population in natural and 
two-year old constructed pools--perhaps because many of the other 
insects listed above are predators. Vernal pool crustaceans are an 
important food source for a number of aquatic and terrestrial species. 
Aquatic predators include insects such as backswimmers (Family 
Notonectidae) (Woodward and Kiesecker 1994), predaceous diving beetles 
and their larvae (Family Dystictidae), and dragonflies and damselfly 
larvae (Order Odonate). Vernal pool tadpole shrimp are another 
significant predator of fairy shrimp.
    The plants, invertebrate and vertebrate animals of vernal pools, 
and vernal pool landscapes in general, are important providers of food 
and habitat for waterfowl, shorebirds, wading birds, toads, frogs, and 
salamanders (Proctor et al. 1967, Krapu 1974, Swanson 1974, Morin 1987, 
Simovich et al. 1991, Silveira 1996). There is evidence that vernal 
pool crustaceans were used as a food source for Native Americans in 
California's Central Valley (Silveira 1998). During the spring, 
waterfowl feed on vernal pool crustaceans and other invertebrates, 
which are sources of protein and calcium needed for migration and egg-
laying (Proctor et al. 1967, Silveira 1998). Vernal pool complexes 
contribute to continuity of wetland habitats along the Pacific Flyway 
(a major bird migration route). Many species feed or nest near vernal 
pools, for example, cliff swallows (Hirundo fulva) glean mud from 
vernal pool beds for their nests, lesser nighthawks (Chordeiles 
acutipennis) nest in dry vernal pool beds, burrowing owl (Athene 
cunicularia) and gopher (Thomomys sp.) burrows are found in mima 
mounds, and many species graze or hunt along vernal pool shorelines. 
Before their populations were nearly eliminated by hunting and habitat 
alteration, elk (Cervus sp.) and pronghorn antelope (Antilocarpa 
americana) undoubtedly grazed vernal pool landscapes, and have been 
replaced by cattle. Fishing net weights found near vernal pools 
suggests that California's first human populations also made use of 
vernal pool resources, as do hunters today (Silveira 1998).

Classification of Vernal Pools

    The variability of vernal pool types has led many researchers to 
try and classify these ephemeral habitats. (i.e., Holland (1986), 
Sawyer and Keeler-Wolf (1995), Ferren et al. (1996), Smith and Verrill 
(1998)). Most of these efforts have focused on classifying vernal pools 
based on the factors that influence variation in their physical 
features. Primary physical features that influence vernal pool size, 
depth, and soil and water chemistry include soil type, geologic 
formation, and landform. Landforms are physical attributes of the 
landscape resulting from geomorphological processes such as erosion and 
deposition, and include features such as alluvial terraces and basins; 
and volcanic mudflows and lava flows.
    The types and kinds of species that are found in vernal pools are 
largely determined by these physical factors, including pool size, 
depth, area, and water and soil chemistry (Holland and Griggs 1976, 
Zedler 1987, Holland and Dains 1990, Eng et al. 1990, Simovich 1998). 
The physical characteristics of the vernal pool influences the life 
history characteristics of vernal pool species, such as the speed with 
which a species can mature and reproduce, the amount of soil moisture 
required for germination of plant seeds or hatching of invertebrate 
eggs or cysts, as well as tolerance to turbidity, total dissolved 
solids, and other aspects of vernal pool water chemistry.
    Sawyer and Keeler-Wolf (1995) classified vernal pools according to 
a number of physical, geographic, and biological characteristics. They 
identified several general vernal pool types which correspond to the 
nature of the impermeable layer that underlay the vernal pool and 
assisted the pool to form. The vernal pools were identified as Northern 
Hardpan, Northern Claypan, Northern Basalt Flow, Northern Volcanic 
Mudflow, and Northern Ashflow vernal pools. Northern Hardpan vernal 
pools are generally formed on alluvial terraces with silicate-cement 
soil layers. These pool types are generally on acidic soils, and 
exhibit well developed mima mound topography found on the eastern 
margins of the Central Valley. Northern Claypan vernal pools are 
generally formed on impermeable surfaces created by an accumulation of 
clay particles. These pool types are often found on basin and basin rim 
landforms and tend to occur in the central portion of the Central 
Valley and tend to be alkaline. Vernal pools identified as Northern 
Volcanic Mudflow, Northern Basalt Flow, and Northern Volcanic Ashflow, 
are generally formed by an impervious bedrock layer of volcanic origin. 
These pool types are found on the eastern and coastal portions of the 
Central Valley, and tend to be small and restricted in distribution. 
Northern Basalt Flow vernal pools occur at greater elevations than 
other vernal pool types.

Vernal Pool Crustaceans Background

    Conservancy fairy shrimp (Branchinecta conservatio), longhorn fairy 
shrimp (Branchinecta longiantenna), and vernal pool fairy shrimp 
(Branchinecta lynchi) are members of the aquatic crustacean order 
Anostraca. Vernal pool tadpole shrimp

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(Lepidurus packardi) is a member of the aquatic crustacean order 
Notostraca. Vernal pool fairy shrimp are found in California and 
southern Oregon while the other three shrimp species are found only in 
California. These species have all evolved similar adaptations to the 
unique habitat conditions of their vernal pool habitats. The general 
appearance and life history characteristics of these four species will 
be described in combination below.
    Longhorn fairy shrimp, vernal pool fairy shrimp, and Conservancy 
fairy shrimp (fairy shrimp) have delicate elongate bodies, large 
stalked compound eyes, and 11 pairs of phyllopods, or gill-like 
structures that also serve as legs. They swim or glide gracefully 
upside down by means of complex beating movements that pass in a wave-
like anterior to posterior direction. Fairy shrimp are filter feeders, 
and consume algae, bacteria, protozoa, rotifers, and bits of detritus 
as they move through the water. The second pair of antennae in fairy 
shrimp adult males are greatly enlarged and specialized for clasping 
the females during copulation. The females carry eggs in an oval or 
elongate ventral sac (brood sac). Once fertilized, the eggs are coated 
with a protective protein layer that allows them to withstand heat, 
cold, and prolonged dehydration. The fully developed eggs are either 
dropped to the pool bottom or remain in the brood sac until the female 
dies and sinks. These dormant eggs are also known as cysts, and they 
can remain viable in the soil for decades after deposition (Eriksen and 
Belk, 1999). When the pools refill in the same or subsequent seasons, 
some, but not all, of the cysts may hatch (Eriksen and Belk, 1999). The 
cyst bank in the soil may consist of cysts from several years of 
breeding. The cysts that hatch may do so within days after the vernal 
pools fill, and rapidly develop into adults within weeks. In pools that 
persist for several weeks to a few months, fairy shrimp may have 
multiple hatches during a single season.
    Vernal pool tadpole shrimp have dorsal compound eyes, a large 
shield-like carapace (shell) that covers most of their body and a pair 
of long cercopods or appendages at the end of the last abdominal 
segment. They are primarily benthic (living on the bottoms of the 
pools) animals that swim with their legs down. Vernal pool tadpole 
shrimp climb or scramble over objects, and plow along bottom sediments 
as they forage for food. Their diet consists of organic detritus 
(decaying matter) and living organisms, such as fairy shrimp and other 
invertebrates (Fryer 1987). The females deposit eggs on vegetation and 
other objects on the pool bottom. Like fairy shrimp, vernal pool 
tadpole shrimp pass the summer months as dormant cysts in the soil. 
Some of the cysts hatch as the vernal pools are filled with rainwater 
in the next or subsequent seasons, while other cysts may remain dormant 
in the soil for many years. When winter rains refill inhabited pools, 
tadpole shrimp reestablish from dormant cysts and may become sexually 
mature within three to four weeks after hatching (Ahl 1991, Helm 1998). 
Mature adults may be present in pools until the habitats dry up in the 
spring (Ahl 1991, Gallagher 1996).
    All of the vernal pool crustacean species addressed in this 
proposed critical habitat designation have evolved unique physical 
adaptations to survive in vernal pools. The timing and duration of wet 
and dry phases can vary significantly from year to year, and in some 
years vernal pools may not inundate at all. In order to take advantage 
of the short inundation phase, vernal pool crustaceans have evolved 
short reproduction times and high reproductive rates. Most of the 
species addressed in this proposed rule hatch within a few days after 
their habitats fill with water, and can start reproducing within a few 
weeks (Eng et al. 1990, Helm 1998, Eriksen and Belk 1999). Vernal pool 
crustaceans can complete their entire life cycle in a single season, 
and some species may complete several life cycles. Vernal pool 
crustaceans can also produce thousands viable cysts when environmental 
conditions are favorable.
    To survive the prolonged heat and dessication of the vernal pool 
dry phase, vernal pool crustaceans have developed a dormant stage. 
After vernal pool crustacean eggs are fertilized in the female's brood 
sac, the embryos develop a thick, usually multi-layered shell. When 
embryonic development reaches a late stage, further maturation stops, 
metabolism is drastically slowed, and the egg, now referred to as a 
cyst, enters a dormant state called diapause. The cyst is then either 
dropped to the pool bottom or remains in the brood sac until the female 
dies and sinks. Once the cyst is desiccated, it can withstand 
temperatures near boiling (Carlisle 1968), fire (Wells et al. 1997), 
freezing, and anoxic conditions without damage to the embryo. The cyst 
wall cannot be affected by digestive enzymes, and can be transported in 
the digestive tracts of animals without harm (Horne 1967). Most fairy 
shrimp cysts can remain viable in the soil for a decade or longer (Belk 
1998).
    Although the exact signals that cause crustacean cysts to hatch are 
unknown, factors such as soil moisture, temperature, light, oxygen, and 
osmotic pressure may trigger the embryo's emergence from the cyst 
(Brendonck 1996). Because the cyst contains a well developed embryo, 
the animal can quickly develop into a fully mature adult. This allows 
vernal pool crustaceans to reproduce before the vernal pool enters the 
dry phase, sometimes within only a few weeks (Helm 1998, Eriksen and 
Belk 1999). In some species, cysts may hatch immediately without going 
through a dormant stage, if they are deposited while the vernal pool 
still contains water. These cysts are referred to as quiescent, and 
allow the vernal pool crustacean to produce multiple generations in a 
single wet season as long as their habitat remains inundated.
    Another important adaptation of vernal pool crustaceans to the 
unpredictable conditions of vernal pools is the fact that not all of 
the dormant cysts hatch in every season. Simovich and Hathaway (1997) 
found that only 6 percent of San Diego fairy shrimp cysts hatched after 
initial hydration, and only 0.18 percent of Riverside fairy shrimp 
cysts hatched. The cysts that don't hatch remain dormant and viable in 
the soil. These cysts may hatch in a subsequent year, and form a cyst 
bank much like the seed bank of annual plants. The cyst bank may be 
comprised of cysts from several years of breeding, and large cyst banks 
of viable resting eggs in the soil of vernal pools containing fairy 
shrimp have been well documented (Belk 1998). Based on a review of 
other studies (e.g., Belk 1977, Gallagher 1996, Brendonck 1996), 
Simovich and Hathaway (1997) concluded that species inhabiting more 
unpredictable environments, such as smaller or shorter lived pools, are 
more likely to have a smaller percent of their cysts hatch after their 
vernal pool habitats fill with water. This strategy reduces the 
probability of complete reproductive failure if a vernal pool dries up 
prematurely. This kind of ``bet-hedging strategy'' has been suggested 
as a mechanism by which rare species may persist in unpredictable 
environments (Chesson and Warner 1981, Chesson and Huntly 1989, Ellner 
and Hairston 1994).
    Although the vernal pool crustaceans, and particularly the fairy 
shrimp, addressed in this proposed rule are not often found in the same 
vernal pool at the same time, when coexistence does occur, it is 
generally in deeper, longer lived pools (Eng et al. 1990, Thiery 1991, 
Gallagher 1996, Simovich 1998). In larger pools, closely related 
species of fairy shrimp may coexist by hatching at different 
temperatures, and by

[[Page 59888]]

developing at different rates (Thiery 1991, Hathaway and Simovich 
1996). Vernal pool crustacean species may also be able to coexist by 
utilizing different physical portions of the vernal pool, or by eating 
different food sources (Daborn 1978, Mura 1991, Hamer and Appleton 
1991, Thiery 1991).
    The primary historic dispersal mechanisms for the vernal pool 
crustaceans probably consisted of large scale flooding resulting from 
winter and spring rains, and dispersal by migratory birds. As a result 
of widespread flood control and agricultural water diversion projects 
developed during the twentieth century, large scale flooding is no 
longer a major form of dispersal for the vernal pool crustaceans. When 
being dispersed by migratory birds, the eggs of these crustaceans are 
either ingested (Krapu 1974, Swanson 1974, Driver 1981, Ahl 1991) and/
or adhere to the bird's legs and feathers where they are transported to 
new habitats. Cysts may also be dispersed by a number of other species, 
such as salamanders, toads, cattle, and humans (Eriksen and Belk 1999).
    The vernal pool crustaceans addressed in this proposed rule are 
generally confined to habitats that are low to moderate in alkalinity 
and dissolved salts, when compared with other aquatic systems (Ericksen 
and Belk 1999). Although potentially moderated by soil type, vernal 
pools are generally unbuffered and exhibit wide fluctuations in pH and 
dissolved oxygen (Keeley and Zedler 1998). Vernal pool water ion 
concentrations, such as sodium, potassium, calcium, chlorine, and 
magnesium, also experience large daily and seasonal variations. These 
variations are due to the concentration of ions due to evaporation, and 
the dilution of ions with additional rainfall throughout the wet season 
(Barclay and Knight 1981). How vernal pool crustacean species adapt to 
these fluctuations in water chemistry varies. Definitive conclusion on 
why the species has certain water chemistry habitat preferences is 
generally unknown due to the anecdotal nature of observations.
    Additional information specific to each of the four individual 
vernal pool crustacean species described in this proposed rule is 
provided below.

Conservancy Fairy Shrimp

    Conservancy fairy shrimp were first described in 1990 by Eng, Belk, 
and Eriksen. The type specimens were collected in 1982 at Olcott Lake, 
Solano County, California. Conservancy fairy shrimp are currently known 
from only eight disjunct areas--Vina plains and vicinity in southern 
Tehama and northern Butte County; Jepson Prairie in Solano County; 
Suisun Slough in southern Solano County; Sacramento National Wildlife 
Refuge in Glenn County; near Caswell Memorial State Park in Stanislaus 
County; Haystack Mountain Area in eastern Merced County; San Luis 
National Wildlife Refuge Complex in central Merced County, and the 
Mutau Flat area in the Los Padres National Forest area of northern 
Ventura County.
    Conservancy fairy shrimp look similar to other fairy shrimp 
species, but can be distinguished by characteristics of the male second 
antenna. The second antennae of Conservancy fairy shrimp males have a 
distal segment which is about 30 percent shorter than the basal 
segment, and has a tip bent medially about 90 degrees (Eng et al. 
1990). The female brood pouch is tapered at each end, typically extends 
to abdominal segment 8, and has a terminal opening (Eng et al. 1990). 
Males may be from 14 to 27 millimeters (mm) (0.6 to 1.1 in) in length, 
and females have been measured between 14.5 and 23 mm (0.6 and 0.9 in) 
long.
    Further discussion on the life history and habitat requirements of 
Conservancy fairy shrimp can be found in the final rule to list this 
species (59 FR 48136).

Longhorn Fairy Shrimp

    Longhorn fairy shrimp were first collected in 1937, but were not 
formally described until 1990 by Eng, Belk, and Eriksen. The type 
specimen was collected from a sandstone outcrop pool on the Souza Ranch 
in Contra Costa County, California. Longhorn fairy shrimp are extremely 
rare, and are only known from three widely separated locations; the 
Altamont Pass area in Contra Costa and Alameda counties; the western 
and northern boundaries of Soda Lake on the Carrizo Plain in San Luis 
Obispo County; and Kesterson National Wildlife Refuge in the San 
Joaquin Valley in Merced County. Vernal pool crustacean surveys 
conducted by Sugnet (1993) found only 3 occurrences of longhorn fairy 
shrimp out of 3,092 locations surveyed, and Helm (1998) found 
occurrences of longhorn fairy shrimp in only 9 of 4,008 wetlands 
sampled.
    Longhorn fairy shrimp are distinguished from other fairy shrimp by 
the male's very long second antennae, which is about twice as long, 
relative to its body, as the second antennae of other species of 
Branchinecta. Longhorn fairy shrimp antennae range from 6.7 to 10.4 mm 
(0.3 to 0.4 in) in length (Eriksen and Belk 1999). Females can be 
recognized by their cylindrical brood pouch, which extends to below 
abdominal segments 6 or 7. Mature males have been measured between 12 
and 21 mm (0.5 to 0.8 in) in length, and females range from 13.3 to 
19.8 mm (0.5 to 0.8 in) in length (Eng et al. 1990).
    Further discussion on the life history and habitat requirements of 
longhorn fairy shrimp can be found in the final rule to list this 
species (59 FR 48136).

Vernal Pool Fairy Shrimp

    Vernal pool fairy shrimp were first described by Eng et al. in 1990 
from a type specimen that was collected in 1982 at Souza Ranch, Contra 
Costa County, California. The species occurs in disjunct fragmented 
habitats distributed across the Central Valley of California from 
Shasta County to Tulare County and the central and southern coast 
ranges from northern Solano County to Ventura County, California. 
Additional disjunct populations have been identified in southern 
California and in Oregon. In Oregon, the species' distribution is 
limited to the vicinity of an approximately 82.9 square kilometer (sq 
km) (32 square mile (sq mi)) area known as the Agate Desert in Jackson 
County, north of Medford. In southern California the distribution is 
equally limited with populations occurring in three areas in Riverside 
County.
    Vernal pool fairy shrimp are characterized by the presence and size 
of several bulges on the male's antenna, and by the female's short, 
pyriform or pear shaped, brood pouch. Vernal pool fairy shrimp vary in 
size, ranging from 11 to 25 mm (0.4 to 1.0 in) in length (Eng et al. 
1990).
    Vernal pool fairy shrimp are currently found in 27 counties across 
the Central Valley and coast ranges of California, inland valleys of 
southern California, and southern Oregon. Although vernal pool fairy 
shrimp are distributed more widely than most other fairy shrimp 
species, they are generally uncommon throughout their range, and rarely 
abundant where they do occur (Eng et al. 1990, Eriksen and Belk 1999).
    Further discussion on the life history and habitat requirements of 
vernal pool fairy shrimp can be found in the final rule to list this 
species (59 FR 48136).

Vernal Pool Tadpole Shrimp

    Vernal pool tadpole shrimp were initially described by Simon in 
1886, and named Lepidurus packardi. After subsequent reclassification 
by Longhurst (1955), the species was given a subspecies status based 
primarily on the lack of apparent geographic boundaries between L. apus 
and L. packardi populations. Lynch (1972)

[[Page 59889]]

resurrected L. packardi to full species status based on further 
examination of specimens and this is the currently accepted taxonomic 
status of vernal pool tadpole shrimp. Vernal pool tadpole shrimp 
inhabit sites in California's Central Valley and San Francisco Bay 
area. The geographic range of this species includes disjunct 
populations found in the Central Valley from Shasta County to northern 
Tulare County and in the central coast range from Solano County to 
Alameda County.
    Vernal pool tadpole shrimp are distinguished by a large, shield-
like carapace, or shell, that covers the anterior half of their body. 
Vernal pool tadpole shrimp have 30 to 35 pairs of phyllopods, a 
segmented abdomen, paired cercopods or tail-like appendages, and fused 
eyes. Vernal pool tadpole shrimp will continue to grow as long as their 
vernal pool habitats remain inundated, in some cases for six months or 
longer. They periodically shed their shells, which can often be found 
along the edges of vernal pools where vernal pool tadpole shrimp occur. 
Mature vernal pool tadpole shrimp range in size from 15 to 86 mm (0.6 
to 3.4 in) in length.
    Vernal pool tadpole shrimp have relatively high reproductive rates. 
Ahl (1991) found that fecundity increases with body size. Large 
females, greater than 20 mm (0.8 in) carapace length, could deposit as 
many as 6 clutches, averaging 32 to 61 eggs per clutch, in a single wet 
season.
    Further discussion on the life history and habitat requirements of 
vernal pool tadpole shrimp can be found in the final rule to list this 
species (59 FR 48136).
    The habitat of the four vernal pool crustaceans is imperiled by a 
variety of activities, primarily by urban development, water supply and 
flood control activities, and conversion of land to agricultural use. 
Habitat loss occurs from direct destruction and modification of pools 
due to filling, grading, discing, leveling, and other activities, as 
well as modification of surrounding uplands. Vernal pool crustaceans 
and their habitat also are threatened by altered flood regimes, 
degraded water quality, siltation, erosion, grazing, improper burning, 
military operations, off-road vehicles, pollution, vandalism, road and 
trail maintenance, and introduction of non-native predators. Further 
discussion on threats to the vernal pool crustaceans can be found in 
the final rule to list these species (59 FR 48136).

Vernal Pool Plants Background

    The vernal pool plants described in this proposed rule have 
developed a suite of highly specialized adaptations which allow them to 
survive in vernal pool habitats. All eleven species are annuals, 
meaning they germinate, grow, and reproduce within a single year. This 
allows the vernal pool plants to complete their life cycles during the 
relatively short inundation and drying periods of their vernal pool 
habitat.
    Another adaptation of vernal pool plants is production of dormant 
seeds. This adaptation allows vernal pool plants to survive the hot 
summer months in the soil. The seeds may remain viable in the soil for 
many years. The number of plants present above ground may fluctuate 
dramatically from year to year. However, much of the population of 
these species exists as seeds in the soil. Vernal pool plant seeds 
generally germinate after winter rains in response to a complex set of 
environmental cues that are not well understood, but that generally 
include temperature and soil moisture. Specific germination cues differ 
greatly among species and are discussed in more detail in the 
individual species descriptions below. Not all of the dormant seeds 
will germinate in any given year. This strategy reduces the probability 
of local extirpation if environmental conditions change, for example if 
a vernal pool dries up prematurely. This kind of ``bet-hedging 
strategy'' has been suggested as a mechanism by which rare species may 
persist in unpredictable environments (Chesson and Warner 1981, Chesson 
and Huntly 1989, Ellner and Hairston 1994).
    Tolerance to inundation differs greatly among species (Zedler 
1987). The zonation of vernal pool plants which forms the 
characteristic rings of flowers around vernal pools is a result of this 
differential tolerance to inundation. Species that are the least 
tolerant to inundation grow along the margins of the pool, while those 
that can tolerate extended periods of inundation grow in the center of 
the pools.
    Information on the appearance and life history of each of the 
eleven individual vernal pool plant species described in this proposed 
rule is provided below.

Butte County Meadowfoam

    Butte County meadowfoam (Limnanthes floccosa ssp. californica) was 
first collected in 1917 at a site 16 kilometers (km) (10 mi)) north of 
Chico (Service 1991b), although it was recognized as a separate 
subspecies at that time. Kalin-Arroyo (1973) determined that Butte 
County meadowfoam was a distinct taxon and gave it the scientific name 
Limnanthes floccosa ssp. californica. The type locality is in Butte 
County between Chico and Oroville, near the intersection of state 
Highway 99 and Shippee Road (Kalin-Arroyo 1973).
    Butte County meadowfoam is a small annual of the meadowfoam or 
false mermaid family (Limnanthaceae). It has erect stems less than 25 
cm (9.8 in) tall. The stem and leaves are densely pubescent (covered 
with short hairs). The alternate leaves are pinnately compound (divided 
into distinct segments which are arranged featherlike on either side of 
a rachis), up to 8 cm (3.1 in) long, and consist of five to eleven 
leaflets on a long petiole. A single flower arises in the axil (angle 
between the base of a leaf and the stem) of each upper leaf. The 
flowers are white with yellow veins, cup or bowl-shaped, and consist of 
five petals, five sepals, five pistils (female reproductive structures 
of a flower), and ten stamens (male reproductive structures of a 
flower) on a long flower stalk (Kalin-Arroyo 1973, McNeill and Brown 
1979, Ornduff 1993b).
    Butte County meadowfoam seedlings can tolerate short periods of 
submergence (Jokerst 1989, Dole and Sun 1992). The seedlings develop 
into rosettes (clusters of leaves near the ground), which do not begin 
producing flowering stems immediately (McNeill and Brown 1979, Ritland 
and Jain 1984). Butte County meadowfoam typically begins flowering in 
February, reaches peak flowering in March, and may continue into April 
if conditions are suitable. Nutlets are produced in March and April, 
and the plants die back by early May (Jokerst 1989, Dole and Sun 1992).
    Butte County meadowfoam is predominantly self fertilized (Dole and 
Sun 1992). Nutlets of Butte County meadowfoam apparently are dispersed 
by water; they can remain afloat for up to 3 days (Hauptli et al. 
1978). Limnanthes taxa that grow in wet sites have larger tubercles 
than those adapted to dry sites. Hauptli et al. (1978) speculated that 
the tuberculate surface of such nutlets may aid in flotation by 
trapping air. However, most meadowfoam nutlets are dispersed only short 
distances. Thus, Butte County meadowfoam nutlets would not be expected 
to disperse beyond their pool or swale of origin. Birds and livestock 
are potential sources of long-distance seed dispersal, but specific 
instances of dispersal have not been documented (Jain 1978).
    Butte County meadowfoam has always been confined to the Butte 
County (Keeler-Wolf et al. 1998). In her original description, Kalin-
Arroyo

[[Page 59890]]

(1973) mentioned six collections, including the type locality. Five of 
those ranged from the original collection site southeast to Oroville, 
and the sixth was from Table Mountain north of Oroville. However, 
Jokerst (1983) did not find Butte County meadowfoam on Table Mountain 
and later suggested that the specimen had been misidentified (Service 
1992a).
    All 13 of the occurrences described by the CNDDB (2001) had been 
reported by 1988 (Kalin-Arroyo 1973, McNeill and Brown 1979, Dole 1988, 
Jokerst 1989). Five were in northern and northeastern Chico near the 
municipal airport, four (including the type locality) were from the 
area around Shippee (northwest of Oroville), and three from 
southeastern Chico. The other occurrence, northeast of the town of 
Nord, contained only one plant that was of questionable identity (CNDDB 
2001). However, the area indicated would be in the same vicinity as the 
1917 collection.
    Jokerst (1989) identified ``north'' and ``south'' races of Butte 
County meadowfoam in the Chico ``sphere of influence'' based on 
morphology. Later, in studies of enzyme systems, Dole and Sun (1992) 
confirmed that these races differed genetically. They also identified 
genetically distinct races that they called ``northeast'' and 
``southwest,'' with the latter referring to the type locality. They 
found that 96 percent of genetic diversity in Butte County meadowfoam 
existed among populations and that little variability was evident 
within populations. Dole and Sun (1992) used mathematical formulas to 
estimate an average generation time of 2 years for Butte County 
meadowfoam and to predict that a seed would be transferred between 
populations only once every 100 to 200 years. Although considerable 
morphological variability has been observed within populations, it 
apparently is attributable to differences in environmental response by 
plants of the same genetic makeup (Jain 1976, Jokerst 1989).
    Two occurrences of Butte County meadowfoam have been extirpated, 
one each in northern and southeastern Chico (Jokerst 1989, Dole and Sun 
1992, Service 1992a, CNDDB 2001). Some of the other 11 occurrences have 
been reduced in extent (CNDDB 2001). The most recent reports are from 
1992 and additional losses could have occurred since then.
    Sawyer and Keeler-Wolf (1995) mentioned Butte County meadowfoam as 
only associated with Northern Basalt Flow vernal pools; however, this 
pool type was likely based on the erroneous Table Mountain occurrence. 
Butte County meadowfoam occurs primarily in vernal swales and to a 
lesser extent on the margins of vernal pools (Kalin-Arroyo 1973, Dole 
1988, Jokerst 1989, BioSystems Analysis, Inc. 1993, CNDDB 2001). Swales 
vary in width from narrow channels to broad, pool-like areas (LSA 
Associates, Inc. 1994). They may connect in branching, tree-like 
patterns or in net-like patterns around low mounds. Occupied swales are 
inundated periodically by water from the surrounding uplands, causing 
the soil to become saturated. However, Butte County meadowfoam does not 
persist in pools or swales that are inundated for prolonged periods or 
remain wet during the summer months, nor in drainages where water flows 
swiftly (Jokerst 1989, Kelley and Associates Environmental Sciences 
1993). BioSystems Analysis Inc. (1993) only found it in the wettest 
swales in 1992 during the drought. Occupied swales are less than 10 cm 
(3.9 in) deep (LSA Associates, Inc. 1994) and pools are typically less 
than 30 m (100 ft) long (Jokerst 1989). In both swales and pools, Butte 
County meadowfoam may grow along the edges or in the bottom (Kalin-
Arroyo 1973, Jokerst 1989). In a study of the Shippee area population 
(BioSystems Analysis, Inc. 1993) Butte County meadowfoam was found 
growing more often on pool margins than in the bottom of pools but the 
pattern was reversed in swales, with the plants more often growing in 
the center. It typically occurs in long, narrow bands in connected 
swales or on pool margins but can be found in irregular clusters in 
isolated drainages (Crompton 1993). Butte County meadowfoam has been 
found occasionally in disturbed areas such as drainage ditches, 
firebreaks, and graded sites (McNeill and Brown 1979, Jokerst 1989, 
Kelley and Associates Environmental Sciences 1992, BioSystems Analysis, 
Inc. 1993, Kelley and Associates Environmental Sciences 1993).
    Further discussion on Butte County meadowfoam's life history and 
habitat characteristics can be found in the final rule to list the 
species (62 FR 54807).

Contra Costa Goldfields

    Greene (1888) first described Contra Costa goldfields, as Lasthenia 
conjugens, from specimens collected near Antioch, California. Hall 
(1914) later lumped Contra Costa goldfields in with the common species 
Fremont's goldfields, which at that time was called Baeria fremontii. 
Ferris (1958) proposed the name Baeria fremontii var. conjugens to 
recognize the distinctiveness of L. conjugens. Finally, Ornduff (1966) 
restored Greene's original name and rank, returning this species to the 
genus Lasthenia.
    Contra Costa goldfields is a showy spring annual in the aster 
family (Asteraceae). Its stems are 10 to 30 cm (4 to 12 in) tall, 
somewhat fleshy, and usually are branched. The leaves are opposite and 
narrow; the lower leaves are entire, but stem leaves have one or two 
pairs of narrow lobes. The daisy-like flower heads are solitary (Greene 
1888, Ornduff 1993a).
    As a vernal pool annual, seeds of Contra Costa goldfields would be 
expected to germinate in response to autumn rains, with the plants 
maturing in a single growing season, setting seed, and dying back 
during the summer. However, detailed research on the life cycle has not 
been conducted. Contra Costa goldfields flower from March through June 
(Ornduff 1966, Ornduff 1979, Skinner and Pavlik 1994). The flowers are 
self-incompatible (Crawford and Ornduff 1989). Insect visitors to 
flowers of Lasthenia belong to five orders--Coleoptera, Diptera, 
Hemiptera (true bugs), Hymenoptera (ants, bees and wasps), and 
Lepidoptera (butterflies and moths) (Thorp and Leong 1998). Most of 
these insects are generalist pollinators. Some Lasthenia are pollinated 
by specialist solitary bees (family Andrenidae); including two bee 
species in the subgenus Diandrena (Andrena submoesta and A. puthua) and 
five or six species in the subgenus Hesperandrena (Andrena baeriae, A. 
duboisi, A. lativentris, and two or three undescribed species) (Thorp 
and Leong 1998). The extent to which pollination of Contra Costa 
goldfields depends on host-specific bees or more generalist pollinators 
is currently unknown.
    Seed dispersal mechanisms in Contra Costa goldfields are unknown. 
However, the lack of a pappus or even hairs on the achenes makes wind 
dispersal unlikely (Ornduff 1976). Seed longevity, survival rates, 
fecundity, and other demographic parameters have not been investigated. 
However, as with other vernal pool annuals, population sizes have been 
observed to vary by up to four orders of magnitude from year to year 
(CNDDB 2001).
    By far the greatest concentration of this species is in Solano 
County where Contra Costa goldfields are found in the area east and 
south of the City of Fairfield. Other areas that support populations of 
this species include the central coast between Monterey and Alameda 
counties, including Fort Ord in Monterey County, San Francisco Bay 
National Wildlife Refuge, and near Fremont, in Alameda County. The 
Santa Barbara County occurrence has probably been lost due to habitat 
alteration

[[Page 59891]]

(CNDDB 2001). Contra Costa goldfields also occurs near Manchester in 
Mendocino County, and at Suscol Ridge in Napa County. Another Napa 
County site, Milliken Canyon, contained only a single plant in 1987 and 
may or may not be still in existence (CNDDB 2001). The other existing 
occurrence is near Rodeo in Contra Costa County (CNDDB 2001).
    Further discussion on Contra Costa goldfields' life history and 
habitat characteristics can be found in the final rule to list the 
species (62 FR 33037).

Hoover's spurge

    Hoover's spurge (Chamaesyce hooveri) was originally named Euphorbia 
hooveri based on a specimen collected by Hoover in Yettem, Tulare 
County (Wheeler 1940). Koutnik (1985) placed the species in the genus 
Chamaesyce as Chamaesyce hooveri.
    Hoover's spurge is an annual herb of the spurge family 
(Euphorbiaceae). Hoover's spurge trails along the ground, forming gray-
green mats 5 to 100 cm (2.0 to 39.4 in) in diameter (Broyles 1987, 
Stone et al. 1988). The stems are hairless and contain milky sap. The 
tiny (2 to 5 mm (0.08 to 0.20 in)) leaves are opposite, rounded to 
kidney-shaped, with an asymmetric base and a toothed margin. In the 
genus Chamaesyce, the structures that appear to be flowers actually are 
groups of flowers; each group is referred to as a cyathium (Koutnik 
1993).
    Few details of the life history of Hoover's spurge are known. Seeds 
of Hoover's spurge germinate after water evaporates from the pools; the 
plants cannot grow in standing water (Alexander and Schlising 1997). 
The indeterminate growth pattern allows the plants to continue growing 
as long as sufficient moisture is available. The proportion of 
seedlings surviving to reproduction has not been documented; in years 
of below normal rainfall, seedling survival was characterized as 
``low'' (Stone et al. 1988). The phenology (timing of various stages in 
the life cycle of a plant) varies among years and among sites, even for 
those populations in close proximity (Stone et al. 1988). Populations 
in Merced and Tulare counties typically flower from late May through 
July, whereas those in Stanislaus County and the Sacramento Valley 
flower from mid-June into October (Alexander and Schlising 1997, CNDDB 
2001, J. Silveira USFWS pers. comm.). Seed set apparently begins soon 
after flowering. Seed production has not been quantified or studied in 
relation to environmental factors, but Stone et al. (1988) reported 
that large plants may produce several hundred seeds. Horned larks 
(Eremophila alpestris) have been observed eating seeds of Hoover's 
spurge and thus may assist in seed dispersal (Alexander and Schlising 
1997).
    Demographic data suggest that seeds of Hoover's spurge can remain 
dormant until the appropriate temperature and moisture conditions 
occur. This is evident from the fact that plants can be absent from a 
given pool for up to four years and then reappear in substantial 
numbers. Although certain years appear to be more favorable for 
Hoover's spurge than others, population trends vary from pool to pool, 
even within the same year in the same area. Moreover, a particular year 
may be favorable for Hoover's spurge at one site and unfavorable at 
another. For example, Hoover's spurge was extremely abundant on the 
Vina Plains Preserve in 1995, but reached a 7-year low at Sacramento 
National Wildlife Refuge that year. Five occurrences of Hoover's spurge 
have numbered 5,000 or more plants at their maximum size. Four of those 
five occur on the Vina Plains, and the other occurs in Tulare County 
(Stone et al. 1988, CNDDB 2001).
    Hoover's spurge probably is pollinated by insects. Related species 
in the spurge family are pollinated by flies (Heywood 1978, Stone et 
al. 1988). Also, glands on the plant produce nectar (Wheeler 1941), 
which is attractive to insects. Beetles, flies, bees and wasps, and 
butterflies and moths (order Lepidoptera) have been observed visiting 
the flowers of Hoover's spurge and may potentially serve as pollinators 
(Stone et al. 1988, Alexander and Schlising 1997). Related species in 
the genus Euphorbia typically are cross-pollinated because the female 
flowers on each plant mature before the male (Heywood 1978, Stone et 
al. 1988), which may or may not be the case for Hoover's spurge.
    For decades, Hoover's spurge was known from only three localities--
near Yettem and Visalia in Tulare County, and near Vina in Tehama 
County. Collections were made from these three areas in the late 1930's 
and early 1940's (Wheeler 1941, Munz and Keck 1959, Stone et al. 1988). 
From 1974 through 1987, 21 additional occurrences of Hoover's spurge 
were reported. The majority of these (15) were in Tehama County. One to 
three occurrences were discovered during this period in each of Butte, 
Merced, Stanislaus, and Tulare counties (Stone et al. 1988, CNDDB 
2001).
    The CNDDB (2001) now includes 30 occurrences of Hoover's spurge. In 
addition to those known historically, six occurrences were discovered 
in 1992 (three each in Glenn and Tulare counties). Of the 30 
occurrences, one each in Tehama and Tulare counties are classified as 
extirpated; two others, in Butte and Tehama counties, are ``possibly 
extirpated'' because this species was not observed for two consecutive 
years (Stone et al. 1988, CNDDB 2001). Of the 26 occurrences presumed 
to be extant, only 12 have been observed within the past decade (CNDDB 
2001).
    The main area of concentration for Hoover's spurge is within the 
northeastern Sacramento Valley. The Vina Plains of Tehama and Butte 
counties contains 14 (53.8 percent) of the 26 extant occurrences for 
Hoover's spurge (CNDDB 2001) in an area approximately 91 sq km (35 sq 
mi) in extent (Stone et al. 1988). One other site in the same region is 
near Chico in Butte County. Seven of the extant occurrences are in 
Southern Sierra Foothills Vernal Pool Region, including five in the 
Visalia-Yettem area of Tulare County and two in the Hickman-La Grange 
area of Stanislaus County. Three other occurrences are on the 
Sacramento National Wildlife Refuge in Glenn County, which is in the 
Solano-Colusa Vernal Pool Region. The one other extant occurrence is on 
the Bert Crane Ranch in Merced County, which is within the San Joaquin 
Valley Vernal Pool Region (Keeler-Wolf et al. 1998, CNDDB 2001).
    Further discussion on Hoover's spurge's life history and habitat 
characteristics can be found in the final rule to list the species (62 
FR 14351).

Succulent Owl's-Clover

    Succulent (or fleshy) owl's-clover was first described by Hoover 
(1936a) as Orthocarpus campestris var. succulentus. The type specimen 
had been collected at Ryer, in Merced County. Hoover (1968) 
subsequently raised succulent owl's-clover to the rank of species and 
assigned it the name Orthocarpus succulentus. Chuang and Heckard (1991) 
reconsidered the taxonomy of Orthocarpus and related genera. Based on 
floral morphology (external structure or form), seed morphology, and 
chromosome number, they transferred many species into the genus 
Castilleja. Furthermore, they determined that the appropriate rank for 
succulent owl's-clover was as a subspecies of Castilleja campestris 
(field owl's-clover). The scientific name currently assigned to the 
plant is Castilleja campestris ssp. succulenta (Chuang and Heckard 
1991).
    Succulent owl's-clover is a hemiparasitic (partly parasitic) annual 
herb belonging to the snapdragon family (Scrophulariaceae). It has 
erect or

[[Page 59892]]

decumbent stems up to 30 cm (11.8 in) long. The stems are usually 
unbranched and without hairs. The leaves at the base of the stem are 
small and scalelike, whereas those on the upper stem are lance-shaped, 
not lobed, thick, fleshy, brittle, and easily broken. The bracts (leaf-
like structures in the flowering structure) are green, similar to but 
shorter than the upper leaves, and longer than the flowers. Overall, 
the inflorescence (entire flowering structure of a plant) may occupy as 
much as half of the plant's height (Hoover 1936a, Hoover 1937, Hoover 
1968, Chuang and Heckard 1991, Chuang and Heckard 1993).
    As with many related species, succulent owl's-clover is a 
hemiparasite, meaning that it obtains water and nutrients by forming 
root grafts with other host plants but manufactures its own food 
through photosynthesis (Chuang and Heckard 1991). Research on 
hemiparasitism has focused on related species of Castilleja, but not 
specifically on succulent owl's-clover. Many different plants can serve 
as hosts for a single species or even a single individual of 
Castilleja. Seeds do not require the presence of a host to germinate, 
and form root connections only after reaching the seedling stage. Some 
seedlings can survive to maturity without attaching to a host's roots, 
but in general reproduction is enhanced by root connections (Atsatt and 
Strong 1970).
    The conditions necessary for germination of succulent owl's-clover 
seeds have not been studied, nor has the timing of seed germination 
been documented. Flowering occurs in April and May (Skinner and Pavlik 
1994). Although many related taxa of Castilleja are pollinated by 
generalist bees (Superfamily Apoidea) (Chuang and Heckard 1991), 
succulent owl's-clover is thought to be self-pollinating. Among close 
relatives that do not require insect pollinators, flower structure and 
timing of stigma receptivity maximize the chances for self-
fertilization and seed set. Even so, insects may transfer some pollen 
among individual plants and species occurring in the same area. Self-
pollinating species of Castilleja typically occur as widely scattered 
individuals, rather than in dense colonies (Atsatt 1970). Succulent 
owl's-clover follows this pattern in part, often occurring in many 
pools within a complex but with fewer than 100 plants per pool. 
However, succulent owl's-clover also may occur in large populations 
within a single pool (California Natural Diversity Data Base (CNDDB) 
2001). Little is known about the demography of succulent owl's-clover, 
although population size can fluctuate greatly from year to year. In 
the few populations where population size was reported for more than 1 
year, fluctuations up to two orders of magnitude were noted (CNDDB 
2001).
    Succulent owl's-clover is known from vernal pool habitats along the 
Southern Sierra Foothills ranging from Madera County to a disjunct 
occurrence in northern San Joaquin County. The highest density of 
occurrences of succulent owl's-clover occurs in Merced County, but the 
species is also known from Fresno, Madera, Stanislaus, and San Joaquin 
counties.
    Further discussion on succulent owl's-clover life history and 
habitat characteristics can be found in the final rule to list the 
species (62 FR 14351).

Orcuttieae Tribe

    Colusa grass, hairy Orcutt grass, Solano grass, Greene's tuctoria, 
Sacramento Valley Orcutt grass, San Joaquin Valley Orcutt grass, and 
slender Orcutt grass belong to the tribe Orcuttieae in the grass 
family, Poaceae (Reeder 1965). Many life history characteristics are 
common to all members of the Orcuttieae. All are wind pollinated, but 
pollen probably is not carried long distances between populations 
(Griggs 1980, Griggs 1981, Griggs and Jain 1983). Local seed dispersal 
is by water, which breaks up the inflorescence (Reeder 1965, Crampton 
1976, Griggs 1980, Griggs 1981). Long distance dispersal is unlikely 
(Service 1985c) but seed may have been carried occasionally by 
waterfowl (family Anatidae), tule elk (Cervus elaphus nannoides), or 
pronghorn (Antilocapra americana) in historical times (Griggs 1980). 
The seeds can remain dormant for an undetermined length of time, but at 
least for 3 or 4 years, and germinate underwater after they have been 
immersed for prolonged periods (Crampton 1976, Griggs 1980, Keeley 
1998a). Unlike typical terrestrial grasses that grow in the uplands 
surrounding vernal pools, members of the Orcuttieae flower during the 
summer months (Keeley 1998a).
    All members of the Orcuttieae tribe have large soil seed banks that 
may often be 50 times or more larger in numbers than the above ground 
population in any given year. In general, years of above average 
rainfall promote larger populations of Orcuttieae, but population 
responses vary by pool and by species (Griggs 1980, Griggs and Jain 
1983). Population sizes have been observed to vary by one to four 
orders of magnitude among successive years and to return to previous 
levels even after 3 to 5 consecutive years when no mature plants were 
present (Griggs 1980, Griggs and Jain 1983, Holland 1987). Thus, many 
years of observation are necessary to determine whether a population is 
stable or declining.
    All members of the Orcuttieae are endemic to vernal pools. Although 
the various species have been found in pools ranging widely in size, 
the vast majority occur in pools of 0.01 ha (0.03 ac) to 10 ha (24.7 
ac) (Stone et al. 1988). Larger pools retain water until May or June, 
creating optimal conditions for Orcuttieae (Crampton 1959, Crampton 
1976, Griggs 1981, Griggs and Jain 1983). Orcuttieae occur in patches 
within the pools that are essentially devoid of other plant species 
(Crampton 1959, Crampton 1976). Typically, plants near the center of a 
pool grow larger and produce more spikelets than those near the 
margins, but patterns vary depending on individual pool characteristics 
and seasonal weather conditions (Griggs 1980).
    The specific life history requirements and distribution of each of 
the seven Orcuttieae species are provided below.

Colusa Grass

    Colusa grass (Neostapfia colusana) was first described by Davy 
(1898), and given the Latin name Stapfia colusana. He had collected the 
type specimen near the town of Princeton in Colusa County. Davy soon 
realized that the name Stapfia had already been assigned to a genus of 
green algae and therefore changed the scientific name of Colusa grass 
to Neostapfia colusana (Davy 1899). Two other taxonomists proposed 
alternate Latin names for the genus in the same year, but neither is 
accepted today. No other species of Neostapfia are known (Reeder 1982, 
Reeder 1993).
    Unlike terrestrial grasses, Colusa grass has pith filled stems, 
lacks distinct leaf sheaths and ligules, and produces exudate 
(aromatic, sticky fluid discharged from the plant surface). Colusa 
grass stems and inflorescence (flower cluster) differs from other 
members of the Orcuttieae. The plant is pale green when young (Davy 
1898) but becomes brownish as the exudate darkens (Reeder 1982, Reeder 
1993).
    Existing populations of Colusa grass are concentrated northeast of 
the city of Merced in Merced County and east of Hickman in Stanislaus 
County. Colusa grass also occurs in central Merced County, in 
southeastern Yolo County, and in central Solano County (Stone et al. 
1988, Keeler-Wolf et al. 1998, CNDDB 2001). This species has been 
extirpated from Colusa County (CNDDB 2001).

[[Page 59893]]

    In the 50 years after its initial discovery (Davy 1898), Colusa 
grass was reported from only three sites other than the type locality; 
these were in Merced and Stanislaus counties. By the mid-1970's Colusa 
grass had been reported from a total of 11 sites in Colusa, Merced, 
Solano, and Stanislaus counties (Hoover 1936b, Hoover 1940, Crampton 
1959, Medeiros 1976, Reeder 1982). During the 1980's, many new 
populations of Colusa grass were located during extensive surveys. As 
of 1989, 40 occurrences were extant and 11 already had been extirpated. 
Of the 51 occurrences known up to that point, 26 were in Merced County, 
22 were in Stanislaus County, 2 were in Solano County, and one was in 
Colusa County (Stone et al. 1988, CNDDB 2001). Currently, the CNDDB 
(2001) considers 48 occurrences of Colusa grass to be ``presumed 
extant'' and 11 others as known or possibly extirpated.
    Further discussion on Colusa grass's life history and habitat 
characteristics can be found in the final rule to list the species (62 
FR 14338).

Greene's Tuctoria

    Greene's tuctoria (Tuctoria greenei) was originally assigned its 
name by Vasey (1891) as Orcuttia greenei. Greene had collected the type 
specimen in 1890 ``on moist plains of the upper Sacramento, near Chico, 
California'' (Vasey 1891), presumably in Butte County (Hoover 1941, 
Crampton 1959). Citing differences in lemma morphology, arrangement of 
the spikelets, and other differences, Reeder (1982) segregated the 
genus Tuctoria from Orcuttia and created the new scientific name 
Tuctoria greenei for this species.
    Greene's tuctoria is an erect to low growing annual with fragile 
stems that easily break apart at the nodes, which are often purplish. 
The leaves are flat and curve outward and the plants are sparsely 
hairy. The inflorescence is crowded near the tip with the lower 
spikelets more or less separated. Optimum germination of Greene's 
tuctoria seed occurs when the seed is exposed to light and anaerobic 
(lacking oxygen) conditions after stratification (Keeley 1988). 
Germination occurs several months after initial inundation (Keeley 
1998a). Tuctoria seedlings do not develop floating juvenile leaves, as 
does Orcuttia (Griggs 1980, Keeley 1998a). The adult plants apparently 
do not tolerate inundation; all five Greene's tuctoria plants in a 
Glenn County pool died when the pool refilled during late spring rains 
in 1996 (Silveira in litt. 1997). Greene's tuctoria flowers from May to 
July (Skinner and Pavlik 1994), with peak flowering in June and July 
(Griggs 1981, Broyles 1987).
    As with other vernal pool annuals, population size in Greene's 
tuctoria can vary enormously from year to year, and populations that 
have no visible plants one year can reappear in large numbers in later 
years. Population fluctuations may be due to annual variations in 
weather, particularly rainfall, to changes in management, or to a 
combination of the two. Such fluctuations were observed at scattered 
sites in Butte and Tehama counties during the 1970's (Griggs 1980, 
Griggs and Jain 1983) and at Sacramento National Wildlife Refuge, where 
the population in the single occupied pool ranged from zero to 60 
plants between 1994 and 1999 (Silveira in litt. 2000). Fluctuations of 
as much as three orders of magnitude were documented on the Vina Plains 
Preserve during the 1980's and 1990's (Alexander and Schlising 1997)
    After its discovery in Butte County in 1890, Greene's tuctoria was 
not seen again for over 40 years. During extensive surveys in the late 
1930's, Hoover (1937, 1941) found the species at sites in Fresno, 
Madera, Merced, San Joaquin, Stanislaus, Tehama, and Tulare counties. 
In fact, he described it as the most common of all Orcuttia species, 
with which it was classified at the time. By the end of the 1980's, 
Greene's tuctoria had been reported from a total of 36 occurrences in 
the same 8 counties (Stone et al. 1988, CNDDB 2001).
    Three additional occurrences of Greene's tuctoria have been 
discovered during the past decade, bringing the reported total to 39 
occurrences (Oswald and Silveira 1995, CNDDB 2001). However, 19 of the 
historical occurrences apparently have been extirpated. The other 20 
occurrences are presumed to be still in existence, although 6 of those 
have not been verified for more than a decade (Alexander and Schlising 
1997, CNDDB 2001).
    Sixty percent of the extant occurrences of Greene's tuctoria are in 
the Vina Plains area of Tehama and Butte counties. Eastern Merced 
County has about 30 percent of the known occurrences. Other occurrences 
are located in Glenn (Oswald and Silveira 1995) and Shasta counties 
(CNDDB 2001). Greene's tuctoria has been extirpated from Fresno, 
Madera, San Joaquin, Stanislaus, and Tulare counties (Stone et al. 
1988, Skinner and Pavlik 1994, CNDDB 2001).
    Further discussion on Greene's tuctoria's life history and habitat 
characteristics can be found in the final rule to list the species (62 
FR 14338).

Hairy Orcutt Grass

    Hoover (1941) described hairy Orcutt grass as (Orcuttia pilosa) 
from specimens he collected in Stanislaus County, ``12 miles east of 
Waterford'' in 1937. Hairy Orcutt grass grows in tufts consisting of 
numerous stems. The stems are decumbent (laying on the ground with the 
tip turned upward) or erect and branch from only the lower nodes. 
Almost the entire plant is pilose or hairy, giving it a grayish 
appearance. The spikelets near the tip of the inflorescence are crowded 
together, whereas those near the base are more widely spaced.
    Griggs (1974 cited in Stone et al. 1988) found that stratification 
followed by temperatures of 15 to 32[deg]C (59 to 90[deg]F) was 
necessary for seed germination in hairy Orcutt grass. Flowering period 
for the plant is mid-April through July. Seed production has not been 
studied extensively in hairy Orcutt grass, but Griggs and Jain (1983) 
did note that one individual produced more than 10,000 seeds. Although 
the predominant pollination agent for all Orcutt grasses is wind, 
native bees (Halictidae) have been observed visiting the inflorescence 
of hairy Orcutt grass to gather pollen (Griggs 1974 cited in Stone et 
al. 1988).
    Like other vernal pool annuals, the size of hairy Orcutt grass 
populations fluctuates dramatically from year to year. Population sizes 
have varied by as much as four orders of magnitude over time (Griggs 
1980, Griggs and Jain 1983, Alexander and Schlising 1997). In fact, two 
populations that had no visible plants for three successive years 
exceeded 10,000 plants in the fourth year (Griggs 1980, Griggs and Jain 
1983).
    Hairy Orcutt grass is known from sites in the southern portion of 
the Sacramento Valley and the southern Sierra foothills (Keeler-Wolf et 
al. 1998). The species has been found in Tehama, Stanislaus, Madera, 
and Merced counties (Hoover 1941, Crampton 1959, Reeder 1982, Stone et 
al. 1988, CNDDB 2001). Hairy Orcutt grass also was collected in Glenn 
County, in 1937 (CNDDB 2001); the specimen has since been lost but may 
have been misidentified as California Orcutt grass (Silveira in litt. 
2000). During the late 1980's, Stone et al. (1988) determined that 12 
historical occurrences had been extirpated but they and others 
discovered three additional populations in Madera, Stanislaus, and 
Tehama counties. One other occurrence from Madera County was previously 
considered to be hairy Orcutt grass and is listed as such in the CNDDB 
(2001); however, this population since has been

[[Page 59894]]

identified as San Joaquin Valley Orcutt grass (Stone in litt. 1992).
    Within the past decade, hairy Orcutt grass has been discovered in 
additional areas in Glenn, Madera, and Tehama counties (CNDDB 2001). 
Hairy Orcutt grass has also been discovered in another pool at the Vina 
Plains Preserve in Tehama County (Alexander and Schlising 1997). Of the 
38 element occurrences listed by the CNDDB (2001), not counting the 
misidentified population of San Joaquin Valley Orcutt grass, 24 natural 
occurrences are presumed to be still in existence. Nineteen of those 
occurrences have been confirmed as existing within the past decade 
(CNDDB 2001).
    Further discussion on hairy Orcutt grass's life history and habitat 
characteristics can be found in the final rule to list the species (62 
FR 14338).

Sacramento Orcutt Grass

    Hoover (1941) first described Sacramento Orcutt grass (Orcuttia 
viscida) as Orcuttia californica var. viscida based on the type 
specimen he collected from ``7 miles south of Folsom'' in Sacramento 
County. Reeder (1980) determined that the differences in morphology, 
seed size, and chromosome number were sufficient grounds to elevate 
Sacramento Orcutt grass to the species level as Orcuttia viscida.
    In basic form, Sacramento Orcutt grass resembles other members of 
the tribe and genus. Although all members of the Orcuttieae produce 
exudate, Sacramento Orcutt grass is particularly viscid even when 
young. The plants are densely tufted, bluish green, and covered with 
hairs. The stems are erect or spreading, 3 to 10 cm (1 to 4 in) long, 
and do not branch. The inflorescence occupies the upper one third to 
one half of the stem and consists of between 5 and 15 spikelets. The 
spikelets are closely spaced, and although distichous (arranged in two 
opposing rows) are oriented towards one side of the stem.
    Sacramento Orcutt grass flowers in May and June (Griggs 1977, 
Skinner and Pavlik 1994, Cochrane in litt. 1995a) and sets seed in June 
and July (Holland 1987). Seeds likely do not disperse far under natural 
conditions. In a 6-year period, an experimental population spread at 
most 3 m (10 ft) from the seed source, and 95 percent of plants were 
within 30 cm (12 in) of the source (Holland in litt. 1986). A 
demographic study conducted from 1974 to 1978 (Griggs 1980, Griggs and 
Jain 1983) indicated that Sacramento Orcutt grass produced an average 
of 500 seeds per plant. At one site in 1978, 88 percent of plants 
survived to maturity. The size of the seed bank stored in the soil was 
approximately 44 times as great as the population of growing plants 
(Griggs 1980, Griggs and Jain 1983). The number of plants varies with 
rainfall. Large numbers of plants grow only in years when seasonal 
rainfall exceeds 40 cm (16 in), particularly when heavy rains begin in 
November and continue through the end of April (Holland 1987). This 
species is less likely to germinate in years of below normal 
precipitation than are other members of the tribe (Griggs 1980, Griggs 
and Jain 1983).
    Sacramento Orcutt grass is endemic to the southeastern Sacramento 
Valley (Keeler-Wolf et al. 1998) and always has been restricted to 
Sacramento County. The earliest collection was from 1936 near Phoenix 
Field. Three other occurrences documented in 1941 and 1958 extended the 
range north to Orangevale and south to near Sloughhouse. Sacramento 
Orcutt grass was introduced to Phoenix Park, in Sacramento County, in 
1978. Three additional natural occurrences were discovered in the late 
1980's, including one in extreme southeastern Sacramento County near 
State Highway 104. Thus, by 1990 this species was known from a total of 
seven natural occurrences and one introduction (Stone et al. 1988, 
CNDDB 2001).
    Within the past decade, Sacramento Orcutt grass has been discovered 
at one new site in Sacramento County, within the previously known 
range. However, one entire occurrence and a portion of another have 
been extirpated. Thus, eight of the nine occurrences are still in 
existence. Five occurrences, comprising more than 70 percent of the 
occupied habitat, are concentrated into a single small area east of 
Mather Field. Two other occurrences are adjacent to each other-Phoenix 
Field Ecological Reserve and the introduced population at Phoenix Park. 
The eighth existing occurrence is near Rancho Seco Lake (Stone et al. 
1988, Cochrane in litt. 1995a, CNDDB 2001).
    Further discussion on Sacramento Orcutt grass life history and 
habitat characteristics can be found in the final rule to list the 
species (62 FR 14338).

San Joaquin Valley Orcutt Grass

    Hoover (1936b) described San Joaquin Valley Orcutt grass (Orcuttia 
inaequalis) based on a collection from ``Montpellier [sic], Stanislaus 
County.'' Hoover (1941) subsequently reduced this taxon to a variety of 
Orcuttia californica, using the combination Orcuttia californica var. 
inaequalis. Based on differences in morphology, seed size, and 
chromosome number, Reeder (1980) restored the taxon to species status.
    Mature plants of San Joaquin Valley Orcutt grass grow in tufts of 
several erect stems. The plant is grayish-green due to the long hairs 
on the stem and leaves and produces exudate. Orcuttia plants grow 
underwater for 3 months or more and have evolved specific adaptations 
for aquatic growth (Keeley 1998a).
    The earliest collection of San Joaquin Valley Orcutt grass was made 
in 1927 from the Fresno-Madera County border near Lanes Bridge (CNDDB 
2001). Hoover (1941) mentioned collections from eight sites in Fresno, 
Madera, Merced, Stanislaus, and Tulare counties. A total of 20 
occurrences had been reported by the mid 1970's, all in the same five 
counties (Crampton 1959, CNDDB 2001), but none remained as of the late 
1970's (Griggs 1980, Griggs and Jain 1983). However, since that time 
San Joaquin Valley Orcutt grass has been discovered in Merced, Madera, 
and Fresno counties, and recently additional occurrences of San Joaquin 
Valley Orcutt grass have been found, including sites in Tulare County. 
Of the 47 occurrences of San Joaquin Valley Orcutt grass reported in 
CNDDB (2001), 27 are presumed to be still in existence; 17 are 
certainly extirpated and 3 others are possibly extirpated because the 
habitat has been modified (CNDDB 2001). However, only 12 of the 
occurrences presumed still in existence have been revisited within the 
past decade, so even the most recent information is outdated. This 
species has been completely extirpated from Stanislaus County but 
remains in Fresno, Madera, Merced, and Tulare counties (Stone et al. 
1988, Skinner and Pavlik 1994, CNDDB 2001).
    Further discussion on San Joaquin Valley Orcutt grass's life 
history and habitat characteristics can be found in the final rule to 
list the species (62 FR 14338).

Slender Orcutt Grass

    Slender Orcutt grass (Orcuttia tenuis) was first named by Hitchcock 
(1934). The type specimen of slender Orcutt grass was collected in 
Goose Valley, Shasta County, in 1912. Slender Orcutt grass grows as 
single stems or in small tufts consisting of a few stems. The plants 
are sparsely hairy and branch only from the upper half of the stem. 
Although the stems typically are erect, they may become decumbent if 
many branches form near the stem tip (Reeder 1982). The inflorescence 
comprises more than half of the plant's height, and the spikelets are 
more or less evenly spaced throughout the inflorescence.
    Optimal germination of slender Orcutt grass is achieved through 
stratification

[[Page 59895]]

followed by warm days and mild nights (Griggs 1974 in Stone et al. 
1988). Peak flowering of this species typically occurs in May in the 
Central Valley (Griggs 1981, Reeder 1982) but not until June or July on 
the Modoc Plateau (Schoolcraft in litt. 2000). Unlike hairy Orcutt 
grass and Greene's tuctoria, slender Orcutt grass is not likely to die 
when pools are flooded by late spring or summer rains (Griggs 1980, 
Griggs and Jain 1983). Conversely, drought has been known to cause 100 
percent mortality (Griggs 1980, Griggs and Jain 1983).
    Similar to other vernal pool annuals, slender Orcutt grass 
populations can vary greatly in size from year to year. Fluctuations of 
up to four orders of magnitude have been documented in Lake and Shasta 
counties (Griggs 1980, Griggs and Jain 1983). At the Vina Plains 
Preserve, the single population ranged in size from 1,000 to 147,700 
individuals during the five times it was reported over a 13 year period 
(Stone et al. 1988, Alexander and Schlising 1997). However, slender 
Orcutt grass populations do not always fluctuate in size. Among five 
populations of slender Orcutt grass that Griggs tracked from 1973 to 
1979, two in the Dales area remained at the same order of magnitude for 
the entire period. None of the other five species of Orcuttieae 
included in the study remained stable for the full 7 years (Griggs 
1980, Griggs and Jain 1983).
    By the mid 1980s, slender Orcutt grass was known from only 18 
localities in Lake, Sacramento, Shasta, and Tehama counties (Reeder 
1982, Stone et al. 1988). During the late 1980s, Stone et al. (1988) 
and others (CNDDB 2001) discovered 34 additional occurrences of slender 
Orcutt grass. Slender Orcutt grass was found primarily in Tehama 
County, in the vicinity of Dales and on the Vina Plains. The species 
was also found in the Stillwater and Millville Plains of Shasta County, 
and at additional sites in Shasta, Siskiyou, Lake, and Sacramento 
counties (Griggs and Jain 1983, Stone et al. 1988, CNDDB 2001). During 
the past decade, 27 new occurrences of slender Orcutt grass have been 
reported. In addition to the counties where it was reported 
historically, slender Orcutt grass is now known from Lassen and Plumas 
counties. The extirpated occurrences of slender Orcutt grass were near 
Reading Airport and Stillwater Plains in Shasta County and additional 
possibly extirpated occurrences were near Goose Valley and Battle Creek 
in Tehama and Shasta counties.
    Further discussion on slender Orcutt grass's life history and 
habitat characteristics can be found in the final rule to list the 
species (62 FR 14338).

Solano Grass

    Solano grass (Tuctoria mucronata) was originally described under 
the name Orcuttia mucronata based on specimens collected ``12 miles due 
south of Dixon, Solano County'' (Crampton 1959, p. 108). Reeder (1982) 
transferred this species to a new genus, Tuctoria, resulting in the 
currently accepted name Tuctoria mucronata.
    Solano grass is grayish-green, pilose, and sticky. The tufted stems 
are decumbent and do not branch. The long leaves are rolled inward and 
have pointed tips. The base of the inflorescence is partially hidden by 
the uppermost leaves. As is characteristic of the genus, the spikelets 
are arranged in a spiral; the spikelets in the inflorescence of Solano 
grass are crowded together.
    Solano grass typically flowers in June and sets seed during July 
(Holland 1987). The demography of Solano grass has not been 
investigated in detail. Annual estimates or counts at Olcott Lake 
(Holland 1987, CNDDB 2001) indicated that population sizes for this 
species fluctuate dramatically from year to year, as do other members 
of the Orcuttieae. Solano grass was not observed at Olcott Lake from 
1976 through 1980, then reappeared in 1981 (Holland 1987), indicating 
that viable seeds can persist in the soil for a minimum of 5 years. 
Apparently both drought years and years of excessively high rainfall 
are unfavorable for Solano grass; the largest populations were observed 
after seasons of 45 to 60 cm (17.7 to 23.6 in) of precipitation 
(Holland 1987).
    Prior to 1985, Solano grass was known only from Olcott Lake in 
Solano County, which is believed to be the type locality (Crampton 
1959, CNDDB 2001). A second occurrence was discovered in 1985 
approximately 4 km (2.5 mi) southwest of Olcott Lake (CNDDB 2001). 
Solano grass is presumed to remain at the type locality, although only 
four individual plants have been found within the last decade, all in 
1993 (CNDDB 2001). The other Solano County site is still in existence. 
A third occurrence, comprising the largest population known, was 
discovered in 1993 on a Department of Defense (DOD) communications 
facility in Yolo County (CNDDB 2001).
    Further discussion on Solano grass's life history and habitat 
characteristics can be found in the Delta Green Ground Beetle and 
Solano Grass Recovery Plan (Service 1985c).
    The vernal pool plants are threatened by habitat loss and 
degradation due to urbanization, agricultural land conversion, off road 
vehicle use, flood control projects, highway projects, altered 
hydrology, landfill projects, and competition from weedy nonnative 
plants. The habitat of these species has been reduced and fragmented 
throughout their respective ranges as vernal pools continue to be 
eliminated. Further discussion on threats to the vernal pool plants can 
be found in the final rules to list these species (62 FR 34029, 62 FR 
14338, 57 FR 24192, 43 FR 44810) and in the criteria section of this 
proposed rule.

Previous Federal Action (Vernal Pool Crustaceans)

    Ms. Roxanne Bittman petitioned us to list Conservancy fairy shrimp, 
longhorn fairy shrimp, vernal pool fairy shrimp, and California 
linderiella (Linderiella occidentalis) as endangered species on 
November 19, 1990. Ms. Dee Warneycia petitioned us to list vernal pool 
tadpole shrimp as an endangered species on April 28, 1991. On May 8, 
1992, we published a proposed rule in the Federal Register (57 FR 
19856) to list the four fairy shrimp and vernal pool tadpole shrimp as 
endangered. On September 19, 1994, we published a final rule in the 
Federal Register (59 FR 48136) determining endangered status for 
Conservancy fairy shrimp, longhorn fairy shrimp and vernal pool tadpole 
shrimp and threatened status for vernal pool fairy shrimp. We withdrew 
the California linderiella as a species proposed for listing based on 
additional information received during the public review and comment 
period indicating that during the review period this species was more 
abundant than previously known.
    On April 17, 1995, the Building Industry Association of Superior 
California (BIAC) and Marvin L.Oates (Plaintiffs) filed a lawsuit in 
Federal District Court for the District of Columbia against Bruce 
Babbit (Secretary, Department of the Interior) et al. (Defendants) and 
Environmental Defense Center and Butte Environmental Council 
(Defendent-Intervenors) arguing that the listing of four vernal pool 
crustaceans (Conservancy fairy shrimp, longhorn fairy shrimp, vernal 
pool fairy shrimp, and vernal pool tadpole shrimp) violated the Act, 
the Administrative Procedures Act, the Fifth Amendment, the Tenth 
Amendment, and the Commerce Clause of the United States Constitution 
(Building Industry Association of Superior California, et al. v. Babbit 
et al., CIV 95-0726 PLF). On

[[Page 59896]]

July 25, 1997, the district court granted the defendant's motion for 
summary judgement on all aspects except the decision not to designate 
critical habitat. The plaintiffs later amended their complaint to drop 
the claim relating to the designation of critical habitat and the 
district court vacated its ruling regarding this matter. On April 12, 
2000, the Butte Environmental Council filed suit, alleging that our 
failure to establish critical habitat for the four vernal pool 
crustaceans violated the Endangered Species Act and the Administrative 
Procedures Act (Butte Environmental Council v. White CIV S-00-797 WES 
GGH). On February 9, 2001, the U.S. District Court for the Eastern 
District of California granted the plaintiff's motion for summary 
judgement and required the defendants, to the maximum extent prudent 
and determinable, to designate critical habitat for the four vernal 
pool crustaceans within six months.
    On July 23, 2001, the district court approved a settlement 
agreement between the parties which extended the deadline for 
designation of critical habitat to August 15, 2002. As a condition of 
the settlement, we agreed to also designate critical habitat, to the 
maximum extent prudent and determinable, for the eleven vernal pool 
plants addressed in this proposed rule by the same date.

Previous Federal Action (Vernal Pool Plants)

    Section 12 of the Act directed the Secretary of the Smithsonian 
Institution to prepare a report on plant species which were or might 
become endangered or threatened. The resulting report, dated January 9, 
1975, reviewed the status of 3,100 vascular plants. The report 
categorized as endangered six of the eleven vernal pool plants under 
consideration here, and categorized two others as threatened. The six 
plants considered endangered were hairy Orcutt grass, Sacramento Orcutt 
grass, slender Orcutt grass, Colusa grass, San Joaquin Valley Orcutt 
grass, and succulent owl's clover. The two threatened plants were 
Contra Costa goldfields and Hoover's spurge. On July 1, 1975, the 
Director of the Department of the Interior published a notice (40 FR 
27823) accepting the Smithsonian Institution's report as a listing 
petition within the context of section 4(c)(2) of the Act (petition 
provisions are now found in section 4(b)(3)), and of his intention to 
review the status of the plants covered by the report. On June 16, 
1976, based on both the Smithsonian report and on public comments and 
data pertaining to it, we published a proposed rule (41 FR 24523) to 
determine approximately 1,700 vascular plants as endangered pursuant to 
section 4 of the Act. The 1,700 plants included all eleven vernal pool 
plants considered here.
    We published a final rule to list Solano grass (along with four 
other plants) as endangered on September 28, 1978 (43 FR 44810). A 
recovery plan for Solano grass and the delta green ground beetle 
(Elaphrus viridis) was subsequently approved on September 11, 1985 
(Service 1985c). We failed to complete final listing rules for the 
other ten vernal pool plants within three years of the proposed 
listing, however, despite amendments to the Act in 1978 requiring us to 
withdraw proposed rules which were more than two years old (with a one-
year grace period). Accordingly, on December 10, 1979, we withdrew the 
proposal to list the ten remaining vernal pool plants (44 FR 70796).
    We established the remaining vernal pool plants as category 1 
candidate species in a Notice of Review (NOR) for plants published 
December 15, 1980 (45 FR 82480). Category 1 candidates were those 
species for which data in our possession was sufficient to support 
proposals to list. In a subsequent NOR published November 28, 1983 (48 
FR 53640), we downgraded the status of Contra Costa goldfields, slender 
Orcutt grass and Colusa grass to category 2. Category 2 candidates were 
defined as species for which data in our possession indicated listing 
was possibly appropriate, but for which we lacked substantial data on 
biological vulnerability and threats to support listing proposals. 
Another NOR on September 27, 1985, left the status of the remaining 
vernal pool plants unchanged (50 FR 39526).
    On February 2, 1988, we received a petition from the California 
Native Plant Society (CNPS) to emergency list Butte County meadowfoam 
as endangered. We published a 90-day administrative finding that the 
requested action might be warranted on December 30, 1988 (53 FR 53030). 
On February 15, 1991, we published a proposal to list Butte County 
meadowfoam as an endangered species (56 FR 6345), and on June 8, 1992, 
we published a final determination that Butte County meadowfoam was 
endangered (57 FR 24192).
    On February 22, 1990, we published a new NOR which re-established 
Colusa grass and Contra Costa goldfields as category 1 candidate 
species (55 FR 6184). In 1991 and 1992, we received additional 
information regarding threats to succulent owl's-clover, and so 
returned this species to category 1 status on August 5, 1993 (58 FR 
41700), in the same notice proposing to list succulent owl's clover and 
seven other vernal pool plants under the Act.
    On August 5, 1993, we published a proposal to list San Joaquin 
Valley Orcutt grass, hairy Orcutt grass, Sacramento Orcutt grass, and 
Greene's tuctoria as endangered; and to list succulent owl's-clover, 
Hoover's spurge, Colusa grass, and slender Orcutt grass as threatened 
was published on August 5, 1993 (58 FR 41700). This proposal was 
primarily based on information supplied by reports to the CNDDB, the 
Status Survey of the Grass Tribe Orcuttieae and Hoover's Spurge in the 
Central Valley of California (Stone et al. 1988), and observations by 
numerous botanists. Prior to publishing the final rule on these eight 
plants, we published another NOR on September 30, 1993 (58 FR 51144), 
indicating that the current status of the vernal pool plants as 
category 1 candidates remained unchanged. We subsequently published a 
proposal to list Contra Costa goldfields as endangered on December 19, 
1994 (59 FR 65311). Then on March 26, 1997, we published the final rule 
(62 FR 14338) for the eight plants proposed for listing in 1993. The 
final rule listed San Joaquin Valley Orcutt grass as threatened, rather 
than endangered as had originally been proposed, because we determined 
the threats to its existence to be smaller and less immediate than had 
previously been thought. All seven other plants were listed as 
proposed, resulting in a listing of hairy Orcutt grass, Sacramento 
Orcutt grass and Greene's tuctoria as endangered; and San Joaquin 
Valley Orcutt grass, succulent owl's clover, Hoover's spurge, Colusa 
grass and slender Orcutt grass as threatened. Later that same year 
(June 18, 1997) we published the final rule to list Contra Costa 
goldfields, the last of the vernal pool plants considered here, as 
endangered (62 FR 34029).
    We did not identify critical habitat in the final listing rules for 
any of the vernal pool plants or crustaceans considered here because we 
determined that the threats of increased vandalism and collection of 
listed species in the areas thus identified would make it imprudent to 
do so. Based on the interpretation of section 4 of the Act in a number 
of judicial decisions issued after the not prudent findings for these 
species were made, however, we have reconsidered those determinations 
and now consider the designation of critical habitat for the fifteen 
vernal pool species to be prudent. We are therefore proposing to 
designate critical habitat here, for the four vernal pool

[[Page 59897]]

crustaceans and eleven vernal pool plants covered by the July 23, 2001, 
court approved settlement agreement in that case.
    On August 14, 2002, we filed a motion in Butte Environmental 
Council seeking to modify the deadline of August 15, 2002, for issuance 
of final critical habitat determinations. We were unable to meet that 
deadline, and have asked the court to approve a new deadline of 
September 30, 2003.

Critical Habitat

    Critical habitat is defined in section 3(5)(A) of the Act as: (i) 
The specific areas within the geographic area occupied by a species at 
the time it is listed in accordance with the Act, on which are found 
those physical or biological features (I) essential to the conservation 
of the species and (II) that may require special management 
considerations or protection; and (ii) specific areas outside the 
geographic area occupied by a species at the time it is listed, upon a 
determination that such areas are essential for the conservation of the 
species. ``Conservation'' means the use of all methods and procedures 
that are necessary to bring an endangered or threatened species to the 
point at which listing under the Act is no longer necessary.
    Critical habitat receives protection under section 7 of the Act 
through the prohibition against destruction or adverse modification of 
critical habitat with regard to actions carried out, funded, permitted, 
or authorized by a Federal agency. Section 7 also requires conferences 
on Federal actions that are likely to result in the destruction or 
adverse modification of proposed critical habitat. Aside from the added 
protection that may be provided under section 7, the Act does not 
provide other forms of protection to lands designated as critical 
habitat. Because consultation under section 7 of the Act does not apply 
to activities on private or other non-Federal lands that do not involve 
a Federal nexus, critical habitat designation would not afford any 
additional regulatory protections under the Act.
    Critical habitat also provides non-regulatory benefits to the 
species by informing the public and private sectors of areas that are 
important for species recovery and where conservation actions would be 
most effective. Designation of critical habitat can help focus 
conservation activities for a listed species by identifying areas that 
contain the physical and biological features essential for the 
conservation of that species, and can alert the public as well as land-
managing agencies to the importance of those areas. Critical habitat 
also identifies areas that may require special management 
considerations or protection, and may help provide protection to areas 
where significant threats to the species have been identified, by 
helping people avoid causing accidental damage to such areas.
    In order to be included in a critical habitat designation, the 
habitat must first be ``essential to the conservation of the species.'' 
Critical habitat designations identify, to the extent known and using 
the best scientific and commercial data available, habitat areas that 
provide at least one of the physical or biological features essential 
to the conservation of the species (primary constituent elements, as 
defined at 50 CFR 424.12(b)). Section 3(5)(C) of the Act states that 
not all areas that can be occupied by a species should be designated as 
critical habitat unless the Secretary determines that all such areas 
are essential to the conservation of the species. Our regulations (50 
CFR 424.12(e)) also state that, ``The Secretary shall designate as 
critical habitat areas outside the geographic area presently occupied 
by the species only when a designation limited to its present range 
would be inadequate to ensure the conservation of the species.''
    Section 4(b)(2) of the Act requires that we take into consideration 
the economic impact, and any other relevant impact, of specifying any 
particular area as critical habitat. We may exclude areas from critical 
habitat designation when the benefits of exclusion outweigh the 
benefits of including the areas within critical habitat, provided the 
exclusion will not result in extinction of the species.
    Our Policy on Information Standards Under the Endangered Species 
Act, published on July 1, 1994 (59 FR 34271), provides criteria, 
establishes procedures, and provides guidance to ensure that our 
decisions represent the best scientific and commercial data available. 
It requires that our biologists, to the extent consistent with the Act 
and with the use of the best scientific and commercial data available, 
use primary and original sources of information as the basis for 
recommendations to designate critical habitat. When determining which 
areas are critical habitat, a primary source of information should be 
the listing rule for the species. Additional information may be 
obtained from a recovery plan, articles in peer-reviewed journals, 
conservation plans developed by States and surveys and studies, and 
biological assessments or other unpublished materials.
    Section 4 of the Act requires that we designate critical habitat 
based on what we know at the time of designation. Habitat is often 
dynamic, and species may move from one area to another over time. 
Furthermore, we recognize that designation of critical habitat may not 
include all of the habitat areas that may eventually be determined to 
be necessary for the recovery of the species. For these reasons, 
critical habitat designations do not signal that habitat outside the 
designation is unimportant or may not be required for recovery. Areas 
outside the critical habitat designation will continue to be subject to 
conservation actions that may be implemented under section 7(a)(1) of 
the Act and to the regulatory protections afforded by the section 
7(a)(2) jeopardy standard and the section 9 prohibitions, as determined 
on the basis of the best available information at the time of the 
action. Federally funded or assisted projects affecting listed species 
outside their designated critical habitat areas may still result in 
jeopardy findings. Similarly, critical habitat designations made on the 
basis of the best available information at the time of designation will 
not control the direction and substance of future recovery plans, HCPs, 
or other species conservation planning efforts if new information 
available to these planning efforts calls for a different outcome.
    The action of designating critical habitat does not automatically 
lead to recovery of a listed species, but it may contribute to species 
recovery. Critical habitat units are not target preserve areas: 
designation does not target and establish specific preserves and their 
boundaries. Critical habitat is designated to make Federal agencies 
aware that these areas are critical to the species. Although the 
designation of critical habitat can identify areas where a variety of 
conservation strategies may be developed to ensure the survival and 
recovery of target species, the development of these strategies are 
most appropriately taken through local planning efforts, such as the 
development of HCPs. The action of designating critical habitat does 
not result in the creation of management plans, establish numerical 
population goals, and/or prescribe specific management actions, whether 
inside or outside of such designated critical habitat. Specific 
management recommendations for areas designated as critical habitat are 
most appropriately addressed in recovery, conservation, and management 
plans, and through consultations and permits under section 7 and 
section 10 of the Act.

[[Page 59898]]

Prudency Redetermination

    Section 4(a)(3) of the Act, as amended, and implementing 
regulations (50 CFR 424.12) require that, to the maximum extent prudent 
and determinable, we designate critical habitat at the time the species 
is determined to be endangered or threatened. At the time of the final 
listing determination (62 FR 34029, 62 FR 14338, 59 FR 48136, 57 FR 
24192), we found that designation of critical habitat was not prudent 
for the vernal pool crustaceans and plants (excluding Solano grass). At 
the time of final listing of Solano grass (43 FR 44810), we did not 
make any determination about whether or not designation of critical 
habitat was prudent. Our regulations (50 CFR 424.12(a)(1)) state that 
designation of critical habitat is not prudent when one or both of the 
following situations exist--(1) The species is threatened by taking or 
other human activity, and identification of critical habitat can be 
expected to increase the degree of such threat to the species, or (2) 
such designation of critical habitat would not be beneficial to the 
species. In our final listing rules for the vernal pool crustaceans and 
plants (excluding Solano grass), we believed that publication of 
precise maps and descriptions of critical habitat for the vernal pool 
crustaceans and plants could make these species more vulnerable to 
incidents of vandalism or other human activities such as discing, 
grading, or filling (62 FR 34029, 62 FR 14338, 59 FR 48136, 57 FR 
24192). In addition, we determined that publication of precise maps and 
descriptions of critical habitat for the vernal pool plants would 
increase the vulnerability of these species to incidents of collection 
(62 FR 34029, 62 FR 14338, 57 FR 24192). Therefore, we determined that 
the designation of critical habitat would increase the degree of threat 
to the vernal pool crustaceans and plants. We also determined that 
designation of critical habitat was not beneficial for the vernal pool 
plant species (excluding Solano grass) because many populations of 
these species were found on private lands (62 FR 34029, 62 FR 14338, 57 
FR 24192). For Butte County meadowfoam and Contra Costa goldfields, we 
believed that Federal involvement in the areas where these plant 
species occurred could be identified without designation of critical 
habitat (62 FR 34029, 57 FR 24192). For eight of the vernal pool plant 
species (succulent owl's-clover, Hoover's spurge, Colusa grass, San 
Joaquin Valley Orcutt grass, hairy Orcutt grass, slender Orcutt grass, 
Sacramento Orcutt grass, and Greene's tuctoria), we believed that 
Federal agencies were aware of the species' presence and were already 
addressing conservation efforts where the species were found on Federal 
lands (62 FR 14338).
    In 1995, the CDFG received a grant from the U.S. Environmental 
Protection Agency (EPA) to map vernal pools in particular areas for 
conservation purposes (Vendlinski 2000). As a result of this effort, 
the CDFG published a report which delineated 17 vernal pool regions 
throughout California (Keeler-Wolf et al. 1998). In 1997, Robert 
Holland's original 1973-1974 map of vernal pools in the Central Valley 
was updated and the results were documented Holland (1998). In 1998, we 
published the Recovery Plan for Vernal Pools of Southern California 
(Service 1998) which outlined recovery strategies for seven vernal pool 
species (two vernal pool crustaceans and five vernal pool plants) 
including the San Diego fairy shrimp (Branchinecta sandiegonensis). The 
release of these data resulted in the widespread distribution of 
information about vernal pool habitat and its location to the public 
and to local jurisdictions for planning purposes. Since the release of 
these data, we have not documented an increase in the threats to the 
species addressed in this rule through vandalism, collection, habitat 
destruction, or other means. In contrast, we have witnessed an increase 
in public interest in the species and their conservation through survey 
efforts by species experts, scientific research, regional and local 
planning, and educational outreach. Since listing of the vernal pool 
crustaceans and plants, several vernal pool conservation planning 
efforts have been initiated by public agencies and non-government 
organizations. For example, in 1997 the Framework Agreement for the 
Interagency Vernal Pool Stewardship Initiative was signed by a number 
of Federal and State agencies; this agreement encourages coordination 
of vernal pool conservation efforts on a regional scale between the 
signatory agencies.
    Based on the lack of an increase in vandalism threats, we have 
reconsidered our evaluation of our original prudency determination. We 
have determined that the threats to the vernal pool crustaceans and 
plants and their habitat from the specific instances of habitat 
destruction we identified in the final listing rules do not outweigh 
the broader educational, regulatory, and other possible benefits that a 
designation of critical habitat would provide for these species. The 
instances of likely vandalism, though real, have been relatively 
isolated. Consequently, we conclude that designating critical habitat 
will not increase incidences of habitat vandalism above current levels 
for these species. In the absence of finding that critical habitat 
would increase threats to a species, if there are any benefits to 
critical habitat designation, then a prudent finding is warranted. The 
potential benefits include: (1) Triggering consultations under section 
7 of the Act in new areas where it would not otherwise occur because, 
for example, it is or has become unoccupied or the occupancy is in 
question; (2) focusing conservation activities on the most essential 
areas; (3) providing educational benefits to State or county 
governments or private entities; and, (4) preventing people from 
causing inadvertent harm to the species. Therefore, we conclude that 
the benefits of designating critical habitat on lands essential for the 
conservation of the vernal pool crustaceans and plants outweigh the 
risks of increased vandalism resulting from such designation. Critical 
habitat for the 4 vernal pool crustaceans and 11 vernal pool plants 
addressed herein is prudent and we are subsequently proposing critical 
habitat for them in this proposed rule.
    All of the proposed critical habitat units contain one or more of 
the primary constituent elements for the vernal pool crustaceans or 
plants addressed in this proposed rule. However, as stated earlier, 
vernal pool crustaceans and plants occur in ephemeral pools that may 
not be present throughout a given year or from year to year.
    In summary, in determining areas that are essential to conserve the 
species addressed in this proposed rule, we used the best scientific 
information available to us. The critical habitat areas described below 
constitute our best assessment of areas needed for the species' 
conservation.

Methods

    In determining critical habitat for vernal pool crustaceans and 
vernal pool plants we used the best scientific and commercial data 
available. This included data and information contained in the final 
rules listing the 15 species addressed herein, research and survey 
observations published in peer reviewed articles, the Vernal Pools of 
Southern California Final Recovery Plan (Service 1998), data collected 
for the development of HCPs, reports submitted by biologists holding 
section 10(a)(1)(A) recovery permits, data collected for the 
development of a

[[Page 59899]]

Wetland Conservation Plan in Oregon, reports and documents that are on 
file in the Service's field offices, and personal discussions with 
experts outside of the Service with extensive knowledge of vernal pool 
species and habitats.
    We utilized Geographic Information System (GIS) data derived from a 
variety of Federal, State, and local agencies, and from private 
organizations and individuals. To identify where vernal pool species 
and habitats occur we evaluated GIS data of vernal pool habitats by 
Holland (1998 and 2002), and species occurrences information from the 
CNDDB (2001). We presumed occurrences identified in CNDDB to be extant 
until we received documentation that the occurrences have been 
extirpated. We also relied on unpublished species occurrence data 
contained within our files. We produced preliminary maps using GIS 
information that plotted species occurrences and vernal pool habitats 
superimposed on SPOT imagery (CNES/SPOT Image Corporation 1993-2000). 
The use of SPOT imagery allowed us to identify landmarks such as roads, 
cities, rivers, and urban areas.
    Because the minimum mapping unit of the Holland (1998 and 2002) 
vernal pool habitat data was 16 ha (40 ac) and the resolution of the 
SPOT imagery did not allow us to identify all vernal pool habitat 
areas, we then refined unit boundaries based on additional GIS data 
layers when necessary and available, including soils information from 
the Soil Survey Geographic (SSURGO) data bases (U.S. Department of 
Agriculture (USDA) 1998-2001), and the California State Soil Geographic 
(STATSGO) data bases (USDA 1994). We used geologic information 
developed by the California Department of Mines and Geology (CDMG) 
(2000) and Liss (2001). To identify the extent of flat or gently 
sloping topography where vernal pools are found we evaluated Digital 
Elevation Models from the U.S. Geologic Survey (2000).
    We also used a number of local GIS data sets for specific areas, 
including information developed through the Riverside Multiple Species 
HCP and the Vernal Pools of Southern California Final Recovery Plan 
(Service 1998), habitat mapping for Butte County (EPA 1994), Tehama 
County (2001), Shasta County (2001) Placer County (Glazner 2001), 
Solano County (2000), Yolo County (1995), Sacramento County (1999) and 
San Joaquin County (2000) in California, and by the Rogue Valley 
Council of Governments in Oregon (Evans 2000). Other smaller scale 
mapping efforts were reviewed from Solano County Farmlands and Open 
Space (2000) and East Bay Regional Parks District (2001). The specific 
layers used and the methodology employed for each unit is described 
within the unit descriptions. To determine land ownership within each 
unit we used data from the State of California (Davis et al. 1998) and 
the U.S. Bureau of Indian Affairs in Sacramento, California (2001).

Primary Constituent Elements

    In accordance with section 3(5)(A)(i) of the Act and regulations at 
50 CFR 424.12, in determining which areas to propose as critical 
habitat, we consider those physical and biological features (primary 
constituent elements) that are essential to the conservation of the 
species and that may require special management considerations or 
protection. These features include, but are not limited to--space for 
individual and population growth, and for normal behavior; food, water, 
air, light, minerals, or other nutritional or physiological 
requirements; cover or shelter; sites for breeding, reproduction, and 
dispersal; and habitats that are protected from disturbance or are 
representative of the historic geographical and ecological 
distributions of a species.
    When considering the designation of critical habitat for vernal 
pool crustaceans, we focused on the principal biological and physical 
features that support vernal pool crustacean feeding, growth, breeding, 
reproduction, and dispersal. Vernal pool crustaceans are found only in 
ephemeral wetland habitats that contain water during the winter, when 
temperatures are suitable for cyst hatching and juvenile development. 
Individuals have never been found in riverine, marine, or other 
permanent bodies of water.
    Generally, we identified two primary constituent elements for all 
four vernal pool crustacean species addressed in this proposed rule. 
Each species has primary constituent elements that differ slightly from 
these general elements discussed in later sections of this rule. We 
determined that these proposed primary constituent elements of critical 
habitat provide for the physiological, behavioral, and ecological 
requirements of the vernal pool crustaceans.
    The first primary constituent element provides the aquatic 
environment required for cyst incubation and hatching, growth and 
maturation, reproduction, feeding, sheltering, and dispersal, and the 
appropriate periods of dessication for cyst dormancy and to eliminate 
predators such as bullfrogs, fish, and other aquatic predators that 
depend on year round inundation of wetland habitats to survive. We 
conclude this element is essential to the conservation of vernal pool 
crustaceans because these species are ecologically dependent on 
seasonal fluctuations, such as absence or presence of water during 
specific times of the year, and duration of inundation (59 FR 48136). 
They cannot persist in perennial wetlands or wetlands that are 
inundated for the majority of the year, nor can they persist without 
periodic seasonal inundation.
    The second primary constituent element is essential to maintain the 
aquatic phase of the vernal pool habitat. The entire vernal pool 
complex, including the pools, swales, and associated uplands, is 
essential to support the aquatic functions of the vernal pool habitat. 
Although the uplands are not actually occupied by vernal pool 
crustaceans, they nevertheless are essential to the conservation of 
vernal pool habitat and crustaceans because they maintain the aquatic 
phase of vernal pools and swales. Associated uplands are also essential 
to provide nutrients that form the basis of the vernal pool food chain, 
including a primary food source for the vernal pool crustaceans.
    We have used vernal pool complexes as the basis for determining 
populations of vernal pool crustaceans since the species were first 
proposed for listing. The final rule to list the four vernal pool 
crustaceans states that ``[t]he genetic characteristics of the three 
fairy shrimp and vernal pool tadpole shrimp, as well as ecological 
conditions, such as watershed contiguity, indicate that populations of 
these animals are defined by pool complexes rather than by individual 
vernal pools' (Fugate 1992, Fugate 1998, King 1996). Therefore, the 
most accurate indication of the distribution and abundance of the four 
vernal pool crustaceans is the number of inhabited vernal pool 
complexes. Individual vernal pools occupied by the four species listed 
herein are most appropriately referred to as ``subpopulations'' (59 FR 
48137). Our use of vernal pool complexes to define populations of the 
four listed crustaceans was upheld by the U.S. District Court in post-
listing challenge to the listing (Building Industry Association of 
Superior California). The July 25, 1997, decision stated: ``The Court 
finds that the plaintiffs were on notice that the FWS would consider 
vernal pool complexes as a basis for determining fairy shrimp 
populations. The Court also concludes that the use of this methodology 
was neither arbitrary nor capricious.'' The Court of Appeals

[[Page 59900]]

for the D.C. Circuit upheld the district court's decision, and the 
Supreme Court has declined to hear the case.
    In identifying specific primary constituent elements for each of 
the four vernal pool crustaceans, we expanded upon the general primary 
constituent elements described above and focused on the specific 
habitat requirements of each individual vernal pool crustacean species. 
These habitat requirements and the specific primary constituent 
elements for each vernal pool crustacean are described below.

Conservancy Fairy Shrimp Primary Constituent Elements

    The Conservancy fairy shrimp is uniquely adapted to the ephemeral 
conditions of its vernal pool habitat. Helm (1998) found that the life 
span and maturation rate of Conservancy fairy shrimp did not differ 
significantly from other fairy shrimp species under the conditions he 
observed. Helm (1998) found that Conservancy fairy shrimp reached 
maturity in an average of 46 days, and lived for as long as 154 days. 
However, aquatic invertebrate growth rates are largely controlled by 
water temperature and can vary greatly (Eriksen and Brown 1980, Helm 
1998). Eriksen and Belk (1999) observe that Conservancy fairy shrimp 
produce large cohorts of offspring, and is an ``especially hyperactive 
swimmer and filter feeder.'' Conservancy fairy shrimp have only been 
observed to produce one cohort of offspring each wet season (Eriksen 
and Belk 1999).
    Observations suggest this species is generally found in pools that 
are relatively large and turbid (King et al. 1996, Helm 1998, Eriksen 
and Belk 1999). Helm (1998) found that most Conservancy fairy shrimp 
occurrences were generally within vernal pools formed on fertile, basin 
rim soils. These pool types may be over several acres in size, and are 
often alkaline. Soil types where the species is known to occur include 
Anita, Pescadero, Riz, Solano, Edminster, San Joaquin, and Peters soil 
series.
    Conservancy fairy shrimp occur with several other vernal pool 
crustaceans, including vernal pool fairy shrimp, California 
linderiella, and vernal pool tadpole shrimp (King et al. 1996, Eriksen 
and Belk 1999, Helm 1998). In general, Conservancy fairy shrimp have 
very large populations within a given pool, and is usually the most 
abundant fairy shrimp when more than one fairy shrimp species is 
present (Helm 1998, Eriksen and Belk 1999). Conservancy fairy shrimp 
are eaten by vernal pool tadpole shrimp (Alexander and Schlising 1997), 
as well as a variety of insect and vertebrate predator species.
    When considering the designation of critical habitat for 
Conservancy fairy shrimp, we focused on the principal biological and 
physical features that support Conservancy fairy shrimp feeding and 
growth, breeding and reproduction, and dispersal. These primary 
constituent elements are found in areas that support vernal pools, 
swales, or other ephemeral ponds and depressions, and their associated 
uplands. The primary constituent elements for Conservancy fairy shrimp 
include--
    (1) Vernal pools, swales, and other ephemeral wetlands and 
depressions of appropriate sizes and depths that typically become 
inundated during winter rains and hold water for sufficient lengths of 
time necessary for Conservancy fairy shrimp incubation, reproduction, 
dispersal, feeding, and sheltering, including but not limited to large, 
playa vernal pools often on basin rim landforms and alkaline soils, but 
which are dry during the summer and do not necessarily fill with water 
every year; and
    (2) The geographic, topographic, and edaphic features that support 
aggregations or systems of hydrologically interconnected pools, swales, 
and other ephemeral wetlands and depressions within a matrix of 
surrounding uplands that together form hydrologically and ecologically 
functional units called vernal pool complexes. These features 
contribute to the filling and drying of the vernal pool, and maintain 
suitable periods of pool inundation, water quality, and soil moisture 
for vernal pool crustacean hatching, growth and reproduction, and 
dispersal, but not necessarily every year.
    All of the above described primary constituent elements do not have 
to occur simultaneously within a unit for the unit to constitute 
critical habitat for Conservancy fairy shrimp. We determined the 
primary constituent elements of critical habitat for Conservancy fairy 
shrimp based on studies on their habitat and population biology 
including but not limited to--Eng et al. 1990, Gallagher 1996, 
Alexander and Schlising 1997, Helm 1998, Eriksen and Belk 1999.

Longhorn Fairy Shrimp Primary Constituent Elements

    Longhorn fairy shrimp are known only from three general locations, 
and each of these sites contain very different types of vernal pool 
habitats. Longhorn fairy shrimp in Contra Costa and Alameda counties 
live in small, clear, sandstone outcrop pools. These sandstone pools 
have a pH near neutral, and very low alkalinity and conductivity 
(Eriksen and Belk 1999). Water temperatures in these pools have been 
measured between 10 and 18[deg]C (50 and 64[deg]F). In the other two 
locations in Merced and San Luis Obispo counties where longhorn fairy 
shrimp occur, they are found in turbid, alkaline, grassland vernal 
pools (Helm 1998, Eriksen and Belk 1999). Water temperatures in these 
grassland vernal pools tend to be warmer, between 10 and 28[deg]C (50.0 
to 82.0[deg]F). However, no experimental studies have been conducted to 
determine the specific habitat requirements of longhorn fairy shrimp, 
and until research addressing the tolerance of longhorn fairy shrimp to 
a range of temperatures and water chemistries, its potential to occur 
in other types of vernal pool habitats cannot be ruled out.
    Like other fairy shrimp, longhorn fairy shrimp are highly adapted 
to the variable conditions of vernal pool habitats. Longhorn fairy 
shrimp require a minimum of 23 days, but averaged 43 days, to reach 
maturity in artificial pools described by Helm (1998). However, Helm 
(1998) found no significant differences between the life span or 
reproductive rate of longhorn fairy shrimp and other species of fairy 
shrimp he studied.
    When considering the designation of critical habitat for longhorn 
fairy shrimp, we focused on the principal biological and physical 
features that support longhorn fairy shrimp feeding and growth, 
breeding and reproduction, and dispersal. These primary constituent 
elements are found in areas that support vernal pools, swales, or other 
ephemeral ponds and depressions and their associated uplands. The 
primary constituent elements for the longhorn fairy shrimp include--
    (1) Vernal pools, swales, and other ephemeral wetlands and 
depressions of appropriate sizes and depths that typically become 
inundated during winter rains and hold water for sufficient lengths of 
time necessary for longhorn fairy shrimp incubation, reproduction, 
dispersal, feeding, and sheltering, including but not limited to 
sandstone outcrop pools and turbid alkaline pools, but which are dry 
during the summer and do not necessarily fill with water every year; 
and
    (2) The geographic, topographic, and edaphic features that support 
aggregations or systems of hydrologically interconnected pools, swales, 
and other ephemeral wetlands and depressions within a matrix of 
surrounding uplands that together form hydrologically and ecologically

[[Page 59901]]

functional units called vernal pool complexes. These features 
contribute to the filling and drying of the vernal pool, and maintain 
suitable periods of pool inundation, water quality, and soil moisture 
for vernal pool crustacean hatching, growth and reproduction, and 
dispersal, but not necessarily every year.
    All of the above described primary constituent elements do not have 
to occur simultaneously within a unit for the unit to constitute 
critical habitat for longhorn fairy shrimp. We determined the primary 
constituent elements of critical habitat for longhorn fairy shrimp 
based on studies on their habitat and population biology including but 
not limited to-- Eng et al. 1990, Fugate 1992, Gallagher 1996, Fugate 
1998, Helm 1998, and Eriksen and Belk 1999.

Vernal Pool Fairy Shrimp Primary Constituent Elements

    Vernal pool fairy shrimp generally will not hatch until water 
temperatures drop to below 10[deg]C (50[deg]F) (Gallagher 1996, Helm 
1998). Vernal pool fairy shrimp are capable of hatching multiple times 
within a single wet season if conditions are appropriate. Helm (1998) 
observed 6 separate hatches of vernal pool fairy shrimp within a single 
wet season, and Gallagher (1996) observed 3 separate hatches of vernal 
pool fairy shrimp in vernal pools in Butte County.
    Vernal pool fairy shrimp have been documented to live for as long 
as 147 days Helm (1998), but their life cycle and longevity is 
dependant upon water temperature as well as other environmental 
factors. Vernal pool fairy shrimp can reproduce in as few as 18 days at 
optimal conditions of 20[deg]C (68[deg]F) and can complete their life 
cycle in as little as 63 days (Gallagher 1996, Helm 1998). However, 
maturation and reproduction rates of vernal pool crustaceans are 
controlled by water temperature and can vary greatly (Eriksen and Brown 
1980, Helm 1998). Helm (1998) observed that vernal pool fairy shrimp 
did not reach maturity until 41 days at water temperatures of 15[deg]C 
(59[deg]F). Vernal pool fairy shrimp have been collected at water 
temperatures as low as 4.5[deg]C (40[deg]F) (Eriksen and Belk 1999), 
however, the species has not been found in water temperatures above 
about 23[deg]C (73[deg]F) (Helm 1998, Eriksen and Belk 1999).
    Vernal pool fairy shrimp occupy a variety of different vernal pool 
habitats, from small, clear, sandstone rock pools to large, turbid, 
alkaline, grassland valley floor pools (Eng et al. 1990, Helm 1998, 
CNDDB 2001). The pool types where the species has been found include 
Northern Hardpan, Northern Claypan, Northern Volcanic Mud Flow, and 
Northern Basalt Flow vernal pools which formed on a variety of geologic 
formations and soil types (CNDDB 2001). Although vernal pool fairy 
shrimp have been collected from large vernal pools, including one 
exceeding 10 ha (25 ac) in area (Eriksen and Belk 1999), they are most 
frequently found in pools measuring less than 0.02 ha (0.05 ac) in area 
(Helm 1998, Gallagher 1996). The species occurs at elevations from 10 m 
(33 ft) to 1,220 m (4,003 ft) (Eng et al. 1990), and is typically found 
in pools with low to moderate amounts of salinity or total dissolved 
solids (Keeley 1984, Syrdahl 1993). Vernal pools are mostly rain fed, 
resulting in low nutrient levels and dramatic daily fluctuations in pH, 
dissolved oxygen, and carbon dioxide (Keeley and Zedler 1998). Although 
there are many observations of the environmental conditions where 
vernal pool fairy shrimp have been found, there have been no 
experimental studies investigating the specific habitat requirements of 
this species.
    When considering the designation of critical habitat for vernal 
pool fairy shrimp, we focused on the principal biological and physical 
features that support vernal pool fairy shrimp feeding and growth, 
breeding and reproduction, and dispersal. These primary constituent 
elements are found in areas that support vernal pools, swales, or other 
ephemeral ponds and depressions and their associated uplands. The 
primary constituent elements for vernal pool fairy shrimp include--
    (1) Vernal pools, swales, and other ephemeral wetlands and 
depressions of appropriate sizes and depths that typically become 
inundated during winter rains and hold water for sufficient lengths of 
time necessary for vernal pool fairy shrimp incubation, reproduction, 
dispersal, feeding, and sheltering, including but not limited to 
Northern Hardpan, Northern Claypan, Northern Volcanic Mud Flow, and 
Northern Basalt Flow vernal pools formed on a variety of geologic 
formations and soil types, but which are dry during the summer and do 
not necessarily fill with water every year; and
    (2) The geographic, topographic, and edaphic features that support 
aggregations or systems of hydrologically interconnected pools, swales, 
and other ephemeral wetlands and depressions within a matrix of 
surrounding uplands that together form hydrologically and ecologically 
functional units called vernal pool complexes. These features 
contribute to the filling and drying of the vernal pool, and maintain 
suitable periods of pool inundation, water quality, and soil moisture 
for vernal pool crustacean hatching, growth and reproduction, and 
dispersal, but not necessarily every year.
    All of the above described primary constituent elements do not have 
to occur simultaneously within a unit for the unit to constitute 
critical habitat for one of these species. We determined the primary 
constituent elements of critical habitat for vernal pool fairy shrimp 
based on studies on their habitat and population biology including but 
not limited to--Eng et al. 1990, Fugate 1992, Gallagher 1996, Fugate 
1998, Helm 1998, and Eriksen and Belk 1999.

Vernal Pool Tadpole Shrimp Primary Constituent Elements

    Although the vernal pool tadpole shrimp is adapted to survive in 
ephemeral vernal pool habitat, the species has a relatively long life 
span compared to other vernal pool crustaceans. Helm (1998) found that 
vernal pool tadpole shrimp lived significantly longer than any other 
species observed under the same conditions except California 
linderiella (Linderiella occidentalis). Vernal pool tadpole shrimp 
continue growing throughout their lives, periodically molting their 
shells. These shells can often be found in vernal pools where the 
species occurs. Helm (1998) found that vernal pool tadpole shrimp took 
a minimum of 25 days to mature and the mean age at first reproduction 
was 54 days. Other researchers have observed that vernal pool tadpole 
shrimp generally take between 21 to 28 days to mature (Ahl 1991, King 
1996). Ahl (1991) found that reproduction did not begin until 
individuals were larger than 10 mm (0.39 in) carapace length. Variation 
in growth and maturation rates may be a result of differences in water 
temperature, which strongly influences the growth rates of aquatic 
invertebrates.
    Vernal pool tadpole shrimp occur in a wide variety of vernal pool 
habitats (Helm 1998). They have been found in pools with water 
temperatures ranging from 10[deg]C (50[deg]F) to 29[deg]C (84[deg]F) 
and pH ranging from 6.2 to 8.5 (Syrdahl 1993, King 1996). However, 
vernal pools exhibit daily and seasonal fluctuations in pH, 
temperature, dissolved oxygen, and other water chemistry 
characteristics (Syrdahl 1993, Scholnick 1995, Keeley 1998a). 
Determining vernal pool tadpole shrimp habitat requirements is not 
possible based on anecdotal evidence, and the tolerances of this 
species to specific environmental conditions have yet to be determined. 
Although vernal pool tadpole shrimp are found on a variety of geologic

[[Page 59902]]

formations and soil types, Helm (1998) found that over 50 percent of 
vernal pool tadpole shrimp occurrences were on high terrace landforms 
and Redding and Corning soils. Platenkamp (1998) found that vernal pool 
tadpole shrimp presence differed significantly between geomorphic 
surfaces at Beale Air Force Base and the species was most likely to be 
found on Riverbank formation.
    When considering the designation of critical habitat for vernal 
pool tadpole shrimp, we focused on the principal biological and 
physical features that support vernal pool tadpole shrimp feeding and 
growth, breeding and reproduction, and dispersal. These primary 
constituent elements are found in areas that support vernal pools, 
swales, or other ephemeral ponds and depressions and their associated 
uplands. The primary constituent elements for vernal pool fairy shrimp 
include:
    (1) Vernal pools, swales, and other ephemeral wetlands and 
depressions of appropriate sizes and depths that typically become 
inundated during winter rains and hold water for sufficient lengths of 
time necessary for vernal pool tadpole shrimp incubation, reproduction, 
dispersal, feeding, and sheltering, but which are dry during the summer 
and do not necessarily fill with water every year; including but not 
limited to vernal pools on Redding and Corning soils on high terrace 
landforms, and
    (2) The geographic, topographic, and edaphic features that support 
aggregations or systems of hydrologically interconnected pools, swales, 
and other ephemeral wetlands and depressions within a matrix of 
surrounding uplands that together form hydrologically and ecologically 
functional units called vernal pool complexes. These features 
contribute to the filling and drying of the vernal pool, and maintain 
suitable periods of pool inundation, water quality, and soil moisture 
for vernal pool crustacean hatching, growth and reproduction, and 
dispersal, but not necessarily every year.
    All of the above described primary constituent elements do not have 
to occur simultaneously within a unit for the unit to constitute 
critical habitat for vernal pool tadpole shrimp. We determined the 
primary constituent elements of critical habitat for vernal pool 
tadpole shrimp based on studies on their habitat and population biology 
including but not limited to--Longhurst 1955, Lynch 1966, Ahl 1991, 
King 1996, and Helm 1998.

General Primary Constituent Elements for Vernal Pool Plants

    The primary constituent elements of critical habitat for vernal 
pool plants are those habitat components that are essential for the 
primary biological needs of germination, growth, reproduction, and 
dispersal. All of the vernal pool plants addressed in this proposed 
rule are found only in ephemeral wetlands including vernal pools and 
swales. None of these species are known to occur in permanent wetlands, 
and none are found in strictly upland areas that are never inundated.
    Generally, we identified two primary constituent elements for all 
eleven vernal pool plants addressed in this proposed rule. Each species 
has primary constituent elements that differ slightly from these 
general elements discussed in later sections of this rule. We 
determined that these proposed primary constituent elements of critical 
habitat provide for the physiological and ecological requirements of 
the vernal pool plants.
    The first primary constituent element provides the necessary soil 
moisture and aquatic environment required for seed germination, growth 
and maturation, reproduction, and dispersal, and the appropriate 
periods of dry-down for seed dormancy. Both the wet and dry phases of 
the vernal pool help to reduce competition with strictly terrestrial or 
strictly aquatic plant species. The wet phase provides the necessary 
cues for germination and growth, while the drying phase allows the 
vernal pool plants to flower and produce seeds. We conclude this 
element is essential to the conservation of the vernal pool plants 
because these species are ecologically dependent on seasonal 
fluctuations, such as absence or presence of water during specific 
times of the year, and duration of inundation and the rate of drying of 
their habitats. They cannot persist in perennial wetlands or wetlands 
that are inundated for the majority of the year, nor can they persist 
without periodic seasonal inundation.
    The second primary constituent element is essential to maintain 
both the aquatic phase and the drying phase of the vernal pool habitat. 
Although the vernal pool plants addressed in this proposed rule do not 
occur in the strictly upland areas surrounding vernal pools, they are 
dependent on these upland areas to maintain the aquatic and drying 
phases of the vernal pool. The germination of vernal pool plants is 
dependant on the timing and length of inundation of the vernal pool. 
The rate of vernal pool drying, during which vernal pool plants must 
flower and produce seeds, is also largely controlled by interactions 
between the vernal pool and the surrounding uplands (Hanes et al. 1990, 
Hanes and Stromberg 1998).
    In identifying specific primary constituent elements for each of 
the eleven vernal pool plant species addressed in this proposed rule, 
we expanded upon the general primary constituent elements described 
above to focus on the specific habitat requirements of each of the 
eleven individual species. These habitat requirements and the specific 
primary constituent elements for each species are described below.

Butte County Meadowfoam Primary Constituent Elements

    The swales and vernal pools where Butte County meadowfoam grows are 
on intermediate fan terraces (Kelley and Associates Environmental 
Sciences 1992) in annual grasslands with a mima mound topography. Large 
cobbles are present throughout the pools and swales (Jokerst 1989). 
These pools are associated with Tuscan, Redbluff, Riverbank, and 
Modesto geologic formations, and most of them occur on soils of the 
Tuscan-Anita and the Redding-Igo complexes. Anita and Igo soils are 
confined to the pools and swales. Tuscan and Redding soils are 
restricted to the mounds. Anita soils can be up to 50 cm (19.7 in) 
deep, whereas Igo soils are no more than 18 cm (7.1 in) deep; the two 
soils are underlain by iron-silica cemented and indurated hardpan, 
respectively (Kelley and Associates Environmental Sciences 1993). Butte 
County meadowfoam has been observed on Anita clay soils annually 
regardless of rainfall but appears on Igo soils only in years of above 
average rainfall (Kelley and Associates Environmental Sciences 1992a, 
Crompton 1993, Schonholtz in litt. 1995), presumably because the former 
can hold approximately twice as much moisture (Kelley and Associates 
Environmental Sciences 1993). Confirmed occurrences have been found at 
50 to 90 m (165 to 300 ft) in elevation (McNeill and Brown 1979, CNDDB 
2001).
    The primary constituent elements of critical habitat for Butte 
County meadowfoam are those habitat components that are essential for 
the primary biological needs of germination, growth, reproduction, and 
dispersal. These primary constituent elements are found in areas that 
support vernal pools, swales, or other ephemeral ponds and depressions 
and their associated uplands. The primary constituent

[[Page 59903]]

elements for Butte County meadowfoam include:
    (1) Vernal pools, swales, and other ephemeral wetlands and 
depressions of appropriate sizes and depths and the adjacent upland 
margins of these depressions that sustain Butte County meadowfoam 
germination, growth and reproduction, including but not limited to 
vernal pool swales and the margins of vernal pools on the Tuscan, 
Redbluff, Riverbank, and Modesto geologic formations underlain by 
Tuscan-Anita and Igo-Redding complex soils among others. These habitats 
typically become inundated during winter rains, but are dry during the 
summer and do not necessarily fill with water every year; and
    (2) The associated watershed(s) and hydrologic features, including 
the pool basin, swales, and surrounding uplands (which may vary in 
extent depending on pool size and depth, soil type and depth, hardpan 
or claypan type and extent, topography, and climate) that contribute to 
the filling and drying of the vernal pool or ephemeral wetland, and 
that maintain suitable periods of pool inundation, water quality, and 
soil moisture for Butte County meadowfoam germination, growth and 
reproduction, and dispersal, but not necessarily every year.
    All of the above described primary constituent elements do not have 
to occur simultaneously within a unit for the unit to constitute 
critical habitat for Butte County meadowfoam. We determined the primary 
constituent elements of critical habitat for Butte County meadowfoam 
based on studies of their habitat and population biology including but 
not limited to--Kalin-Arroyo 1973, Dole 1988, Jokerst 1989, Kelley and 
Associates Environmental Sciences 1992a, and Crompton 1993.

Contra Costa Goldfields Primary Constituent Elements

    Contra Costa goldfields typically grows in vernal pools, swales, 
moist flats, and depressions within a grassland matrix (CNDDB 2001). 
However, several historical collections were from populations growing 
in the saline-alkaline transition zone between vernal pools and tidal 
marshes on the eastern margin of the San Francisco Bay (Baye USFWS in 
litt. 2000a). The herbarium sheet for one of the San Francisco Bay 
specimens notes that the species also grew in evaporating ponds used to 
concentrate salt (Baye in litt. 2000b). The vernal pool types from 
which this species has been reported are Northern Basalt Flow, Northern 
Claypan, and Northern Volcanic Ashflow (Sawyer and Keeler-Wolf 1995). 
The landforms and geologic formations for sites where Contra Costa 
goldfields occurs have not yet been determined. Most occurrences of 
Contra Costa goldfields are at elevations of 2 to 61 m (6 to 200 ft), 
but the recently discovered Monterey County occurrences are at 122 m 
(400 ft) and one Napa County occurrence is at 445 m (1,460 ft) 
elevation (CNDDB 2001).
    The soil types that maintain these vernal pool habitats for Contra 
Costa goldfields have not yet been identified for most localities. The 
soil series from which it is known are Aiken, Antioch, Concepcion, 
Conejo, Crispin, Haire, Linne, Los Robles, Rincon, Solano, and San 
Ysidro, plus the Arnold-Santa Ynez, Hambright-rock outcrop, and Los 
Osos complexes. Soil textures, where known, are clays or loams. At 
least in Solano County and on the shores of San Francisco Bay, Contra 
Costa goldfields grows in alkaline or saline-alkaline sites (Baye in 
litt. 2000a, Baye in litt. 2000b, CNDDB 2001).
    The primary constituent elements of critical habitat for Contra 
Costa goldfields are those habitat components that are essential for 
the primary biological needs of germination, growth, reproduction, and 
dispersal. These primary constituent elements are found in areas that 
support vernal pools, swales, or other ephemeral ponds and depressions 
and their associated uplands. The primary constituent elements for 
Contra Costa goldfields include--
    (1) Vernal pools, swales, moist flats, and other ephemeral wetlands 
and depressions of appropriate sizes and depths and the adjacent upland 
margins of these depressions that sustain Contra Costa goldfields 
germination, growth and reproduction, including, but not limited to, 
vernal pools on clay soils from a variety of soils series, rock outcrop 
pools on basalt flows, and vernal pools in saline alkaline transition 
zones with tidal marsh habitats. All of these habitats typically become 
inundated during winter rains, but are dry during the summer and do not 
necessarily fill with water every year; and
    (2) The associated watershed(s) and hydrologic features, including 
the pool basin, swales, and surrounding uplands (which may vary in 
extent depending on pool size and depth, soil type and depth, hardpan 
or claypan type and extent, topography, and climate) that contribute to 
the filling and drying of the vernal pool or ephemeral wetland, and 
that maintain suitable periods of pool inundation, water quality, and 
soil moisture for Contra Costa goldfields germination, growth and 
reproduction, and dispersal, but not necessarily every year.
    All of the above described primary constituent elements do not have 
to occur simultaneously within a unit for the unit to constitute 
critical habitat for Contra Costa goldfields. We determined the primary 
constituent elements of critical habitat for Contra Costa goldfields 
based on studies on their habitat and population biology including but 
not limited to--Ornduff 1966, Ornduff 1979, Crawford and Ornduff 1989, 
Skinner and Pavlik 1994.

Hoover's Spurge Primary Constituent Elements

    Vernal pools from which Hoover's spurge has been reported are 
classified as Northern Hardpan and Northern Claypan vernal pools 
(Sawyer and Keeler-Wolf 1995). The pools supporting this species vary 
in size from 0.19 to 243 ha (0.47 to 600 ac), with a median area of 
0.58 ha (1.43 ac) (Stone et al. 1988). Many occurrences consist of 
multiple pools that vary in area and in depth, yet not all pools at a 
site support Hoover's spurge. Deeper pools apparently provide better 
habitat for this species because the duration of inundation is longer. 
This species may occur along the margins or in the deepest portions of 
the dried pool bed (Stone et al. 1988, Alexander and Schlising 1997). A 
particularly important feature of Hoover's spurge microhabitat, at 
least in the deeper pools, is that it is nearly devoid of other 
vegetation, and thus competition from other plants is reduced (Stone et 
al. 1988).
    Vernal pools supporting Hoover's spurge occur mostly on alluvial 
fans or terraces of ancient rivers or streams, with a few on the rim of 
the Central Valley basin. Hoover's spurge is found on a wide variety of 
soils, which range in texture from clay to sandy loam. Soil series from 
which it has been reported include Anita, Laniger, Lewis, Madera, 
Meikle, Riz, Tuscan, Whitney, Willows. All of these soils may not be 
equally suitable for this species, however. For example, in one Vina 
Plains pool, Hoover's spurge grew primarily in the portion that was 
underlain by Tuscan loam and was nearly absent from the portion 
underlain by Anita clay (Alexander and Schlising 1997).
    In the Sacramento Valley occupied pools are on acidic soils over 
iron-silica cemented hardpan. Most pools supporting Hoover's spurge in 
the San Joaquin Valley are on neutral to saline-alkaline soils over 
lime-silica cemented hardpan or claypan (Broyles 1987, Stone et al. 
1988, Sawyer and Keeler-Wolf 1995, CNDDB 2001). Occurrences of

[[Page 59904]]

Hoover's spurge have been reported from elevations ranging from 26 m 
(85 ft) in Glenn County to 128 m (420 ft) in Tehama County (CNDDB 
2002).
    The primary constituent elements of critical habitat for Hoover's 
spurge are those habitat components that are essential for the primary 
biological needs of germination, growth, reproduction, and dispersal. 
These primary constituent elements are found in areas that support 
vernal pools, swales, or other ephemeral ponds and depressions and 
their associated uplands. The primary constituent elements for Hoover's 
spurge include--
    (1) Vernal pools, swales, and other ephemeral wetlands and 
depressions of appropriate sizes and depths and the adjacent upland 
margins of these depressions that sustain Hoover's spurge germination, 
growth and reproduction, including but not limited to vernal pools 
formed on neutral to saline-alkaline soils over lime-silica cemented 
hardpan or claypan, or on acidic soils over iron-silica cemented 
hardpan, that typically become inundated during winter rains, but are 
dry during the summer and do not necessarily fill with water every 
year; and
    (2) The associated watershed(s) and hydrologic features, including 
the pool basin, swales, and surrounding uplands (which may vary in 
extent depending on pool size and depth, soil type and depth, hardpan 
or claypan type and extent, topography, and climate) that contribute to 
the filling and drying of the vernal pool or ephemeral wetland, and 
that maintain suitable periods of pool inundation, water quality, and 
soil moisture for Hoover's spurge germination, growth and reproduction, 
and dispersal, but not necessarily every year.
    All of the above described primary constituent elements do not have 
to occur simultaneously within a unit for the unit to constitute 
critical habitat for Hoover's spurge. We determined the primary 
constituent elements of critical habitat for Hoover's spurge based on 
studies on their habitat and population biology including but not 
limited to--Broyles 1987, Stone et al. 1988, and Alexander and 
Schlising 1997.

Succulent Owl's-Clover Primary Constituent Elements

    Succulent owl's-clover is known mostly from vernal pools occurring 
on alluvial terrace landforms. These pool types have been described as 
both Northern Claypan and Northern Hardpan vernal pools (Sawyer and 
Keeler-Wolf 1995) within annual grassland communities (CNDDB 2001). 
However, it is found on Northern Basalt Flow vernal pools on Hideaway 
soils series at one location in the San Joaquin Valley. It is known 
from both small and large pools (EIP Associates 1999). Although not all 
pools occupied by this taxon have been studied in detail, Stebbins et 
al. (1995) collected data on six occupied pools in Fresno and Madera 
counties. Some were typical ``bowl-like'' pools, whereas others were 
more similar to swales. This subspecies has been reported from pools 
with both long and short inundation periods (EIP Associates 1999) and 
from both shallow and ``abnormally deep vernal pools,'' but approximate 
depth of these pools was not given (CNDDB 2001).
    Soil series supporting succulent owl's-clover include Amador, 
Anderson, Corning, Fallbrook, Keyes, Pentz, Ramona, Redding, San 
Joaquin, Vista, and Yokohl, as well as the Pollasky-Montpellier 
complex. Soil textures at those sites range from extremely stony loam 
to loamy clay. In the proposed UC Merced campus and community area, the 
species is found primarily on Redding gravelly loam; however, Corning, 
Keyes, and Pentz soils also contain occurrences of the species (EIP 
Associates 1999). Populations of succulent owl's-clover have been 
reported from elevations of 24 m (80 ft) at the San Joaquin County site 
to 700 m (2,300 ft) at Kennedy Table in Madera County (CNDDB 2001).
    The primary constituent elements of critical habitat for succulent 
owl's-clover are those habitat components that are essential for the 
primary biological needs of germination, growth, reproduction, and 
dispersal. These primary constituent elements are found in areas that 
support vernal pools, swales, or other ephemeral ponds and depressions 
and their associated uplands. The primary constituent elements for 
succulent owl's-clover include--
    (1) Vernal pools, swales, and other ephemeral wetlands and 
depressions of appropriate sizes and depths and the adjacent upland 
margins of these depressions that sustain succulent owl's-clover 
germination, growth and reproduction, including but not limited to 
hardpan vernal pools on alluvial terraces and San Joaquin, Redding, 
Corning, Keyes, and Pentz soils series, among others, and northern 
basalt flow vernal pools on Hideaway soils series, that typically 
become inundated during winter rains, but are dry during the summer and 
do not necessarily fill with water every year; and
    (2) The associated watershed(s) and hydrologic features, including 
the pool basin, swales, and surrounding uplands (which may vary in 
extent depending on pool size and depth, soil type and depth, hardpan 
or claypan type and extent, topography, and climate) that contribute to 
the filling and drying of the vernal pool or ephemeral wetland, and 
that maintain suitable periods of pool inundation, water quality, and 
soil moisture for succulent owl's-clover germination, growth, 
reproduction, and dispersal, but not necessarily every year.
    All of the above described primary constituent elements do not have 
to occur simultaneously within a unit for the unit to constitute 
critical habitat for succulent owl's-clover. We determined the primary 
constituent elements of critical habitat for succulent owl's-clover 
based on studies of their habitat and population biology including but 
not limited to--Hoover 1968, Chuang and Heckard 1991, Chuang and 
Heckard 1993, and EIP Associates 1999.

Colusa Grass Primary Constituent Elements

    Colusa grass has the broadest ecological range among the 
Orcuttieae. It occurs on the rim of alkaline basins in the Sacramento 
and San Joaquin valleys, as well as on acidic soils of alluvial fans 
and stream terraces along the eastern margin of the San Joaquin Valley 
and into the adjacent foothills (Stone et al. 1988). Colusa grass has 
been found in Northern Claypan and Northern Hardpan vernal pool types 
(Sawyer and Keeler-Wolf 1995) within rolling grasslands (Crampton 
1959). This species typically grows in the deepest portion of the pool 
(Crampton 1959) but also may occur on the margins (Hoover 1937, Stone 
et al. 1988). Deeper pools are most likely to provide the long 
inundation period required for germination (EIP Associates 1999).
    Several soil series maintain the vernal pool habitats where Colusa 
grass is found. Solano and Yolo county sites where Colusa grass grows 
contain vernal pools formed by soils in the Pescadero series, whereas 
those in central Merced County are formed by soils in the Landlow and 
Lewis series (Silveira in litt. 2000). The eastern Merced County and 
Stanislaus County sites include vernal pool habitats formed by the Bear 
Creek, Corning, Greenfield, Keyes, Meikle, Pentz, Peters, Raynor, 
Redding, and Whitney series (Stone et al. 1988, EIP Associates 1999, 
CNDDB 2002). The type and composition of impermeable layers underlying 
occupied vernal pools also vary, ranging from claypan in the Sacramento 
Valley to lime-silica cemented hardpan in the San Joaquin Valley 
basins, to iron-silica cemented hardpan in the eastern margin of the 
San Joaquin Valley. Tuffaceous

[[Page 59905]]

alluvium underlies some eastern San Joaquin Valley pools and 
intermittent streams where Colusa grass grows (Stone et al. 1988).
    The primary constituent elements of critical habitat for Colusa 
grass are those habitat components that are essential for the primary 
biological needs of germination, growth, reproduction, and dispersal. 
These primary constituent elements are found in areas that support 
vernal pools, swales, or other ephemeral ponds and depressions and 
their associated uplands. The primary constituent elements for Colusa 
grass include--
    (1) Vernal pools, swales, and other ephemeral wetlands and 
depressions of appropriate sizes and depths and the adjacent upland 
margins of these depressions that sustain Colusa grass germination, 
growth and reproduction, and that typically become inundated during 
winter rains, including but not limited to vernal pools formed on the 
rim of alkaline basins in the Sacramento and San Joaquin valleys, as 
well as on acidic soils of alluvial fans and stream terraces along the 
eastern margin of the San Joaquin Valley and into the adjacent 
foothills. All of these pool types are dry during the summer and do not 
necessarily fill with water every year; and
    (2) The associated watershed(s) and hydrologic features, including 
the pool basin, swales, and surrounding uplands (which may vary in 
extent depending on pool size and depth, soil type and depth, hardpan 
or claypan type and extent, topography, and climate) that contribute to 
the filling and drying of the vernal pool or ephemeral wetland, and 
that maintain suitable periods of pool inundation, water quality, and 
soil moisture for Colusa grass germination, growth and reproduction, 
and dispersal, but not necessarily every year.
    All of the above described primary constituent elements do not have 
to occur simultaneously within a unit for the unit to constitute 
critical habitat for Colusa grass. We determined the primary 
constituent elements of critical habitat for Colusa grass based on 
studies on their habitat and population biology including but not 
limited to--Crampton 1976, Griggs 1980, Reeder 1982, Griggs and Jain 
1983, Keeley 1998a, and Stone et al. 1988.

Greene's Tuctoria Primary Constituent Elements

    Greene's tuctoria has been found in three types of vernal pools: 
Northern Basalt Flow, Northern Claypan, and Northern Hardpan (Sawyer 
and Keeler-Wolf 1995, Stone et al. 1988). Occupied pools are or were 
underlain by iron-silica cemented hardpan, tuffaceous alluvium, or 
claypan (Stone et al. 1988). Of pools where the species was known to be 
extant in 1987, the median size was 0.6 ha (1.5 ac), with a range of 50 
m2 (0.01 ac) to 3.4 ha (8.4 ac) (Stone et al. 1988). Stone et al. 
(1988) noted that Greene's tuctoria grew in shallower pools than other 
members of the tribe or on the shallow margins of deeper pools, but 
they did not quantify pool depth. At the Vina Plains, Greene's tuctoria 
grew in pools of ``intermediate'' size, which dried in April or early 
May of 1995 (Alexander and Schlising 1997). The Central Valley pools 
containing Greene's tuctoria are (or were) in grasslands; the Shasta 
County occurrence is surrounded by pine forest (CNDDB 2001). Occupied 
pools in the Central Valley are (or were) at elevations of 33.5 to 134 
m (110 to 440 ft) (Stone et al. 1988), whereas the Shasta County 
occurrence is at 1,067 m (3,500 ft) (CNDDB 2001).
    In Tehama and Butte counties, Greene's tuctoria grows mostly on 
Anita clay and Tuscan loam soils, with one occurrence on Tuscan stony 
clay loam. Soil types are not certain for several other occurrences in 
this region; one is on either the Rocklin or the San Joaquin series, 
and the others are unknown. The single occurrence in the central 
portion of the Central Valley, near the Glenn and Colusa county line, 
is on strongly saline-alkaline Willows clay (Silveira in litt. 2000). 
On the eastern margin of the San Joaquin Valley, Greene's tuctoria is 
known to grow on a number of different soil series including 
Archerdale, Bear Creek, Exeter, Meikle, Ramona, Raynor, Redding, and 
San Joaquin.
    The primary constituent elements of critical habitat for Greene's 
tuctoria are those habitat components that are essential for the 
primary biological needs of germination, growth, reproduction, and 
dispersal. These primary constituent elements are found in areas that 
support vernal pools, swales, or other ephemeral ponds and depressions 
and their associated uplands. The primary constituent elements for 
Greene's tuctoria include--
    (1) Vernal pools, swales, and other ephemeral wetlands and 
depressions of appropriate sizes and depths and the adjacent upland 
margins of these depressions that sustain Greene's tuctoria 
germination, growth and reproduction, including but not limited to 
Northern Claypan, Northern Hardpan and Northern Basalt flow vernal 
pools, that typically become inundated during winter rains, but are dry 
during the summer and do not necessarily fill with water every year; 
and
    (2) The associated watershed(s) and hydrologic features, including 
the pool basin, swales, and surrounding uplands (which may vary in 
extent depending on pool size and depth, soil type and depth, hardpan 
or claypan type and extent, topography, and climate) that contribute to 
the filling and drying of the vernal pool or ephemeral wetland, and 
that maintain suitable periods of pool inundation, water quality, and 
soil moisture for Greene's tuctoria germination, growth and 
reproduction, and dispersal, but not necessarily every year.
    All of the above described primary constituent elements do not have 
to occur simultaneously within a unit for the unit to constitute 
critical habitat for Greene's tuctoria. We determined the primary 
constituent elements of critical habitat for Greene's tuctoria based on 
studies on its habitat and population biology including but not limited 
to--Griggs 1980, Griggs and Jain 1983, Stone et al. 1988, Keeley 1988, 
and Alexander and Schlising 1997.

Hairy Orcutt Grass Primary Constituent Elements

    This species is found within vernal pools formed on high or low 
stream terraces and alluvial fans (Stone et al. 1988). The median size 
of occupied pools measured in the late 1980's was 1.7 ha (4.2 ac), with 
a range of 0.34 to 250 ha (0.8 to 617.5 ac) (Stone et al. 1988). At the 
Vina Plains, hairy Orcutt grass was found growing only in pools that 
held water until May, June, or July in 1995, not in those that dried in 
April (Alexander and Schlising 1997). This species is known from 
elevations of 26 m (85 ft) in Glenn County to 123 m (405 ft) in Madera 
County (CNDDB 2001).
    Hairy Orcutt grass is found on both acidic and saline-alkaline 
soils, in pools with an iron-silica cemented hardpan or claypan. In 
Tehama and Butte counties, pools supporting hairy Orcutt grass occur on 
the Anita and Tuscan soil series (Stone et al. 1988, CNDDB 2001). At 
one pool in the Vina Plains that spans both Anita clay and Tuscan loam 
soils, hairy Orcutt grass was found growing primarily on the Anita clay 
(Alexander and Schlising 1997). At the Sacramento National Wildlife 
Refuge, hairy Orcutt grass occurs on the Willows and Riz soil series 
(Silveira in litt. 2000), whereas in the Southern Sierra Foothills 
Vernal Pool Region it occurs on the Cometa, Greenfield, Hanford, 
Meikle, and Whitney soil series (Stone et al. 1988).
    The primary constituent elements of critical habitat for hairy 
Orcutt grass are those habitat components that are essential for the 
primary biological

[[Page 59906]]

needs of germination, growth, reproduction, and dispersal. These 
primary constituent elements are found in areas that support vernal 
pools, swales, or other ephemeral ponds and depressions and their 
associated uplands. The primary constituent elements for hairy Orcutt 
grass include--
    (1) Vernal pools, swales, and other ephemeral wetlands and 
depressions of appropriate sizes and depths and the adjacent upland 
margins of these depressions that sustain hairy Orcutt grass 
germination, growth and reproduction, including but not limited to 
features occurring on both acidic and saline-alkaline soils, with an 
iron-silica cemented hardpan or claypan, and that typically become 
inundated during winter rains, but are dry during the summer and do not 
necessarily fill with water every year; and
    (2) The associated watershed(s) and hydrologic features, including 
the pool basin, swales, and surrounding uplands (which may vary in 
extent depending on pool size and depth, soil type and depth, hardpan 
or claypan type and extent, topography, and climate) that contribute to 
the filling and drying of the vernal pool or ephemeral wetland, and 
that maintain suitable periods of pool inundation, water quality, and 
soil moisture for vernal pool plant germination, growth and 
reproduction, and dispersal, but not necessarily every year.
    All of the above described primary constituent elements do not have 
to occur simultaneously within a unit for the unit to constitute 
critical habitat for hairy Orcutt grass. We determined the primary 
constituent elements of critical habitat for hairy Orcutt grass based 
on studies on their habitat and population biology including but not 
limited to--Crampton 1959, Medeiros, 1976, Griggs 1980, Griggs and Jain 
1983, Stone et al. 1988, Durgarian 1995, and Alexander and Schlising 
1997.

Sacramento Orcutt Grass Primary Constituent Elements

    Sacramento Orcutt grass has been found in Northern Hardpan and 
Northern Volcanic Mudflow vernal pools (Sawyer and Keeler-Wolf 1995). 
It occurs on high terrace sites (Stone et al. 1988) at elevations of 46 
to 82 m (150 to 270 ft) (CNDDB 2001). Occupied pools occur in blue oak 
woodland and annual grassland (Crampton 1959, Griggs 1977, CNDDB 2002). 
Among occupied pools discovered prior to 1988, the median area was 0.28 
ha (0.69 ac) and ranged from 0.1 ha (0.25 ac) to 0.82 ha (2.03 ac). 
Soils underlying pools where Sacramento Orcutt grass grows are acidic 
with an iron-silica hardpan (Stone et al. 1988), and the pools contain 
numerous cobbles (Crampton 1959, Stone et al. 1988). Four of the known 
occurrences are on soils in the Redding series, two are on Red Bluff-
Redding complex soils, two are (or were) on Xerarents-urban land-San 
Joaquin complex, and one is on Corning complex soils.
    The primary constituent elements of critical habitat for Sacramento 
Orcutt grass are those habitat components that are essential for the 
primary biological needs of germination, growth, reproduction, and 
dispersal. These primary constituent elements are found in areas that 
support vernal pools, swales, or other ephemeral ponds and depressions 
and their associated uplands. The primary constituent elements for 
Sacramento Orcutt grass include--
    (1) Vernal pools, swales, and other ephemeral wetlands and 
depressions of appropriate sizes and depths and the adjacent upland 
margins of these depressions that sustain Sacramento Orcutt grass 
germination, growth and reproduction, including but not limited to 
vernal pools on high terrace landforms on acidic soils such as Red 
Bluff, Redding, and Corning soil series. These habitats typically 
become inundated during winter rains, but are dry during the summer and 
do not necessarily fill with water every year; and
    (2) The associated watershed(s) and hydrologic features, including 
the pool basin, swales, and surrounding uplands (which may vary in 
extent depending on pool size and depth, soil type and depth, hardpan 
or claypan type and extent, topography, and climate) that contribute to 
the filling and drying of the vernal pool or ephemeral wetland, and 
that maintain suitable periods of pool inundation, water quality, and 
soil moisture for Sacramento Orcutt grass germination, growth and 
reproduction, and dispersal, but not necessarily every year.
    All of the above described primary constituent elements do not have 
to occur simultaneously within a unit for the unit to constitute 
critical habitat for Sacramento Orcutt grass. We determined the primary 
constituent elements of critical habitat for Sacramento Orcutt grass 
based on studies on their habitat and population biology including but 
not limited to--Crampton 1959, Griggs 1980, Griggs and Jain 1983, 
Holland 1987, and Stone et al. 1988.

San Joaquin Valley Orcutt Grass Primary Constituent Elements

    San Joaquin Valley Orcutt grass occurs on alluvial fans, high and 
low stream terraces (Stone et al. 1988), and tabletop lava flows 
(Stebbins et al. 1995, CNDDB 2001). This species has been reported in 
Northern Claypan, Northern Hardpan, and Northern Basalt Flow vernal 
pools (Sawyer and Keeler-Wolf 1995) within rolling grassland (Crampton 
1959). Occupied pools range in surface area from 0.014 to 4.9 ha (0.05 
to 12.1 ac), with a median area of 0.62 ha (1.54 ac) (Stone et al. 
1988). San Joaquin Valley Orcutt grass has been reported from 
elevations of 30 to 755 m (100 to 2,475 ft); the highest elevation 
sites are those on the volcanic tabletops of Fresno and Madera counties 
(Stebbins et al. 1995, CNDDB 2001).
    The pools where San Joaquin Valley Orcutt grass is known to occur 
form on acidic soils that vary in texture from clay to sandy loam. Soil 
series represented include the Hideaway series on Fresno-Madera County 
volcanic tabletops, and Amador, Cometa, Corning, Greenfield, Los 
Robles, Madera, Peters, Pollasky-Montpellier complex, Raynor, Redding, 
and San Joaquin soil series elsewhere in the range. The impermeable 
layer at historical or extant occurrences included iron-silica cemented 
hardpan, tuffaceous alluvium, and basaltic rock from ancient volcanic 
flows (Stone et al. 1988, Stebbins et al. 1995, EIP Associates 1999, 
CNDDB 2001).
    The primary constituent elements of critical habitat for San 
Joaquin Valley Orcutt grass are those habitat components that are 
essential for the primary biological needs of germination, growth, 
reproduction, and dispersal. These primary constituent elements are 
found in areas that support vernal pools, swales, or other ephemeral 
ponds and depressions and their associated uplands. The primary 
constituent elements for San Joaquin Valley Orcutt grass include--
    (1) Vernal pools, swales, and other ephemeral wetlands and 
depressions of appropriate sizes and depths and the adjacent upland 
margins of these depressions that sustain San Joaquin Orcutt grass 
germination, growth and reproduction, including but not limited to 
vernal pools on alluvial fans, high and low stream terraces, and 
tabletop lava flows. These habitats typically become inundated during 
winter rains, but are dry during the summer and do not necessarily fill 
with water every year; and
    (2) The associated watershed(s) and hydrologic features, including 
the pool

[[Page 59907]]

basin, swales, and surrounding uplands (which may vary in extent 
depending on pool size and depth, soil type and depth, hardpan or 
claypan type and extent, topography, and climate) that contribute to 
the filling and drying of the vernal pool or ephemeral wetland, and 
that maintain suitable periods of pool inundation, water quality, and 
soil moisture for San Joaquin Valley Orcutt grass germination, growth 
and reproduction, and dispersal, but not necessarily every year.
    All of the above described primary constituent elements do not have 
to occur simultaneously within a unit for the unit to constitute 
critical habitat for San Joaquin Valley Orcutt grass. We determined the 
primary constituent elements of critical habitat for San Joaquin Valley 
Orcutt grass pools based on studies on their habitat and population 
biology including but not limited to--Crampton 1959, Griggs 1980, 
Griggs and Jain 1983, Stone et al. 1988, Stebbins et al. 1995, Keeley 
1998a, and EIP Associates 1999.

Slender Orcutt Grass Primary Constituent Elements

    Slender Orcutt grass is found primarily on substrates of volcanic 
origin (Crampton 1959, Corbin and Schoolcraft 1989). Vernal pools in 
which slender Orcutt grass grows are classified as Northern Volcanic 
Ashflow and Northern Volcanic Mudflow vernal pools (Sawyer and Keeler-
Wolf 1995). Impervious layers range from iron-silica hardpan to bedrock 
(Stone et al. 1988, Corbin and Schoolcraft 1989, CNDDB 2001). Among the 
populations studied by Stone and others (1988), the median area of 
pools occupied by slender Orcutt grass was 0.65 ha (1.6 ac) and ranged 
from 0.08 to 45 ha (0.2 to 111 ac). On the Modoc Plateau, occupied 
pools known as of 1989 ranged in size from 2 to 40 ha (5 to 100 ac) and 
were typically at least 30 cm (11.8 in) deep; this species was 
restricted to the deepest areas of these pools (Corbin and Schoolcraft 
1989). Slender Orcutt grass occurs through a wide range of elevations 
corresponding to its broad geographical range. The lowest reported 
elevation was 27 m (90 ft) in Sacramento County (Stone et al. 1988) and 
the highest was 1,756 m (5,761 ft) in Plumas County (Corbin in litt. 
1999).
    Soil types supporting vernal pools where slender Orcutt grass is 
known to occur are diverse, ranging from slightly to strongly acidic 
(Stone et al. 1988) and from clay to sandy, silty, or cobbly loam 
(Corbin and Schoolcraft 1989, CNDDB 2001). The soil series has not been 
reported for all slender Orcutt grass sites but the species has been 
reported on Collayomi-Aiken-Whispering complex and the Konocti-
Hambright complex soils. Modoc Plateau occurrences occur on the Gooval, 
Lasvar, Lasvar-Pitvar complex, and Nosoni soil series, whereas 
occurrences in northeastern Sacramento Valley are on the Anita, Guenon, 
Inks, Inskip, Laniger, Moda, Redding, Toomes, and Tuscan soil series. 
The Redding soil series also supports slender Orcutt grass in 
Sacramento County (Stone et al. 1988, CNDDB 2001).
    Vegetation types in which the occupied pools occur are diverse, 
ranging from grassland and oak woodland to mixed conifer forest, silver 
sagebrush (Artemisia cana) flats, and sedge meadows (Crampton 1959, 
CNDDB 2001). Associated species vary throughout the range of slender 
Orcutt grass. Although slender Orcutt grass grows in the same vernal 
pool complexes as hairy Orcutt grass in Tehama County (including the 
Vina Plains Preserve) and Sacramento Orcutt grass in Sacramento County, 
it has not been found to share any pools with either species (Stone et 
al. 1988, Cochrane in litt. 1995a, Alexander and Schlising 1997, CNDDB 
2001).
    The primary constituent elements of critical habitat for slender 
Orcutt grass are those habitat components that are essential for the 
primary biological needs of germination, growth, reproduction, and 
dispersal. These primary constituent elements are found in areas that 
support vernal pools, swales, or other ephemeral ponds and depressions 
and their associated uplands. The primary constituent elements for 
slender Orcutt grass include--
    (1) Vernal pools, swales, and other ephemeral wetlands and 
depressions of appropriate sizes and depths and the adjacent upland 
margins of these depressions that sustain slender Orcutt grass 
germination, growth and reproduction, including but not limited to 
Northern Volcanic Ashflow and Northern Volcanic Mudflow vernal pools 
(Sawyer and Keeler-Wolf 1995) with iron-silica and bedrock hardpan 
impervious layers, and that typically become inundated during winter 
rains, but are dry during the summer and do not necessarily fill with 
water every year; and
    (2) The associated watershed(s) and hydrologic features, including 
the pool basin, swales, and surrounding uplands (which may vary in 
extent depending on pool size and depth, soil type and depth, hardpan 
or claypan type and extent, topography, and climate) that contribute to 
the filling and drying of the vernal pool or ephemeral wetland, and 
that maintain suitable periods of pool inundation, water quality, and 
soil moisture for slender Orcutt grass germination, growth and 
reproduction, and dispersal, but not necessarily every year.
    All of the above described primary constituent elements do not have 
to occur simultaneously within a unit for the unit to constitute 
critical habitat for slender Orcutt grass. We determined the primary 
constituent elements of critical habitat for slender Orcutt grass based 
on studies on their habitat and population biology including but not 
limited to--Griggs 1980, Griggs 1981, Reeder 1982, Griggs and Jain 
1983, Stone et al. 1988, Corbin and Schoolcraft 1989, and Alexander and 
Schlising 1997.

Solano Grass Primary Constituent Elements

    Solano grass has been found only in the Northern Claypan type of 
vernal pool (Sawyer and Keeler-Wolf 1995) within annual grassland 
(CNDDB 2001). Pools where Solano grass occurs tend to be milky from 
suspended sediments (Holland 1987). The occupied pools in Solano County 
are more properly described as alkaline playas or intermittent lakes 
due to their large surface area (Crampton 1959), whereas those at the 
Yolo County site are ``relatively small'' (Witham in litt. 2000a). 
Soils underlying known Solano grass sites are saline-alkaline clay or 
silty clay in the Pescadero series (Crampton 1959, CNDDB 2001). Known 
occurrences are at elevations of approximately 5 to 11 m (15 to 35 ft) 
(CNDDB 2001).
    The primary constituent elements of critical habitat for Solano 
grass are those habitat components that are essential for the primary 
biological needs of germination, growth, reproduction, and dispersal. 
These primary constituent elements are found in areas that support 
vernal pools, swales, or other ephemeral ponds and depressions and 
their associated uplands. The primary constituent elements for Solano 
grass include:
    (1) Vernal pools, swales, and other ephemeral wetlands and 
depressions of appropriate sizes and depths and the adjacent upland 
margins of these depressions that sustain Solano grass germination, 
growth and reproduction, including but not limited to Northern Claypan 
vernal pools (Sawyer and Keeler-Wolf 1995) on saline-alkaline clay or 
silty clay in the Pescadero soil series that typically become inundated 
during winter rains, but are dry during the summer and do not 
necessarily fill with water every year; and

[[Page 59908]]

    (2) The associated watershed(s) and hydrologic features, including 
the pool basin, swales, and surrounding uplands (which may vary in 
extent depending on pool size and depth, soil type and depth, hardpan 
or claypan type and extent, topography, and climate) that contribute to 
the filling and drying of the vernal pool or ephemeral wetland, and 
that maintain suitable periods of pool inundation, water quality, and 
soil moisture for Solano grass germination, growth and reproduction, 
and dispersal, but not necessarily every year.
    All of the above described primary constituent elements do not have 
to occur simultaneously within a unit for the unit to constitute 
critical habitat for Solano grass. We determined the primary 
constituent elements of critical habitat for Solano grass based on 
studies on their habitat and population biology including but not 
limited to--Griggs 1980, Holland 1987, and Stone et al. 1988.

Criteria Used To Identify Critical Habitat

    In accordance with section 3(5)(A)(I) of the Act and regulations at 
50 CFR 424.12 in determining which areas to propose as critical 
habitat, we are required to base critical habitat determinations on the 
best scientific and commercial data available and to consider those 
physical and biological features that are essential to the conservation 
of the species and that may require special management considerations 
or protection. Such requirements include but are not limited to: space 
for individual and population growth, and for normal behavior; food, 
water, air, light, minerals, or other nutritional or physiological 
requirements; cover or shelter; sites for breeding, reproduction, 
rearing of offspring; and habitats that are protected from disturbance 
or are representative of the historic geographical and ecological 
distributions of a species. Our implementing regulations at 50 CFR 
424.12(e) indicate that the Secretary shall designate as critical 
habitat areas outside the geographical area presently occupied by a 
species only when a designation limited to its present range would be 
inadequate to ensure the conservation of the species.
    The primary objective in designating critical habitat is to 
identify areas that are considered essential for the conservation of 
the species, and to highlight specific areas where special management 
considerations or protections are necessary. The Act defines the term 
``conservation'' to mean ``the use of all methods and procedures which 
are necessary to bring any endangered species or threatened species to 
the point at which the measures provided pursuant to this Act are no 
longer necessary. Such methods and procedures include, but are not 
limited to, all activities associated with scientific resources 
management such as research, census, law enforcement, habitat 
acquisition and maintenance, propagation, live trapping, and 
transplantation * * * '' Section 4(f)(1) of the Act provides for the 
development and implementation of recovery plans ``for the conservation 
and survival of endangered species and threatened species,'' and 
directs that such plans incorporate ``a description of such site-
specific management actions as may be necessary to achieve the plan's 
goal for the conservation and survival of the species;'' and 
``objective, measurable criteria which, when met, would result in a 
determination * * * that the species be removed from the list.''

General Criteria

    The Service currently is preparing a draft recovery plan that will 
describe measures and actions necessary for the conservation and 
survival of the vernal pool species addressed in this proposed rule. In 
determining the size, number, and location of areas to propose as 
critical habitat we have considered the features necessary for 
conservation of each species as recommended by the vernal pool recovery 
team, other vernal pool experts, peer reviewed literature, scientific 
reports, and other information in our files. We do not, however, 
anticipate that these areas include all of the habitat areas that may 
eventually be determined to be necessary for the conservation of the 
species addressed herein. For these reasons, critical habitat 
designations do not signal that habitat outside the designation is 
unimportant or may not be required for recovery.
    The conservation of species addressed in this rule depends on 
removing and alleviating the factors that threaten them, including 
factors that led to their population decline and subsequent Federal 
listing. Most species addressed in this proposed rule are threatened by 
common factors because they occupy the same vernal pool ecosystems.
    Holland (1998) estimated that almost three-quarters of vernal pool 
habitats in the Central Valley of California had been lost by 1997. 
Loss of habitat has been even more complete in areas outside of the 
Central Valley. In the central coast area, at least 90 percent of 
historic vernal pools have been destroyed, and most remaining pools 
have been degraded (Ferren and Pritchett 1988). In southern California 
estimated loss of vernal pool habitat ranges from 95 percent to nearly 
total (Bauder 1986, 1987, Bauder and McMillan 1998). In Oregon, 60 
percent of vernal pool habitats have been destroyed, and only 18 
percent of the remaining habitats are considered intact (Oregon Natural 
Heritage Program 1997, Borgias and Patterson 1999). As a result of 
widespread habitat loss, most of the species addressed in this rule are 
now limited to a fraction of their former ranges.
    Beginning around the mid-1800s, vernal pool habitats were destroyed 
as a result of conversion to agriculture and water diversion and 
impoundment projects (Frayer et al. 1989, Holland 1998, Kreissman 
1991). In more recent years, vernal pool habitats have been lost 
primarily as a result of widespread urbanization (Bauder 1986, Bauder 
and McMillan 1998). Much of the loss of habitat was the result of 
residential, commercial, and industrial development projects. The 
construction of infrastructures associated with urbanization has also 
contributed greatly to loss of vernal pool habitats, including the 
construction of highways, wastewater treatment plants, sewer lines, 
water supply projects, and other utility projects associated with 
urbanization in California.
    In some areas, conversion of vernal pool habitats to intensive 
agricultural uses continues to contribute to the decline of vernal pool 
habitats and the species that inhabit them. From 1992 to 1998, 50,825 
ha (125,591 ac) of grazing land were converted to other agricultural 
uses in the Central Valley of California (California Department of 
Conservation 2001). It is likely that much of this land supported 
vernal pools. Holland estimated that more than 12,950 ha (32,000 ac) of 
vernal pool habitats had been lost in the San Joaquin valley vernal 
pool region from the late 1980s until 1997, mostly as a result of 
agricultural conversion (Holland 1998). Through consultation under 
section 7 of the Act, we reviewed projects converting more than 6,070 
ha (15,000 ac) of vernal pool habitats to intensive agricultural uses.
    Vernal pool species are also threatened by other activities that 
indirectly destroy vernal pool ecosystems and render them unsuitable 
for vernal pool species, including activities that alter hydrology, 
introduce contaminants, cause erosion or sedimentation, and introduce 
non-native species into vernal pool ecosystems. Maintaining habitat 
integrity was identified by the vernal pool recovery team as an 
important consideration in planning recovery strategies for the species 
addressed in

[[Page 59909]]

this proposed rule (Vernal Pool Recovery Team in litt. 1996). The 
recovery of the species addressed in this proposed rule will depend on 
the development of recovery strategies that eliminate or minimize these 
threats so that populations can stabilize, and future declines will be 
minimized.
    Alteration of vernal pool hydrology can dramatically degrade vernal 
pool habitats. Vernal pool hydrology can be altered by a variety of 
activities, including the construction of roads, trails, ditches, or 
canals that can block the flow of water into, or drain water away from, 
vernal pools and vernal pool complexes (CNDDB 2001). Runoff from 
irrigated agricultural lands, storm water drains, or developed areas 
covered with concrete, asphalt, or irrigated lawns can dramatically 
alter the hydrology of adjacent vernal pools (Bauder 1987, Clark et al. 
1998). As described in the primary constituent element section of this 
rule, all of the species addressed herein depend on specific timing and 
duration of inundation to complete their life cycles. Altered vernal 
pool hydrology can harm vernal pool species by preventing germination 
or hatching, preventing growth and maturation, and by preventing 
reproduction and disrupting gene flow and dispersal. Altered hydrology 
can also allow invasion of habitats and extirpation of vernal pool 
species by dominant upland or aquatic species.
    Vernal pool species have also declined as a result of water 
contamination. Vernal pool crustaceans, in particular are highly 
sensitive to the water chemistry of their vernal pool habitats, and 
contamination of vernal pools may injure or kill them (Belk 1977, Eng 
et al. 1990, Gonzalez et al. 1996). Toxic chemicals, such as petroleum 
products, pesticides, herbicides, adjuvants, fertilizers, and soap may 
wash into vernal pools during development of adjacent areas. Vernal 
pools adjacent to existing developments may also be contaminated from 
roadway contaminants in surface runoff (e.g., grease, oil, and heavy 
metals). Contamination may result from discharge of fertilizers and 
pesticides into surface waters from golf courses, irrigated 
agricultural lands, or landscaped residential areas (Petrovic 1990). In 
addition to altered hydrology and contamination, vernal pool species 
have declined as a result of a variety of other incompatible land uses 
including off road vehicle use, dumping, vandalism, erosion and 
sedimentation (Service 1994c, CNDDB 2001).
    Additional threats to vernal pool species include the negative 
effects of fragmentation and isolation on populations that were once 
part of larger interconnected habitats, and the effects of small 
population sizes and loss of genetic diversity that result from habitat 
fragmentation. Fragmentation threatens the elimination of some 
populations with unforeseen natural and anthropogenic catastrophic 
events. Vernal pool species in these small habitat patches are also 
vulnerable to random fluctuations in habitat availability due to annual 
weather patterns and other environmental factors. They are also more 
vulnerable to extirpation from random fluctuations in demographic 
factors, such as birth rates and death rates (Lesica and Allendorf 
1995).
    Fragmentation of vernal pool complexes could contribute 
significantly to the loss of genetic diversity among vernal pool 
species and reduce the likelihood of recolonization events following 
population extinction by limiting opportunities for dispersal (King 
1996, Fugate 1998). The fragmentation of vernal pool habitats may 
decrease the ability of avian species to move between remaining patches 
of vernal pool habitats (Silveira 1998), which would contribute to the 
isolation of vernal pool crustacean populations by reducing cyst 
dispersal between remaining vernal pool habitat patches (Proctor 1964, 
Krapu 1974, Swanson 1974, Driver 1981, Ahl 1991). Fragmentation of 
vernal pool areas could reduce the availability of habitat for 
pollinator species, and decrease or eliminate seed production of many 
vernal pool plants (Thorp and Leong 1998).
    As described in the Primary Constituent Element section of this 
proposed rule, the conservation of the wetted area of the vernal pool 
alone is not sufficient to provide the hydrologic conditions necessary 
for the reproduction, feeding, sheltering, and dispersal of the vernal 
pool species addressed in this proposed rule. To maintain the integrity 
of the vernal pool habitat and prevent extirpation of vernal pool 
species resulting from altered hydrology, contamination, sedimentation, 
and other factors which originate in the uplands surrounding the vernal 
pools it is equally necessary to conserve the surrounding micro-
watershed and associated uplands that directly surround and feed the 
wetted area of the vernal pool or pool complex.
    The boundaries of vernal pool complexes, including vernal pools, 
swales, and the associated uplands, where vernal pool species are known 
to occur in California have been mapped by Holland (1998, 2002) and by 
a number of local and state organizations throughout California and in 
Oregon. The soil types and geologic formations which support vernal 
pools have also been mapped, and the associated landforms have been 
identified. We utilized these boundaries to identify areas that support 
vernal pools, swales, and the associated uplands that comprise the 
hydrological unit of the vernal pool complex necessary for vernal pool 
crustacean growth, reproduction, feeding, and dispersal and vernal pool 
plant germination, growth, and reproduction. We relied on these mapped 
boundaries to identify vernal pool complexes as intact, hydrologically 
functioning units. We did not dissect or fragment existing complexes 
within this designation. However, we do not believe the entire 
watershed of vernal pool habitats, as depicted by CALWATER or other 
watershed mapping efforts, is essential to the conservation of the 
species, and we are not proposing to designate entire watersheds as 
critical habitat.
    Maintaining the range of habitat types in which a species is known 
to occur has been identified as an important element in species 
recovery (Vernal Pool Recovery Team in litt. 1996). Protecting 
environmental variability will reduce the chance of losing populations 
that are important for their genetic uniqueness and adaptation to local 
environmental conditions (Fugate 1992, King 1996, Linhart and Grant 
1996, Fugate 1998). Environmental factors such as hydrology, soil 
composition and chemistry, pool size, and water chemistry, play a major 
role in determining species presence and composition in vernal pool 
plants (Holland and Griggs 1976, Holland and Dains 1990, Jokerst 1990, 
Stallings and Warren 1996). The presence and species composition of 
vernal pool crustaceans is also largely determined by physical factors 
such as pool size, depth, area, and water chemistry (Eng et al. 1990, 
Gonzales et al. 1996, Hathaway and Simovich 1996, Simovich and Hathaway 
1997, Platenkamp 1998, Simovich 1998, Helm 1998). Variation in these 
factors contributes to the wide range of life history strategies 
observed in vernal pool crustaceans and plants, and to the high levels 
of species diversity observed in vernal pool ecosystems in general. 
Various efforts to classify vernal pools, including Sawyer and Keeler-
Wolf 1995, Keeler-Wolf et al. 1998, Smith and Verrill 1998, have 
identified the locations and distributions of these different pool 
types. We consulted these sources of information to ensure we have 
accurately identified the range of

[[Page 59910]]

habitats in which each of the 15 species addressed in this proposed 
rule are known to occur.

Special Management Considerations

    In proposing critical habitat, we also have considered how this 
designation highlights habitat that needs special management 
considerations or protection. For example, we have many regional HCPs 
under development, and this designation will be useful in helping 
applicants determine what vernal pool habitat areas should be highest 
priority for special management or protection, and where there may be 
more flexibility in conservation options. This designation will guide 
them and us in ensuring that all local habitat conservation planning 
efforts are consistent with conservation objectives for these species.
    Once a vernal pool habitat has been protected from direct filling, 
it is still necessary to ensure that the habitat is not rendered 
unsuitable for vernal pool species because of factors such as altered 
hydrology, contamination, non-native species invasions, or other 
incompatible land uses. Even the best designed vernal pool preserve may 
still be susceptible to alterations that render it unsuitable for 
vernal pool species. Many of the factors that cause the decline and 
extirpation of vernal pool species can be controlled through special 
management actions. Examples of special management actions that may be 
necessary to prevent further declines and loss of populations of 
species addressed in this rule include--
    (1) Actions to prevent or reduce competition of vernal pool plants 
with invasive species. Many of the species addressed in this rule are 
threatened by invasion of non-native species (CNDDB 2001). Special 
management actions can be taken to reduce the negative effects of such 
invasions. For example, grazing can be effectively used to control a 
variety of upland exotic plants. However, the timing and intensity of 
grazing is critical to its success as a management tool, and these 
factors should be closely monitored. Alternatively, inappropriate 
grazing can also pose a threat to many of the vernal pool plant species 
(CNDDB 2001). Prescribed burning is another management tool that may be 
effective in controlling non-native plant species (Pollack and Kan 
1998). Fire must also be appropriately timed and fire frequency is 
important. The potential for alteration of nutrient cycling must be 
also considered. Other management techniques for control of invasive 
species include mowing, hand removal, and selective herbicide 
applications. Any technique employed must be carefully controlled and 
monitored to ensure that it does not negatively affect the vernal pool 
species.
    (2) Actions to restore vernal pool hydrology. Alteration of natural 
hydrology threatens many of the species addressed in this proposed rule 
(CNDDB 2001). In many cases other threats, such as the invasion of non-
native species or contamination, are facilitated by alterations of 
natural vernal pool hydrology. Special management actions, such as the 
removal of dams or other structures which artificially increase the 
length of vernal pool inundation, the removal of ditches that 
artificially drain vernal pools, or the construction of berms or 
reconstruction of culverts to prevent water from flowing artificially 
into vernal pools from adjacent areas, can be taken to restore natural 
vernal pool hydrology. Modification of grazing regimes may also restore 
natural vernal pool hydrology (Barry 1998). Monitoring of vernal pool 
hydrology is important to ensure that restoration actions are 
successful.
    (3) Actions to reduce human degradation of vernal pools. Special 
management actions such as fencing, trail building, and posting signs 
can help to reduce human activities that threaten vernal pool species. 
These actions may reduce the damage resulting from off-road vehicle 
use, dumping, and vandalism that threatens many of the species 
addressed in this proposed rule.
    (4) Actions to restore severely degraded habitats. Active 
restoration of highly degraded vernal habitats may be necessary in some 
areas. Such restoration may involve earth moving activities designed to 
restore historic pool and swale topography and to reestablish natural 
vernal pool hydrology (e.g., Ferren and Hubbard 1998, Black and Zedler 
1998). These types of actions are extremely complex, and require 
diligent planning and monitoring to ensure their success. Active 
restoration is only recommended for seriously degraded habitats that 
otherwise would not maintain natural vernal pool ecosystem processes.

Summary of Proposed Designation

    Table 1 shows approximate areas of proposed critical habitat, by 
unit and species. Because of overlap between units established for 
different species, the total of all critical habitat proposed is much 
less than the sum of critical habitat areas proposed for each species. 
Lands proposed are under private, State, and Federal ownership and 
divided into 128 Critical Habitat Units. The table provides separate 
columns for privately owned land subject to conservation easements or 
agreements and other privately owned lands.

              Table 1.--Approximate Areas of Proposed Critical Habitat for the Vernal Pool Crustaceans and Plants in California and Oregon
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                  Federal           State and local           Private           Private (other)            Total
                                          --------------------------------------------    (conservation)    --------------------------------------------
          Critical habitat units                                                      ----------------------
                                            Hectares    Acres     Hectares    Acres     Hectares    Acres     Hectares    Acres     Hectares     Acres
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                Conservancy Fairy Shrimp
--------------------------------------------------------------------------------------------------------------------------------------------------------
1........................................          0          0          0          0      6,747     16,672     13,799     34,097     20,546      50,769
2........................................      5,187     12,816          0          0          0          0        531      1,313      5,718      14,129
3........................................        241        596        329        814      1,072      2,648      8,285     20,471      9,927      24,529
4........................................          0          0          0          0          0          0        603      1,490        603       1,490
5........................................        299        739          0          0          0          0          3          7        302         746
6........................................        427      1,056         11         26      4,566     11,283     58,746    145,160     63,750     157,525
7........................................     12,765     31,542      3,096      7,649      1,119      2,765     29,163     72,060     46,142     114,016
8........................................     18,042     44,581          0          0          0          0        789      1,950     18,831      46,531
                                          ------------
    Species Total........................     36,961     91,330      3,435      8,489     13,504     33,368    111,919    276,548    165,820     409,735
------------------------------------------
                                                                  Longhorn Fairy Shrimp
--------------------------------------------------------------------------------------------------------------------------------------------------------
1 A-B....................................          0          0          0          0          0          0        321        794        321         794

[[Page 59911]]


2........................................      9,413     23,258      3,096      7,651      1,119      2,765     16,189     40,003     29,817      73,677
3........................................      6,293     15,549         94        233          0          0      4,079     10,080     10,466      25,862
                                          ------------
    Species Total........................     15,705     38,807      3,191      7,884      1,119      2,765     20,590     50,877     40,605     100,333
------------------------------------------
                                                                Vernal Pool Fairy Shrimp
--------------------------------------------------------------------------------------------------------------------------------------------------------
1 A-G....................................          0          0          0          0          0          0        862      2,130        862       2,130
2 A-E....................................          0          0          0          0          0          0        911      2,251        911       2,251
3 A-C....................................          0          0          0          0          0          0        931      2,301        931       2,301
4 A-B....................................        175        432          0          0          0          0        186        460        361         892
5........................................         17         42          0          0         53        130      1,779      4,397      1,849       4,569
6........................................          0          0        175        433          0          0     18,386     45,432     18,562      45,865
7........................................          0          0          0          0      6,747     16,672     17,136     42,343     23,883      59,015
8........................................          0          0          0          0          0          0      5,760     14,233      5,760      14,233
9........................................         76        187          0          0          7         17      1,374      3,394      1,456       3,598
10.......................................      5,187     12,816          0          0          0          0        531      1,313      5,718      14,129
11.......................................      2,035      5,028          0          0          0          0        818      2,021      2,853       7,049
12.......................................          0          0          0          0         64        157     19,324     47,748     19,387      47,905
13.......................................          6         16          0          0          0          0     14,859     36,717     14,866      36,733
14.......................................          0          0        630      1,557      4,014      9,918     21,956     54,253     26,600      65,728
15.......................................          0          0         60        149          0          0      1,563      3,863      1,624       4,012
16.......................................      1,015      2,507      1,038      2,564      1,137      2,809     31,721     78,381     34,910      86,261
17.......................................          0          0        170        420          0          0        486      1,201        656       1,621
18.......................................          0          0          0          0          0          0      7,105      17,55     77,105      17,557
19 A-C...................................          0          0         64        157        288        711      3,004      7,424      3,356       8,292
20.......................................        299        739          0          0          0          0          3          7        302         746
21.......................................          7         17         25         61          0          0     25,285     62,479     25,317      62,557
22.......................................          3          8         11         26      3,464      8,559     40,628    100,391     44,106     108,984
23.......................................     13,943     34,452      3,096      7,649      1,119      2,765     37,753     93,287     55,911     138,153
24 A-B...................................          0          0          0          1          0          0     17,231     42,578     17,232      42,579
25.......................................         65        161          0          0          0          0        929      2,295        994       2,456
26 A-C...................................          0          0        348        861          0          0      2,845      7,030      3,193       7,891
27 A-B...................................      2,742      6,776        490      1,210      1,325      3,274      3,285      8,117      7,842      19,377
28.......................................      1,581      3,906          2          5          0          0     46,542    115,004     48,125     118,915
29 A-C...................................     20,586     50,868          0          0          0          0     20,468     50,576     41,054     101,444
30.......................................      6,293     15,549         94        233          0          0      4,079     10,080     10,466      25,862
31.......................................      2,236      5,526          0          0          0          0      6,163     15,228      8,399      20,754
32.......................................     18,042     44,580          0          0          0          0        790      1,951     18,831      46,531
33 A-C...................................          0          0          0          0          0          0      2,319      5,730      2,319       5,730
34.......................................          0          0        761      1,880        830      2,052        127        314      1,718       4,246
35.......................................          0          0          0          0          0          0         97        239         97         239
                                          ------------
    Species Total........................     74,307    183,610      6,963     17,206     19,047     47,064    357,239    882,725    457,556   1,130,605
------------------------------------------
                                                               Vernal Pool Tadpole Shrimp
--------------------------------------------------------------------------------------------------------------------------------------------------------
1........................................         17         42          0          0         53        130      1,779      4,397      1,849       4,569
2........................................      6,226     15,383        437      1,081      6,320     15,617      7,463     18,441     20,446      50,522
3........................................          0          0          0          0      6,747     16,672     17,136     42,343     23,883     359,015
4........................................        127        313          0          0         84        208     15,764     38,953     15,975      39,474
5........................................      5,187     12,816          0          0          0          0        531      1,313      5,718      14,129
6........................................          0          0          0          0          0          0        526      1,299        526       1,299
7........................................      2,035      5,028          0          0          0          0        818      2,021      2,853       7,049
8........................................          6         16          0          0          0          0     14,859     36,717     14,866      36,733
9........................................          0          0        630      1,557      4,039      9,981     24,393     60,275     29,063      71,813
10.......................................        130        321          0          0          0          0         62        153        192         474
11.......................................        760      1,879      1,038      2,565      1,136      2,808     31,675     78,269     34,610      85,521
12.......................................          0          0          0          0          0          0        603      1,490        603       1,490
13.......................................          0          0          0          0          0          0      9,408     23,246      9,408      23,246
14.......................................         10         24          0          0          0          0        448      1,108        458       1,132
15.......................................          3          8         11         26      4,566     11,283     66,496    164,309     71,076     175,626
16.......................................     13,943     34,452      3,096      7,649      1,119      2,765     37,753     93,287     55,911     138,153
17.......................................         85        209        174        430        259        639        223        551        740       1,829
18.......................................          0          0        348        861          0          0      2,845      7,030      3,193       7,891
                                          ------------
    Species Total........................     28,528     70,491      5,734     14,169     24,324     60,103    232,784    575,202    291,370     719,965
------------------------------------------

[[Page 59912]]


                                                                 Butte County Meadowfoam
--------------------------------------------------------------------------------------------------------------------------------------------------------
1........................................          0          0          0          0          0          0      6,105     15,086      6,105      15,086
2........................................          0          0          0          0          0          0      3,508      8,667      3,508       8,667
3........................................          9         22          0          0          0          0      1,687      4,169      1,696       4,191
4........................................          0          0          0          0          0          0      5,011     12,382      5,011      12,382
                                          ------------
    Species Total........................          9         22          0          0          0          0     16,311     40,304     16,320      40,326
------------------------------------------
                                                                      Colusa Grass
--------------------------------------------------------------------------------------------------------------------------------------------------------
1........................................        130        322          0          0          0          0         62        152        192         474
2........................................         94        233        258        637      1,137      2,809      5,664     13,996      7,153      17,675
3........................................          0          0          0          0          0          0     16,475     40,709     16,475      40,709
4........................................          0          0          0          0          1          2     35,133     86,812     35,134      86,814
5........................................          0          0         25         61          0          0     19,825     48,988     19,850      49,049
6........................................        427      1,055         11         26          0          0     45,204    111,698     45,642     112,779
7 A-B....................................      1,422      3,514          0          0          0          0      6,741     16,656      8,163      20,170
                                          ------------
    Species Total........................      2,074      5,124        293        724      1,138      2,811    129,104    319,011    132,608     327,670
------------------------------------------
                                                                 Contra Costa Goldfields
--------------------------------------------------------------------------------------------------------------------------------------------------------
1........................................          0          0          0          0          0          0      1,067      2,637      1,067       2,637
2........................................          0          0          0          0          0          0        411      1,016        411       1,016
3........................................          0          0          0          0          0          0        274        678        274         678
4........................................      1,954      4,828        122        301          0          0      5,809     14,355      7,885      19,484
5 A-B....................................          0          0          0          0          0          0        410      1,014        410       1,014
6........................................          0          0          0          0          0          0        242        599        242         599
7........................................          0          0        291        718          0          0      1,088      2,688      1,378       3,406
8........................................        448      1,108          0          0          0          0         10         24        458       1,132
9........................................      3,370      8,326          2          4          0          0          0          1      3,372       8,331
                                          ------------
    Species Total........................      5,772     14,262        414      1,023          0          0      9,313     23,012     15,499      38,297
------------------------------------------
                                                                    Greene's Tuctoria
--------------------------------------------------------------------------------------------------------------------------------------------------------
1........................................        903      2,231          0          0          0          0         70        172        972       2,403
2........................................          0          0          0          1      7,096     17,534      4,577     11,310     11,674      28,845
3........................................          0          0          0          0          0          0        979      2,418        979       2,418
4........................................          0          0          0          0          4          9        295        729        299         738
5........................................      5,187     12,816          0          0          0          0        531      1,313      5,718      14,129
6........................................          0          0          0          0          1          2     36,413     89,976     36,414      89,978
7........................................        427      1,056         11         26      4,566     11,283     68,703    169,762     73,707     182,127
8........................................          0          0          0          0          0          0     13,222     32,670     13,222      32,670
                                          ------------
    Species Total........................      6,517     16,103         11         27     11,667     28,828    124,789    308,350    142,984     353,308
------------------------------------------
                                                                   Hairy Orcutt Grass
--------------------------------------------------------------------------------------------------------------------------------------------------------
1........................................          0          0          0          0      6,219     15,366      2,530      6,251      8,748      21,617
2........................................          0          0          0          0          0          0        979      2,418        979       2,418
3........................................      5,187     12,816          0          0          0          0        531      1,313      5,718      14,129
4........................................          7         17         25         61          0          0     25,286     62,482     25,318      62,560
5........................................          0          0          0          0          0          0      9,085     22,448      9,085      22,448
6........................................          0          0          4         10          0          0     15,820     39,090     15,824      39,100
                                          ------------
    Species Total........................      5,194     12,833         29         71      6,219     15,366     54,231    134,002     65,671     162,272
------------------------------------------
                                                                     Hoover's Spurge
--------------------------------------------------------------------------------------------------------------------------------------------------------
1........................................          0          0          0          1      7,096     17,534      4,577     11,310     11,674      28,845
2........................................          0          0          0          0          0          0        979      2,418        979       2,418
3........................................      5,187     12,816          0          0          0          0        531      1,313      5,718      14,129
4........................................          0          0          0          0          1          2     16,838     41,607     16,839      41,609
5........................................          0          0         24         60          0          0     19,826     48,989     19,850      49,049
6........................................      3,232      7,985          0          0          0          0     11,078     27,374     14,310      35,359
7 A-D....................................         13         33        355        877          0          0     12,007     29,668     12,375      30,578
                                          ------------

[[Page 59913]]


    Species Total........................      8,432     20,834        380        938      7,097     17,536     65,836    162,679     81,744     201,987
------------------------------------------
                                                                 Sacramento Orcutt Grass
--------------------------------------------------------------------------------------------------------------------------------------------------------
1........................................          0          0          3          7          0          0         26         65         29          72
2........................................          0          0          0          0          0          0      8,853     21,875      8,853      21,875
3........................................          0          0        247        610      3,135      7,747     12,368     30,561     15,750      38,918
                                          ------------
    Species Total........................          0          0        250        617      3,135      7,747     21,247     52,501     24,632      60,865
------------------------------------------
                                                             San Joaquin Valley Orcutt Grass
--------------------------------------------------------------------------------------------------------------------------------------------------------
1........................................        427      1,056         11         26      3,464      8,559     41,742    103,142     45,643     112,783
2........................................          0          0          0          0        433      1,070     21,062     52,044     21,495      53,114
3........................................          0          0          0          0          0          0     20,936     51,733     20,936      51,733
4........................................          0          0          0          1          0          0      3,233      7,989      3,234       7,990
5 A-B....................................        150        370          0          0        263        650      1,310      3,238      1,723       4,258
6 A-B....................................          0          0        199        491          0          0      7,829     19,345      8,028      19,836
                                          ------------
    Species Total........................        577      1,426        210        518      4,160     10,279     96,113    237,491    101,059     249,714
------------------------------------------
                                                                  Slender Orcutt Grass
--------------------------------------------------------------------------------------------------------------------------------------------------------
1 A-I....................................     18,527     45,780         37         92          0          0      4,702     11,618     23,266      57,490
2 A-C....................................         33         81          0          0         53        130      5,014     12,390      5,100      12,601
3........................................      6,226     15,384        437      1,080      6,320     15,617      7,463     18,441     20,446      50,522
4........................................          0          0          0          1      7,096     17,534      4,577     11,310     11,674      28,845
5 A-B....................................          0          0          5         13         78        192      1,613      3,986      1,696       4,191
6........................................          0          0          0          0          0          0      8,853     21,875      8,853      21,875
                                          ------------
    Species Total........................     24,786     61,245        480      1,186     13,547     33,473     32,222     79,620     71,035     175,524
------------------------------------------
                                                                      Solano Grass
--------------------------------------------------------------------------------------------------------------------------------------------------------
1........................................        130        321          0          0          0          0         62        153        192         474
2........................................         94        233        257        636      1,137      2,809      5,665     13,997      7,153      17,675
                                          ------------
    Species Total........................        224        554        257        636      1,137      2,809      5,727     14,150      7,345      18,149
------------------------------------------
                                                                 Succulent Owl's Clover
--------------------------------------------------------------------------------------------------------------------------------------------------------
1........................................          0          0          0          0          0          0      1,051      2,598      1,051       2,598
2........................................          0          0          0          0          0          0     14,131     34,917     14,131      34,917
3 A-B....................................        427      1,056         11         26      4,566     11,283     58,348    144,177     63,353     156,542
4........................................          5         13         56        139          0          0     33,009     81,565     33,071      81,717
5........................................          0          0          0          1          0          0     11,888     29,374     11,888      29,375
6 A-B....................................        150        371        174        429        259        639      1,141      2,819      1,723       4,258
                                          ------------
    Species Total........................        583      1,440        241        595      4,825     11,922    119,569    295,450    125,217     309,407
--------------------------------------------------------------------------------------------------------------------------------------------------------

Species Specific Criteria

    After developing the general criteria described previously, we 
conducted a species by species review based on the specific habitat 
requirements, primary constituent elements, and individual threats to 
each species addressed in this proposed rule. The specific unit 
description for each species is described below.

Conservancy Fairy Shrimp Criteria

    In proposing critical habitat units for Conservancy fairy shrimp, 
we evaluated the life history and current distribution of the species 
described in the background section of this rule, the primary 
constituent elements described in the primary constituent element 
section of this rule, and the threats to the species described above, 
in addition to those described below. This information allowed us to 
determine which areas are likely to contribute to the conservation of 
Conservancy fairy shrimp and to delineate units so that threats to 
these species might be minimized.
    Conservancy fairy shrimp are known only from eight disjunct areas: 
the Vina Plains area and vicinity in southern Tehama and northern Butte 
County; Jepson Prairie and Suisun Slough in southern Solano County; 
Sacramento National Wildlife Refuge in Glenn and Colusa counties; near 
Caswell Memorial State Park in Stanislaus County; near Haystack 
Mountain in Merced County; at the San Luis National Wildlife Refuge 
Complex in western Merced County, and at the Mutau Flat area in the Los 
Padres National Forest area of northern Ventura County.
    Conservancy fairy shrimp continues to be threatened by all of the 
factors which lead to the original listing of this species, primarily 
habitat loss through agricultural conversion and

[[Page 59914]]

urbanization. Helm (1998) found that most Conservancy fairy shrimp 
occurrences were on Anita, Pescadero or Peters Clay soils. These 
fertile, basin rim soils were among the first areas converted to 
agriculture in the 19th century, suggesting that a disproportionate 
amount of Conservancy fairy shrimp habitat may have been lost early in 
California's history (Helm 1998).
    In addition to direct habitat loss, almost one third of the known 
occurrences of Conservancy fairy shrimp are threatened by alterations 
of hydrology, including the construction of drainage channels, diking, 
and inappropriate water diversion within managed wetland areas in 
Merced and Solano counties (CNDDB 2002). Other threats include possible 
introduction of predators (e.g., bullfrogs, crayfish, fish) either 
directly or through alteration of drainage patterns (CNDDB 2002). Off-
road vehicles also represent a threat to the continued survival of 
Conservancy fairy shrimp populations (Hathaway et al. 1996). In some 
cases, special management actions may be necessary to prevent these 
threats from extirpating occurrences of Conservancy fairy shrimp.

Conservancy Fairy Shrimp Review

    We conducted a regional review across the range of Conservancy 
fairy shrimp to evaluate and select areas that are essential to the 
conservation of the species and that may require special management 
actions. Important factors we considered were the known presence of the 
species and the presence of the primary constituent elements essential 
to the conservation of the species. A specific description of each area 
is outlined below.

Unit 1, Vina Plains Unit, Butte and Tehema Counties (20,546 ha (50,769 
ac))

    This unit is proposed as critical habitat for Conservancy fairy 
shrimp because it contains occurrences of the species (CNDDB 2002) 
within vernal pools found on Anita clay and Tuscan loam soils (EPA 
1994, Holland 1998, Tehama County 1999, USDA 2001). These soils support 
pool types that remain inundated for sufficient periods of time to 
allow Conservancy fairy shrimp to hatch, mature, and reproduce, but do 
not contain water during the summer preventing the invasion of predator 
species such as bullfrogs and fish. This unit represents the northern 
extent of Conservancy fairy shrimp range.
    Conservancy fairy shrimp in this area occupy vernal pools that are 
classified as Northern Hardpan by Sawyer and Keeler-Wolf (1995) and 
occur on the Tuscan, Red Bluff, and Riverbank geologic formations. 
Within this unit vernal pools occur in complexes with a range of pool 
sizes, from over several acres to less than a tenth of an acre, in 
areas of hummocky ground on old terraces above recent river flood 
plains below the foothills (Alexander and Schlising 1997, Keeler-Wolf 
et al. 1998). The boundaries of this unit were delineated to include 
the interconnected pools, swales, and interconnected uplands mapped by 
Holland (1998) that contribute to the filling and drying of the vernal 
pools where Conservancy fairy shrimp occur, and maintain suitable 
periods of pool inundation, water quality, and soil moisture for 
Conservancy fairy shrimp hatching, growth and reproduction, and 
dispersal, but not necessarily every year.
    This unit includes relatively undisturbed, hydrologically intact 
vernal pool habitats, that will likely continue to support natural 
vernal pool ecosystem processes and maintain suitable habitat 
conditions for Conservancy fairy shrimp. This area also provides 
seasonal habitat for waterfowl and other migratory bird species which 
aid in the dispersal of Conservancy fairy shrimp among vernal pools 
within the unit, and between other habitats across the species range.
    The majority of the lands included within this unit are privately 
owned. This unit contains TNC's Vina Plains preserve as well as other 
TNC lands 2,264 ha (5,660 ac) and conservation easements 4,348 ha 
(10,870 ac). The NRCS also holds WRP conservation easements or 
agreements on 57 ha (142 ac). The preserve contains over 300 species of 
plants, and diverse communities of aquatic invertebrates. Since the 
1960's, the Vina Plains area has been the focus of a number of research 
projects, including long-term adaptive management and monitoring 
efforts evaluating of the effects of grazing and fire on vernal pool 
plants, animals, and ecosystems (Griggs 2000). Much of the basic life 
history information known about vernal pool crustaceans was collected 
at Vina Plains (e.g. Lanway 1974, Ahl 1991, Syrdahl 1993, Gallagher 
1996). The results of this research have provided crucial information 
to guide management and monitoring of vernal pool ecosystems and to 
identify factors which influence population dynamics of a number of 
endangered species, including Conservancy fairy shrimp. The Vina Plains 
is open to the public and provides excellent outreach and educational 
opportunities. In addition to TNC, the importance of vernal pool 
habitats in this area has been recognized by the CDFG, the Service, the 
EPA, the CNPS, the NRCS's WRP, and by researchers at the CSU at Chico, 
who have all supported research and conservation efforts for 
Conservancy fairy shrimp and other vernal pool species within this 
unit. Urban development north of Chico and the conversion of grazed 
lands to more intensive agricultural uses threaten vernal pool habitat 
within this unit.
    The Vina Plains Unit extends from south of Deer Creek to north of 
Rock Creek and the Chico Airport near the City of Chico. State Highway 
99 bisects this unit. The western boundary generally parallels the 
Southern Pacific Railway line. The eastern boundary of this unit 
extends to the boundary of the East Red Bluff watershed. This unit 
overlaps Unit 7 for vernal pool fairy shrimp and Unit 3 for vernal pool 
tadpole shrimp and contains part of Unit 1 for hairy Orcutt grass, Unit 
2 for Greene's tuctoria, Unit 1 for Hoover's spurge, and Unit 4 for 
slender Orcutt grass. Additional sensitive species occurring in this 
unit include California linderiella and Bogg's Lake hedge-hyssop.

Unit 2, Colusa Unit, Sacramento Valley, Glenn and Colusa Counties 
(5,718 ha (14,129 ac))

    This unit is proposed as critical habitat for Conservancy fairy 
shrimp because it contains occurrences of the species within large, 
alkaline vernal pools formed on the Modesto geologic formation on 
Willows and Riz soils that provide the primary constituent elements 
essential to the conservation of the Conservancy fairy shrimp (Holland 
1998, Silveira 2000, CNDDB 2002). Conservancy fairy shrimp in this area 
occupy pools that are often large, shallow and alkaline. They may 
display white salt deposits following pool drying. These pool types 
remain inundated for sufficient periods of time to allow Conservancy 
fairy shrimp to hatch, mature, and reproduce, but do not contain water 
during the summer, preventing the invasion of predator species such as 
bullfrogs and fish. This area is important to maintain the diversity of 
habitats in which Conservancy fairy shrimp occur.
    This unit is primarily located on the Sacramento National Wildlife 
Refuge (5,126 ha (12,816 ac)). Any additional lands within this unit 
are privately owned. The refuge supports over 355 native plant taxa, 
including a number of rare alkaline species (Oswald and Silveira 1995). 
Vernal pool habitats on the refuge are specifically managed for

[[Page 59915]]

the conservation of listed species, and to promote habitat for 
migratory birds and waterfowl. As a result this unit also provides 
essential habitat for avian species that aid in the dispersal of 
Conservancy fairy shrimp and other vernal pool crustacean cysts. The 
Sacramento National Wildlife Refuge contains the only remnants of the 
widespread Colusa Plains vegetation that once covered the entire Colusa 
Basin (Silveira 2000). Vernal pool habitats within the area have become 
greatly fragmented and isolated from other habitats in the region.
    The boundaries of this unit were delineated to include the 
interconnected pools, swales, and interconnected uplands mapped by 
Holland (1998) that contribute to the filling and drying of the vernal 
pools where Conservancy fairy shrimp occur, and maintain suitable 
periods of pool inundation, water quality, and soil moisture for 
Conservancy fairy shrimp hatching, growth and reproduction, and 
dispersal, but not necessarily every year.
    This unit occupies vernal pool habitat east of Interstate 5 to the 
Colusa Trough from Riz Road on the north and Delevan Road on the south. 
This unit coincides with vernal pool fairy shrimp Unit 10, vernal pool 
tadpole shrimp Unit 5, Unit 3 for hairy Orcutt grass, and Unit 3 for 
Hoover's spurge. Other rare vernal pool species found in this unit 
include pappose spikeweed, Fremont's goldfields, alkali goldfields, 
Scribe's popcorn flower, Hoover's downingia, folded downingia, 
Heckard's peppergrass, heartscale, brittlescale, San Joaquin 
spearscale, Ferris' milk-vetch, spike-primrose, sessile mousetail, and 
the federally listed as endangered palmate-bracted bird's beak.

Unit 3, Jepson Prairie Unit, Solano County (9,927 ha (24,529 ac))

    This unit is proposed as critical habitat for Conservancy fairy 
shrimp because it includes numerous occurrences of the species within 
one of the most pristine, intact vernal pool ecosystems remaining in 
California (Holland 1998, Solano County 1999, Solano County Farmland 
and Open Space 2001, CNDDB 2002). The unit boundary was drawn to 
include the vernal pools where Conservancy fairy shrimp occur, 
including the 32 ha (80 ac) Olcott Lake and other large playa pools 
associated with Solano Loam and Pescadero soil series. Conservancy 
fairy shrimp in this unit occupy vernal pool complexes extending from 
Jepson Prairie west towards the City of Fairfield. Within these 
complexes larger pools often occur with smaller pools and hogwallow 
depressions. Together the pools, swales, and associated uplands 
maintain the necessary timing and frequency of inundation for 
Conservancy fairy shrimp hatching, growth, and reproduction, but are 
dry during the summer. The relatively undisturbed, hydrologically 
intact condition of the Jepson Prairie increases the likelihood that it 
will continue to support natural vernal pool ecosystem processes and 
maintain suitable habitat conditions for Conservancy fairy shrimp. This 
unit also provides habitat for avian species that aid in the dispersal 
of Conservancy fairy shrimp and other vernal pool crustacean cysts.
    In addition to Conservancy fairy shrimp, the greater Jepson Prairie 
grassland area supports a diverse community of native plants and 
animals, including the only known occurrence of Delta green ground 
beetle, and occurrences of Solano grass, Colusa grass, California tiger 
salamander, vernal pool tadpole shrimp, vernal pool fairy shrimp, 
alkali milk-vetch, Bogg's Lake hedge-hyssop, legenere, California 
linderiella, and midvalley fairy shrimp. The southwestern portion of 
this unit contains vernal pool habitats near the Potrero Hills south of 
Travis Air Force Base. These vernal pool habitats occur in close 
proximity to tidal marshes and contain habitat for Contra Costa 
goldfields.
    This unit includes the Jepson Prairie Preserve, jointly managed by 
the Solano County Farmlands and Open Space Foundation and the UC 
Reserve System. Jepson Prairie has long been recognized as an 
outstanding example of vernal pool ecosystems. In 1987 NPS named Jepson 
Prairie a National Natural Landmark, a designation given to sites that 
provide high quality habitat for threatened or endangered species. 
Jepson Prairie is the target of ongoing conservation planning efforts 
and active management. As part of the UC Reserve System, this area 
provides critical research opportunities for scientists to study 
Conservancy fairy shrimp, and to determine their response to different 
management regimes. Conducting this research is essential to ensure the 
conservation of Conservancy fairy shrimp and other vernal pool species. 
This unit also contains land owned by the CDFG (319 ha (797 ac)), and 
State Land Commission (7 ha (17 ac)), as well as conservation easements 
held by TNC (623 ha (1,090)) and by NRCS under the WRP program (436 ha 
(1,090 ac). The unit also includes portions of Travis Air Force Base 
(DOD lands totaling 238 ha (596 ac)). Within the greater Jepson Prairie 
grassland area, existing vernal pools are threatened by agricultural 
conversion, landfill expansion, power plant construction, and utility 
maintenance. Urbanization in the vicinity of Fairfield and Suisun, and 
landfill expansion projects in the vicinity of the Protero Hills, 
threaten vernal pool habitats in the area.
    This unit occurs in the southern portion of Solano County, east and 
south of the City of Fairfield, south and southwest of the City of 
Dixon, and north of Nurse Slough and the confluence of the Sacramento 
and San Joaquin rivers. This unit contains Unit 3 for Colusa grass, 
Unit 2 for Solano grass, and overlaps with Unit 4 for Contra Costa 
goldfields. This unit is encompassed by Unit 11 for vernal pool tadpole 
shrimp and Unit 16 for vernal pool fairy shrimp.

Unit 4, Montezuma Unit, Solano County (603 ha (1,490 ac))

    This unit is proposed as critical habitat for Conservancy fairy 
shrimp because it contains vernal pools that support the necessary 
timing, frequency, and duration of inundation essential for Conservancy 
fairy shrimp feeding, sheltering, reproducing, and dispersing (Lipton 
in litt. 2002, Levine Fricke Restoration Corp 2000). This is the most 
recently discovered occurrence of Conservancy fairy shrimp, and one of 
the only areas where this species occurs in the saline-alkaline 
transition zone between vernal pools and tidal marshes.
    Most of the habitats within this unit are on private land, although 
portions of the Hill Slough Wildlife Area managed by the CDFG are also 
included within this unit. The primary threats to vernal pool habitats 
within this unit are alterations to hydrology from filling, diking, and 
dredging activities which may occur in the tidal marsh. This unit is 
also proposed so that special management actions may be taken to 
prevent the degradation of Conservancy fairy shrimp occurrences through 
alteration of the hydrology of their vernal pool habitats.
    This unit is located near the Suisun Marsh in southern Solano 
County, east of Montezuma Slough and west of Collinsville Road; the 
northernmost portion of this unit is bisected by Birds Landings Road. 
Portions of this unit coincide with Unit 12 for vernal pool tadpole 
shrimp. In addition to Conservancy fairy shrimp, this unit contains 
occurrences of other rare vernal pool species including vernal pool 
fairy shrimp, alkali milk-vetch and dwarf downingia.

[[Page 59916]]

Unit 5, Northern San Joaquin Valley Unit, Stanislaus County (302 ha 
(746 ac))

    This unit is proposed as critical habitat for Conservancy fairy 
shrimp because it contains the species within alkali sink vernal pools 
formed on Fresno series soils (CNDDB 2002). The unit boundary was 
designated to include the vernal pool complex mapped by Holland (1998) 
that maintains the necessary timing and frequency of inundation for 
Conservancy fairy shrimp hatching, growth, and reproduction, but is dry 
in the summer. The minimum mapping unit of Holland (1998) of 16 ha (40 
ac) did not allow us to exclude all non-vernal pool areas from within 
the unit boundary. However, the entire unit is located within the San 
Joaquin River National Wildlife Refuge and restoration is currently the 
focus of conservation planning efforts by the Service. Additional 
restoration designed to enhance habitat for riparian species, as well 
as migratory birds and waterfowl, is also currently underway. This unit 
is proposed so that special management actions, including appropriate 
wetland management, can be taken to maintain the natural hydrology of 
the vernal pools where Conservancy fairy shrimp are known to occur. 
This unit is over 70 km (43 mi) from the nearest unit to the south and 
over 40 km (25 mi) from the nearest unit to the north. Such isolated 
populations may have genetic characteristics essential to overall long-
term conservation of the species (i.e. they may be genetically 
different than more central populations) (Lesica and Allendorf 1995, 
Fugate 1998).
    Lands within this unit form a mosaic of riparian habitat, wetlands, 
and grasslands. The San Joaquin River National Wildlife Refuge is the 
primary wintering site of 98 percent of the Aleutian Canada geese that 
winter in the Valley (October--April), and it is a major wintering and 
migration area for lesser and greater sandhill cranes, cackling Canada 
geese, and white-fronted geese. These migratory birds act as dispersal 
agents for Conservancy fairy shrimp and other vernal pool crustacean 
species.
    This unit is situated west of the City of Modesto and east of the 
confluence of the San Joaquin and Stanislaus rivers. Caswell Memorial 
State Park lies just north of this unit. This unit is bisected by the 
Hetch Hetchy Aqueduct and State Highway 132. This unit overlaps vernal 
pool fairy shrimp Unit 20. It is also contains California linderiella 
and California tiger salamander occurrences, in addition to a number of 
rare non-vernal pool species including the federally listed endangered 
riparian wood rat and riparian brush rabbit.

Unit 6, Merced Unit, Merced and Mariposa Counties (63,750 ha (157,525 
ac)

    This unit is proposed as critical habitat for Conservancy fairy 
shrimp because it contains occurrences of the species within large, 
playa vernal pools found on Raynor Cobbly clay soils on the Mehrten 
Formation (CNDDB 2001, EIP Associates 1999). These pool types provide 
the necessary length and timing of inundation essential for the 
conservation of Conservancy fairy shrimp. The Merced Unit encompasses 
the largest block of pristine, high density vernal pool grasslands 
remaining in California (Vollmar 1999). The relatively undisturbed, 
hydrologically intact condition of the unit increases the likelihood 
that it will continue to support natural vernal pool ecosystem 
processes and maintain suitable habitat conditions for Conservancy 
fairy shrimp. Genetic analyses of vernal pool tadpole shrimp revealed 
that occurrences in this unit were genetically different from other 
occurrences in California, and that this area was isolated from other 
vernal pool habitats (King 1996). Given that Conservation fairy shrimp 
and vernal pool tadpole shrimp are dispersed in similar ways, it is 
reasonable to assume that Conservancy fairy shrimp occurrences in this 
areas are also isolated from other occurrences throughout its range, 
and may also have unique genetic characteristics.
    Vernal pool habitats in eastern Merced County are seriously 
threatened by irrigated agriculture, upland housing development, and 
the proposed UC Merced campus and associated development. Effects 
associated with the UC campus and associated community could result in 
loss and degradation of vernal pool habitats within this unit. However, 
the recent draft biological opinion for the UC Merced campus and 
community developed environmental parameters which should reduce 
impacts to vernal pool habitats. Merced County and the CDFG are 
currently gathering data on presence, distribution, and microhabitat 
preferences of vernal pool crustaceans to aid in developing long-term 
conservation planning strategies for eastern Merced County. There is 
interest among ranch owners to establish conservation easements that 
will support rangeland and vernal pool conservation. The Conservancy 
fairy shrimp occurrence at the Flying M Ranch is already being managed 
through a conservation easement with TNC that conserves over 2,023 ha 
(5,000 ac) of vernal pool and upland habitat. Land ownership within the 
unit includes approximately 419 ha (1,048 ac) of DOD, (3 ha (8 ac) of 
BLM, and 10 ha (26 ac) of California State Parks. TNC has a total of 
4,513 ha (11,283 ac) of conservation easements within this unit.
    A majority of the vernal pool habitat in the Merced Unit is in 
eastern Merced County. The eastern edge of the unit overlaps into 
western Mariposa County and in the south it extends to Deadman Creek. 
The northern boundary parallels the Merced River. The unit is located 
east of Highway 99 and the City of Merced, Planada, and Le Grand. The 
eastern boundary extends into the low elevation foothills of the Sierra 
Nevada. The boundaries of this unit overlap with San Joaquin Valley 
Orcutt grass Units 2 and 3, Colusa grass Units 7, Greene's tuctoria 
Unit 6, succulent owl's-clover Units 3B, vernal pool fairy shrimp Unit 
22, and vernal pool tadpole shrimp Unit 15. Other sensitive vernal pool 
species found within this unit include California tiger salamander, 
shining navarretia, dwarf downingia, Bogg's Lake hedge-hyssop, western 
spadefoot toad, and California linderiella.

Unit 7, Grassland Ecological Unit, Madera, Merced and Stanislaus 
Counties (46,142 ha (114,016 ac))

    We propose this area as critical habitat for Conservancy fairy 
shrimp because it supports multiple occurrences of the species within 
large, playa vernal pools of the Edminstor and Kesterson soil series 
(Holland 1998, USDA 2001, CNDDB 2002). The unit boundary was drawn to 
include Conservancy fairy shrimp and the vernal pool complexes mapped 
by Holland (1998) where the species is known to occur. These features 
maintain the necessary length and timing of inundation for Conservancy 
fairy shrimp hatching, maturation, and reproduction, but are dry in the 
summer and do not support aquatic species such as fish or bullfrogs. 
Conservancy fairy shrimp are found in large numbers throughout this 
unit, making this area a potential source for propagules dispersing to 
Conservancy fairy shrimp habitats to the south in Ventura County, to 
the east in eastern Merced County, and to the north in Stanislaus 
County. This unit is also proposed as critical to ensure that special 
management actions are taken to prevent or reverse changes in 
hydrology, contamination from adjacent land use, and invasion by 
aquatic species that threaten Conservancy fairy shrimp occurrences 
within this unit.

[[Page 59917]]

    This area contains the largest intact vernal pool habitat for 
Conservancy fairy shrimp in the San Joaquin Valley (Holland 1998). This 
unit also provides essential habitat for migratory waterfowl that aid 
in the dispersal of Conservancy fairy shrimp and other vernal pool 
crustacean cysts. The Grassland Ecological Unit includes Kesterson, San 
Luis, and Merced National Wildlife Refuges (12,765 ha (31, 542 ac)), 
CDFG lands (1,703 ha (4,257 ac)), CDFG administration lands (1,052 ha 
(2,631 ac)), California State Parks (1,358 ha (3,394 ac)), and private 
lands protected by WRP easements or agreements (54 ha (134 ac)). 
Combined, these lands are known as the Grasslands Ecological Area, a 
66,773 ha (160,000 ac) area which supports the largest remaining areas 
of several rare valley floor habitats within the San Joaquin valley, 
including examples of alkali grasslands, alkali scrublands, wild rye 
grasslands, cotton wood riparian forests, vernal marshes, relict dune 
lands, and high quality vernal pool habitats.
    The unit lies north of the City of Los Banos, southwest of the City 
of Merced, and is bisected by the San Joaquin River. This unit 
represents Unit 23 for vernal pool fairy shrimp and Unit 16 for vernal 
pool tadpole shrimp. The western half of this unit represents Unit 2 
for longhorn fairy shrimp and the eastern half represents Unit 8 for 
Colusa grass, and Unit 6 for Hoover's spurge. In addition to the 
species mentioned above, vernal pool smallscale, alkali milk-vetch, 
western spadefoot toad, and California linderiella are present within 
this unit as well.

Unit 8, Ventura County Unit, Ventura, Santa Barbara, and Los Angeles 
Counties (18,831 ha (46,531 ac))

    The Ventura County unit consists of one area in the north-central 
portion of Ventura County. Vernal pool fairy shrimp and Conservancy 
fairy shrimp are known to co-occur at relatively high elevation 
([sim]1,700 m (5,500 ft)) forested sites within the Los Padres National 
Forest. All of this unit is owned by the USFS. Almost all of the known 
localities that possess these two species within the state of 
California exist at much lower elevations in grassland habitats. The 
map polygon perimeter consists of an area that is known to contain 
vernal pool and Conservancy fairy shrimp occurrences and isolated pools 
that provide habitat for the two species. The Ventura County unit is 
essential for the conservation of Conservancy fairy shrimp because it 
contains high elevation ([sim] 1,700 m (5,500 ft)) ephemeral aquatic 
environments that are rarely associated with fairy shrimp. The Ventura 
County sites that are occupied by Conservancy fairy shrimp are 124 km 
(200 m) from other species occurrences in the Great Central Valley, 
thereby suggesting that the Ventura County population(s) is 
geographically isolated from the population(s) that occur farther east 
and north. Such isolated and peripheral populations may have genetic 
characteristics that are different than more central populations, and 
may be important for conservation (Lesica and Allendorf 1995, Fugate 
1998).

Longhorn Fairy Shrimp Criteria

    In proposing critical habitat units for longhorn fairy shrimp we 
evaluated the life history and current distribution of the species 
described in the background section of this rule, the primary 
constituent elements described in the primary constituent element 
section of this rule, and the threats to the species described under 
vernal pool crustaceans above and additional threats described below. 
This information allowed us to determine which areas are likely to be 
essential to the conservation of these species.
    Longhorn fairy shrimp are currently known from three locations, 
Altamont Pass area at the Contra Costa and Alameda county line, San 
Luis National Wildlife Refuge Complex in western Merced County, and the 
Soda Lake area in San Luis Obispo County. Longhorn fairy shrimp near 
Soda Lake occur both on protected land within the Carrizo National 
Monument, and on private land. The occurrences on private land are 
threatened by proposed development of ranchettes, production of animals 
used in biotechnology industries, and road construction. Longhorn fairy 
shrimp occurrences in the Altamont Pass area in Contra Costa and 
Alameda counties have been heavily impacted by wind energy development, 
although some of these occurrences are currently protected from 
development on land owned by the East Bay Regional Parks District 
(EBRPD) (Eng et al. 1990, EBRPD 2001). Longhorn fairy shrimp are 
protected from development on the Kesterson National Wildlife Refuge in 
Merced County, however, these occurrences are threatened by wetland 
management practices that have led to prolonged inundation of longhorn 
fairy shrimp habitats and inadvertent introduction of fish and 
bullfrogs (CNDDB 2001).
    In areas where longhorn fairy shrimp habitats have been protected, 
the species may be still be threatened if adequate monitoring and 
management is not conducted. Management and monitoring are necessary to 
recognize and protect populations from indirect effects, such as 
changes in hydrology, contamination, siltation, erosion, competition 
with non-native species, and human-related disturbance, such as off 
road vehicle use.

Longhorn Fairy Shrimp Unit Review

    We conducted a review of the currently known range of longhorn 
fairy shrimp to evaluate and select areas that are essential to the 
conservation of the species and that may require special management. 
Important factors we considered were the presence of the species and 
the primary constituent elements essential to the conservation of the 
species. A specific description of each area is outlined below.

Unit 1, Altamont Hills Unit A and B, Contra Costa and Alameda Counties 
(322 ha (795 ac))

    This unit is proposed as critical habitat for longhorn fairy shrimp 
because it supports occurrences of the species within clear depression 
pools in sandstone outcrops (Eriksen and Belk 1999, EBRPD 2001, CNDDB 
2002). These pool types become inundated during winter rains and hold 
water for sufficient lengths of time necessary for longhorn fairy 
shrimp incubation, reproduction, dispersal, feeding, and sheltering, 
but are dry during the summer and do not necessarily fill with water 
every year; This is an unique habitat for longhorn fairy shrimp, and 
helps to maintain a diversity of habitats for the species. The Altamont 
Hills Unit is an important area for longhorn fairy shrimp because it 
represents the northern limit of the species range, and is one of only 
3 locations where the species is known to occur throughout their entire 
range. Longhorn fairy shrimp in the Altamont Hills Unit are located 
about 100 km (60 mi) northwest of the next known occurrence at 
Kesterson National Wildlife Refuge in Merced County (Eriksen and Belk 
1999). It is likely these occurrences have genetic characteristics that 
differ from other occurrences in other portions of the species range, 
and these characteristics may be important for the conservation of 
longhorn fairy shrimp (Fugate 1992, 1998). Each of these locations 
reduces the probability that a chance event would result in the 
extinction of the species.
    This unit is located primarily on EBRPD and Contra Costa Water 
District land. This unit is located in Altamont Hills north and 
northeast of the City of Livermore, and consists of two subunits, both 
near the Contra Costa and Alameda county line. Subunit A is located in 
Contra Costa County directly north of

[[Page 59918]]

the Alameda County line near the Vasco Caves. Subunit B is located 
directly in Alameda County just south of the Contra Costa County line 
in the vicinity of Brushy Peak. A large number of federally listed and 
sensitive species are found within this area, including the California 
red legged frog, San Joaquin kit fox, California tiger salamander and 
California linderiella.

Unit 2, Grassland Ecological Unit, Madera, Merced and Stanislaus 
Counties (29,817 ha (73,677 ac))

    This unit is proposed as critical habitat for longhorn fairy shrimp 
because it contains turbid alkaline vernal pools on Edminster loam and 
Turlock sandy loam that support occurrences of the species (USDA 2001, 
Holland 1998, CNDDB 2002). This is the only location where longhorn 
fairy shrimp occur in the Central Valley of California. Longhorn fairy 
shrimp within this unit are threatened by altered hydrology and 
invasion of aquatic predators. This unit is also designated so that 
special management actions can be taken to maintain the appropriate 
timing, frequency, and duration of inundation of longhorn fairy shrimp 
habitat essential to the conservation of longhorn fairy shrimp within 
managed wetland areas.
    This unit is over 209 km (130 mi) from the longhorn fairy shrimp 
occurrence to the south, and over 80 km (50 mi) from longhorn fairy 
shrimp occurrences to the north. This occurrence is likely genetically 
different from the two other occurrences (Fugate 1992, 1998). Longhorn 
fairy shrimp are known from only 3 locations, and each of these 
locations is important to the conservation of this species by providing 
a buffer against catastrophic or stochastic events which could 
extirpate any one occurrence and seriously reduce the likelihood of 
survival and recovery of the species as a whole.
    This unit includes natural habitats within the San Joaquin River 
watershed. The Grassland Ecological Unit includes Kesterson, San Luis, 
and Merced National Wildlife Refuges (9,303 ha (23, 258 ac)), CDFG 
lands (1,703 ha (4,257 ac)), CDFG administration lands (1,052 ha (2,631 
ac)), California State Parks (1,358 ha (3,394 ac)), private lands 
protected by WRP easements or agreements (54 ha (134 ac)), and numerous 
other Federal and private conservation easements. Combined, these lands 
are known as the Grasslands Ecological Area, a 66,773 ha (160,000 ac) 
area which supports the largest remaining areas of several rare valley 
floor habitats within the San Joaquin valley, including examples of 
alkali grasslands, alkali scrub lands, wild rye grasslands, cotton wood 
riparian forests, vernal marshes, relict dune lands, and high quality 
vernal pool habitats. Threats to vernal pool habitats in this unit 
include agricultural conversion, changes in hydrology, contamination 
from adjacent land use, and invasion by aggressive plants.
    The unit lies north of the City of Los Banos, southwest of the City 
of Merced, and is bisected by the San Joaquin River. This unit overlaps 
Unit 23 for vernal pool fairy shrimp, Unit 16 for vernal pool tadpole 
shrimp, and Unit 7 for Conservancy fairy shrimp. In addition to the 
species mentioned above, vernal pool smallscale, Alkali milk-vetch, 
western spadefoot toad, and California linderiella are present within 
this unit as well.

Unit 3, Carrizo Plain Unit, San Luis Obispo, Kern, and Monterey 
Counties (10,466 ha (25,862 ac))

    This unit is proposed as critical habitat for longhorn fairy shrimp 
because it contains occurrences of the species living within Northern 
Claypan type vernal pools as described by Sawyer and Keeler-Wolf (1995) 
(CNDDB 2001). Longhorn fairy shrimp in the Carrizo Unit are found in 
shallow alkaline vernal pools within a Valley Saltbush Scrub matrix 
adjacent to the 1214 ha (3,000 ac) Soda Lake, the largest alkali 
wetland in central and southern California, which provides a winter 
haven for thousands of migratory birds.
    The Carrizo Plain Unit represents the southern extent of the range 
of longhorn fairy shrimp. Longhorn fairy shrimp in the Carrizo Plain 
Unit are located 235 km (146 mi) southeast of the closest known 
occurrences at Kesterson National Wildlife Refuge in Merced County 
(Eriksen and Belk 1999). Such isolated populations may have genetic 
characteristics essential to overall long-term conservation of the 
species (Fugate 1998). The Carrizo Plain contains examples of native 
bunch grass, needle grass, and blue grass grasslands, as well as 
populations of federally listed San Joaquin kit fox, blunt nosed 
leopard lizard, giant kangaroo rat, California jewel flower, Lost Hills 
salt brush, Kern mallow and San Joaquin wooly threads (The Nature 
Conservancy 2001). North of the Carrizo Plain, vernal pools that occur 
along the San Andreas fault are small sag pond types surrounded by 
annual grassland or Interior Coast Range Saltbush Scrub (Keeler-Wolf et 
al. 1998). The Carrizo Plain Unit contains portions of the Carrizo 
Plain National Monument administered by the BLM, TNC, and the CDFG. The 
BLM lands within the unit total approximately 6,220 ha (15,549 ac) and 
the CDFG lands total approximately 93 ha (233 ac). Other vernal pool 
habitats in the unit are located on private land.
    This unit is located in the vicinity of California Valley and Soda 
Lake. State Highway 58 is located north of the unit. Most of the 
habitat is east of Soda Lake Road, however, Soda Lake Road crosses 
through the western edge of the unit in several areas. To the east, the 
unit is bordered by the San Andreas Rift Zone. This unit coincides with 
vernal pool fairy shrimp Unit 25.

Vernal Pool Fairy Shrimp Criteria

    In proposing critical habitat units for vernal pool fairy shrimp we 
evaluated the life history and current distribution of the species, the 
primary constituent elements, and the current threats to the species. 
This information allowed us to determine which areas are likely to 
contribute to the conservation of vernal pool fairy shrimp and to 
delineate units so that threats to these species might be minimized.
    The historic range of vernal pool fairy shrimp extended throughout 
the low and mid-elevation regions of the Central Valley into southern 
and coastal California and southern Oregon Agate Desert. Vernal pool 
fairy shrimp have been extirpated from a number of their historic 
occurrences as a result of urban development and conversion to 
agriculture. Rapid urbanization in Placer, Sacramento, and Tehama 
counties, California, has accounted for the majority of recent vernal 
pool fairy shrimp extirpations, although conversion to agriculture in 
San Joaquin, Merced, and other counties also has contributed to the 
continued decline of this species.
    Remaining vernal pool fairy shrimp occurrences continue to be 
threatened by all of the factors that historically led to the decline 
of this species. CNDDB (2001) estimates that 34 percent of the 
remaining occurrences of this species are threatened by development and 
agricultural conversion. Another 15 percent are threatened by military 
activities (CNDDB 2001). An additional 15 percent are threatened by 
operations and maintenance activities within utility and transportation 
right-of-ways, including grading, discing, and trenching activities 
which destroy the topographical features necessary for vernal pool 
habitats to support occurrences of vernal pool fairy shrimp (CNDDB 
2001). Pesticide and herbicide use within utility easements also 
threaten many occurrences of vernal pool fairy shrimp (CNDDB 2001). 
Other vernal pool fairy shrimp occurrences are

[[Page 59919]]

threatened by off road vehicle use, logging, mining, vandalism, 
dumping, and expansion of landfills (CNDDB 2001).
    Numerous occurrences of vernal pool fairy shrimp are threatened by 
altered hydrology. In some cases vernal pools have been altered so that 
they contain water year round, allowing predators such as bullfrogs and 
fish to colonize vernal pool habitats (CNDDB 2001). In other cases 
artificial run off has resulted in the delivery of materials that 
destroy vernal pool water quality, including sediment from cement 
plants, pesticides from vineyards and other irrigated agricultural 
lands, pesticides from golf courses, and sediment from surrounding 
developments (CNDDB 2001).

Vernal Pool Fairy Shrimp Unit Review

    We conducted a regional review across the range of vernal pool 
fairy shrimp to evaluate and select vernal pool habitats that are 
essential to the conservation of the species and that require special 
management. Important factors we considered were the known presence of 
vernal pool fairy shrimp and the presence of vernal pools and vernal 
pool complexes supporting the hydrological characteristics necessary to 
provide the primary constituent elements essential to the conservation 
of the species.
    We identified areas that support high numbers of vernal pool fairy 
shrimp occurrences identified by CNDDB (2002) within vernal pool 
complexes containing the primary constituent elements for the species 
mapped by Holland (1998) and a number of other sources throughout the 
range of the species. We have identified areas necessary to conserve 
the species by maintaining a portion of the species current range and 
distribution and including some of the different kinds of habitats in 
which the species is known to occur. However, as is the case with all 
critical habitat designations, areas outside of this designation may 
still prove to be necessary to the recovery of this species. A 
description of each area is outlined below.

Oregon

    Vernal pool fairy shrimp are the only species addressed in this 
proposed rule that occur in Oregon. Four units in Oregon are proposed 
as essential to the conservation of vernal pool fairy shrimp. The 
Oregon units occur approximately 200 km (125 mi) north of the nearest 
unit proposed for this species in California.

Unit 1A, B, C ,D, E, F, and G, North Agate Desert Unit, Jackson County 
(862 ha (2,130 ac))

    This unit consists of seven subunits, all located to the north of 
Little Butte Creek. Three of the subunits are west of the Rogue River, 
and the remaining four are to the east. All but one of these subunits 
are located to the south of U.S. Route 234 (Sam's Valley Highway). The 
one remaining unit is located to the east of the Rogue River, about 2.4 
km (1.5 mi) north of the confluence with Reese Creek. This unit 
represents the northern limit of the species' distribution and 
therefore may contribute significantly to the species' genetic 
diversity (Lesica and Allendorf 1995). It is of sufficient size to 
sustain the natural ecosystem processes (e.g., fires) that have 
historically influenced vernal pool habitat and is disjunct from the 
nearest other unit proposed for Oregon, Unit 4, by over 3.2 km (2 mi).

Unit 2A, B, C, D, and E, White City East Unit, Jackson County (911 ha 
(2,251 ac))

    This unit consists of five subunits, located east of U.S. Route 62 
(Crater Lake Highway) and south and southeast of Dutton Road. The 
largest and easternmost of the subunits occurs just to the east and 
north of Agate Lake. This unit provides the easternmost extent of the 
species' range in Oregon. It represents a significant component of the 
species' original range in the state and is of a sufficient size to 
sustain the natural ecosystem processes (e.g., fires) that have 
historically influenced vernal pool habitat. It is disjunct by more 
than 1.6 km (1 mi) from Unit 3, White City West, and by approximately 
5.6 km (3.5 mi) from the North Agate Desert Unit.

Unit 3A, B, and C, White City West Unit, Jackson County (931 ha (2,301 
ac))

    This unit consists of three subunits, located west of Agate Road, 
south of the Rogue River, and east of Bear Creek. This unit contains 
the best remaining examples of the original Agate Desert mounded 
prairie habitat. It is of sufficient size to sustain the natural 
ecosystem processes (e.g., fires) that have historically influenced 
vernal pool habitat; it is disjunct from the White City East Unit by 
more than 1.6 km (1 mi) and from the Table Rocks Unit by over 2.4 km 
(1.5 mi).
    We believe that, taken together, the proposed Agate Desert units 
(Units 1-3) comprise a functional vernal pool complex consisting of 
vernal pools, mounded prairie and associated uplands, where natural 
processes, including connectivity, function within or near the natural 
range of variability. Each of the three proposed Agate Desert units is 
essential to the conservation of vernal pool fairy shrimp populations 
in the Agate Desert.

Unit 4A and B, Table Rocks Unit, Jackson County (361 ha (892 ac))

    This unit consists of two subunits, located on two flat-topped 
mesas known as Upper and Lower Table Rocks, situated north and west of 
the Rogue River. These rimrock features are remnants of ancient lava 
flows that filled portions of the Rogue River nearly 10 million years 
ago (Bureau of Land Management (BLM) 1998). Subsequent erosion of 
softer geologic layers has left these harder, andesite (volcanic rock) 
formations rising some 245 m (800 ft) above the present Rogue Valley. 
Vernal pools on the Table Rocks differ from those of the Agate Desert, 
in that they are formed over an impervious layer of bedrock. This unit 
represents a unique habitat for vernal pool fairy shrimp in Oregon; 
Table Rocks fairy shrimp populations differ ecologically from fairy 
shrimp populations in the Agate Desert. The Table Rocks Unit is 
disjunct from the North Agate Desert Unit by over 3.2 km (2 mi), and 
from the White City West Unit by approximately 2.4 km (1.5 mi).

California

Unit 5, Redding Unit, Shasta County (1,849 ha (4,569 ac))

    This unit is proposed as critical habitat for vernal pool fairy 
shrimp because it contains the largest intact vernal pool habitat in 
the northern portion of vernal pool fairy shrimp's range in California. 
Occurrences of the species (CNDDB 2002) within vernal pools mapped by 
Holland (1998) are found on old alluvial terraces above the Sacramento 
River and often on Redding and Corning soil complexes (Shasta County 
2001). Generally these pools are small in size, although the Stillwater 
Plains area supports unique pools which are several acres in size. 
These vernal pools provide feeding and sheltering habitat for the 
species and remain inundated for sufficient lengths of time to allow 
vernal pool fairy shrimp to hatch, mature, and reproduce.
    The boundaries of the unit were delineated to include the 
interconnected pools, swales, and associated uplands mapped by Holland 
(1998) that contribute to the filling and drying of the vernal pools 
where vernal pool fairy shrimp occur, and which maintain suitable 
periods of pool inundation, water quality, and soil moisture for vernal 
pool fairy shrimp hatching, growth, reproduction, and dispersal.

[[Page 59920]]

    This unit supports systems of hydrologically interconnected pools 
and swales within a matrix of surrounding uplands that together form 
hydrologically and ecologically functional units called vernal pool 
complexes. These features contribute to the filling and drying of the 
vernal pool, and maintain suitable periods of pool inundation, water 
quality, and soil moisture for vernal pool crustaceans to complete 
their life-cycle.
    This unit represents contains all of the primary constituent 
elements for the species and comprises the northern extent of the 
species range in California. Because occurrences within this unit are 
at the limit of the species range in California they may have genetic 
characteristics essential to overall long-term conservation of the 
species (i.e., they may be genetically different than more central 
populations) (Fugate 1992, 1998, Lesica and Allendorf 1995).
    Most of the land included within this unit is privately owned. The 
BLM owns 17 ha (42 ac) within this unit and a further 52 ha (130 ac) is 
private land protected under conservation easement or agreement as part 
of the Wetlands Reserve Program (WRP). The Stillwater Plains 
Conservation Bank, specifically established to contribute to the 
recovery of vernal pool fairy shrimp, is located within this unit. The 
City of Redding and other local and state planning organizations are 
currently developing a HCP to provide for the conservation of vernal 
pool fairy shrimp. This unit would provide an area where conservation 
efforts for vernal pool fairy shrimp could take place.
    This unit is located in the area east of the Redding Municipal 
Airport between Airport Road to the west and Deschutes Road to the 
east. The unit extends to Dersch Road in the south and towards Lassen 
Park Highway in the north. This unit comprises a portion of the 
Stillwater Plains. This unit overlaps slender Orcutt grass Unit 2B and 
vernal pool tadpole shrimp Unit 1. Other sensitive species occurring 
within this unit include Red Bluff dwarf rush (Juncus leiospermus var. 
leiospermus), California linderiella (Linderiella occidentalis), 
Henderson's bent grass (Agrostis hendersonii), and four angled spike 
rush (Eleocharis quadrangulata).

Unit 6, Red Bluff Unit, Tehama County (18,562 ha (45,865 ac)

    This unit is proposed as critical habitat for vernal pool fairy 
shrimp because it contains the species (CNDDB 2002) within vernal pools 
mapped by Holland (1998) and the pools contain water for sufficient 
periods of time necessary for vernal pool fairy shrimp incubation, 
reproduction, dispersal, feeding, and sheltering. Vernal pool fairy 
shrimp within this unit occur within vernal pools formed on alluvial 
terraces west of the Sacramento River and associated with Newville/
Corning and Redding/Corning soil complexes (USDA 2001) exhibiting well 
developed mima mound topography. The vernal pools within this unit are 
generally small and may not be inundated long enough to support other 
longer-lived vernal pool species.
    The boundaries of the unit were delineated to include the 
interconnected pools, swales, and associated uplands mapped by Holland 
(1998) that contribute to the filling and drying of the vernal pools 
where vernal pool fairy shrimp occur, and which maintain suitable 
periods of pool inundation, water quality, and soil moisture for vernal 
pool fairy shrimp hatching, growth, reproduction, and dispersal. This 
unit contains several large (i.e., over (4,068 ha) 10,000 ac) vernal 
pool habitat complexes. These areas are relatively undisturbed, 
hydrologically intact vernal pool habitats that will likely continue to 
support natural vernal pool ecosystem processes and maintain suitable 
habitat conditions for vernal pool fairy shrimp. This unit also 
provides essential habitat for migratory waterfowl that aid in the 
dispersal of vernal fairy shrimp and other vernal pool crustacean 
cysts.
    The majority of the lands included within this unit are privately 
owned. The CDFG owns 175 ha (433 ac) within this unit. Urban expansion 
from the city of Red Bluff, and agricultural conversion in other 
portions of the unit, threaten existing vernal pool fairy shrimp 
habitats throughout this unit. However, this unit also contains large 
private conservation areas established specifically to contribute to 
the recovery of vernal pool fairy shrimp and compensate for the loss of 
vernal pool habitat, including the 2,023 ha (5,000 ac) Tehama Fiber 
Farm mitigation area. CDFG's Thomes Creek Ecological Reserve is also 
located within this unit.
    This unit extends from southwest of Red Bluff at Red Bank Creek 
south to Thomes Creek. The eastern boundary includes the vernal pool 
habitat from the Southern Pacific Railroad near Coyote Creek south 
paralleling Interstate 5 to Thomes Creek. Other vernal pool species 
occurring within this unit include Boggs Lake hedge-hyssop (Gratiola 
heterosepela), Baker's navarretia (Navarretia leucocephala ssp. 
bakeri), Red Bluff dwarf rush, Douglas' pogogyne (Pogogyne douglasii), 
western spadefoot toad (Scaphiopus hammondi), legenere (Legenere 
limosa), California linderiella, Ahart's paronychia (Pyronychia 
ahartii), Henderson's bent grass, and dwarf downingia (Downingia 
pusilla).

Unit 7, Vina Plains Unit, Tehama, and Butte Counties (23,883 ha (59,015 
ac))

    This unit is proposed as critical habitat because it contains 
vernal pool fairy shrimp (CNDDB 2001) living within large vernal pool 
grassland areas that support aggregations or systems of hydrologically 
interconnected pools, swales, and other ephemeral wetlands and 
depressions within a matrix of surrounding uplands that together form 
hydrologically and ecologically functional units (EPA 1994, Holland 
1998, Tehama County 1999). The boundaries of this unit were delineated 
to include the interconnected pools, swales, and uplands mapped by 
Holland (1998) that contribute to the filling and drying of the vernal 
pools where vernal pool fairy shrimp occur, and maintain suitable 
periods of pool inundation, water quality, and soil moisture for vernal 
pool fairy shrimp to complete their life-cycles.
    The vernal pools within this unit contain water during the winter, 
and provide the necessary length and timing of inundation, water 
quality, and freedom from predation that allow vernal pool fairy shrimp 
to hatch, feed, reproduce, and shelter. Vernal pool fairy shrimp in 
this unit occur within Northern Volcanic Mudflow vernal pools, these 
pools are generally small and tend to be inundated for relatively short 
periods of time. Vernal pool fairy shrimp are also found within larger 
vernal pools forming on hardpans within this unit. These pools tend to 
be larger and longer lasting than Northern Volcanic Mudflow pools, and 
may also support occurrences of other, longer lived species such as 
Conservancy fairy shrimp.
    The pool types within this unit maintain the diversity of habitats 
in which vernal pool fairy shrimp are known to occur and provide 
relatively undisturbed, hydrologically intact vernal pool habitats that 
will likely continue to support natural vernal pool ecosystem processes 
and maintain suitable habitat conditions for vernal pool fairy shrimp. 
This unit also provides habitat for migratory waterfowl that aid in the 
dispersal of vernal pool fairy shrimp and other vernal pool crustacean 
cysts.
    The majority of the lands included within this unit are privately 
owned. This unit contains The Nature Conservancy's (TNC) Vina Plains 
preserve as well as other TNC lands 2,264 ha (5,660 ac) and 
conservation

[[Page 59921]]

easements 4,348 ha (10,870 ac). Other ownership within this unit 
includes 57 ha (142 ac) of private land protected under conservation 
easement or agreement under the Natural Resource Conservation 
Services's (NRCS) Wetland Reserve Program (WRP). The Vina Plains area 
has been the focus of a number of research projects, including long-
term adaptive management and monitoring efforts evaluating the effects 
of grazing and fire on vernal pool plants, animals, and ecosystems 
(Griggs 2000). Much of the basic life history information known about 
vernal pool crustaceans was collected at Vina Plains (e.g., Lanway 
1974, Ahl 1991, Syrdahl 1993, Gallagher 1996). The importance of the 
Vina Plains area has been recognized by a number of state, local, and 
Federal agencies, and they have been the focus of several conservation 
planning efforts. TNC, CDFG, the Service, the EPA, the CNPS, the NRCS 
WRP, and researchers from California State University (CSU) at Chico 
have all supported research and conservation efforts for vernal pool 
species within this unit.
    This unit is located in the northeastern portion of the Sacramento 
Valley from Deer Creek in Tehama County to Chico in Butte County. The 
unit extends south and east of the Sacramento River paralleling the low 
elevation foothill region of the Sierra Nevada and represents the 
northeastern extent of vernal pool fairy shrimp's range in California. 
This unit coincides with Unit 3 for vernal pool tadpole shrimp, and 
incorporates Unit 1 for Conservancy fairy shrimp, Unit 4 for slender 
Orcutt grass, Unit 2 for Greene's tuctoria, Unit 1 for hairy Orcutt 
grass, Unit 1 for Hoover's spurge, and Units 1 and 2 for Butte County 
meadowfoam. Other vernal pool species occurring within this unit 
include Boggs Lake hedge-hyssop, Red Bluff dwarf rush, Douglas' 
pogogyne, western spadefoot toad, legenere, California linderiella, 
California tiger salamander (Ambystoma californiense), Ahart's 
paronychia, Henderson's bent grass, Sanford's arrowhead (Sagittaria 
sanfordii), and dwarf downingia.

Unit 8, Orland Unit, Tehama County (5,760 ha (14,233 ac)

    This unit is proposed as critical habitat for vernal pool fairy 
shrimp because it contains occurrences of the species and vernal pools, 
swales, and associated uplands that support vernal pool fairy shrimp 
(Holland 1998, Tehama County 2001, CNDDB 2002). Vernal pool fairy 
shrimp in this unit are found in vernal pools formed on alluvial 
terraces west of the Sacramento River and associated with Anita clay 
and Tuscan loam soils (USDA 1994). These vernal pools are generally 
small, and exhibit well developed mima mound topography. They contain 
water for sufficient periods of time necessary for vernal pool fairy 
shrimp incubation, reproduction, dispersal, feeding, and sheltering.
    The boundaries of this unit were delineated to include the 
interconnected pools, swales, and associated uplands mapped by Holland 
(1998) that contribute to the filling and drying of the vernal pools 
where vernal pool fairy shrimp occur, and maintain suitable periods of 
pool inundation, water quality, and soil moisture for vernal pool fairy 
shrimp hatching, growth and reproduction, and dispersal, but not 
necessarily every year. These features contribute to the filling and 
drying of the vernal pool, and maintain suitable periods of pool 
inundation, water quality, and soil moisture for vernal pool crustacean 
hatching, growth and reproduction, and dispersal.
    This unit contains large vernal pool habitat areas in the 
northwestern portion of the range of vernal pool fairy shrimp. These 
areas provide relatively undisturbed, hydrologically intact vernal pool 
habitats that will likely continue to support natural vernal pool 
ecosystem processes and maintain suitable habitat conditions for vernal 
pool fairy shrimp. These vernal pool habitats support systems of 
hydrologically interconnected pools and swales within a matrix of 
surrounding uplands that together form hydrologically and ecologically 
functional units called vernal pool complexes.
    This unit extends from the Tehama/Glenn county border in the south, 
west of Ingrahm Road and east of the Black Butte Reservoir, to the 
vicinity of Rice Creek in the north. This unit also contains a Pacific 
Gas and Electric (PG&E) pipeline mitigation area established 
specifically for the conservation of vernal pool fairy shrimp. Other 
vernal pool species occurring within this unit include Baker's 
navarretia, western spadefoot toad, Ahart's paronychia, and dwarf 
downingia. All the lands within this unit are privately owned.

Unit 9, Oroville Unit, Butte County (1,456 ha (3,598 ac))

    This unit is proposed as critical habitat for vernal pool fairy 
shrimp because it supports vernal pools, swales, and associated uplands 
mapped by Holland (1998) and by the EPA (1994) and contains vernal pool 
fairy shrimp (CNDDB 2001). Vernal pool fairy shrimp within this unit 
live within pools occurring primarily on the Tuscan geologic formation 
(Liss 2001, Keeler-Wolf et al. 1998), which are some of the few 
remaining examples of Northern Volcanic Mudflow vernal pools described 
by Sawyer and Keeler-Wolf (1995). Northern Volcanic Mudflow vernal 
pools are generally small and tend to be inundated for relatively short 
periods of time. These pool types are essential to maintain the 
diversity of habitats in which vernal pool fairy shrimp are known to 
occur. Vernal pool fairy shrimp are also found living in Northern 
Hardpan vernal pools within this unit. These pools tend to be larger 
and longer lasting than the Northern Volcanic Mudflow pools.
    The boundaries of the unit were delineated to include the 
interconnected pools, swales, and associated uplands mapped by Holland 
(1998) that contribute to the filling and drying of the vernal pools 
where vernal pool fairy shrimp occur, and which maintain suitable 
periods of pool inundation, water quality, and soil moisture for vernal 
pool fairy shrimp hatching, growth, reproduction, and dispersal. The 
majority of the lands included within this unit are privately owned. 
This unit contains Service lands (76 ha (187 ac)) and 7 ha (17 ac) of 
CDFG administered land. This unit contains a few areas that have been 
preserved within the City of Chico. However, the amount of vernal pool 
habitat currently protected within the unit is very small. Urban 
expansion, particularly in the vicinity of Chico, is the greatest 
threat to existing vernal pool habitats throughout this unit.
    This unit occupies an area from near Chico south to near the 
intersection of Highway 99 and State Route 149 in Butte County. The 
unit extends southeast of the Sacramento River paralleling the low 
elevation foothill region of the Sierra Nevada. This unit is part of 
Unit 4 for vernal pool tadpole shrimp, and incorporates Unit 3 for 
Greene's tuctoria, Unit 2 for hairy Orcutt grass, Unit 2 for Hoover's 
spurge, and Unit 3 for Butte County meadowfoam. Other vernal pool 
species occurring within this unit include Boggs Lake hedge-hyssop, Red 
Bluff dwarf rush, Douglas' pogogyne, western spadefoot toad, legenere, 
California linderiella, California tiger salamander, Ahart's 
paronychia, Henderson's bent grass, Sanford's arrowhead, and dwarf 
downingia.

[[Page 59922]]

Unit 10, Sacramento National Wildlife Refuge Unit, Glenn and Colusa 
Counties (5,718 ha (14,129 ac))

    This unit is proposed as critical habitat for vernal pool fairy 
shrimp because it contains occurrences of the species (CNDDB 2002) 
within the vernal pools and swales mapped by Holland (1998). Vernal 
pool fairy shrimp in this unit live within Northern Claypan vernal 
pools, as defined by Sawyer and Keeler-Wolf (1995). These vernal pools 
are associated with alkaline soils, such as Willows and Riz soils 
series, and typically form alkali playas which are larger and contain a 
more diverse species composition than the hardpan pools further south 
(Keeler-Wolf et al. 1998). These pools are inundated for a sufficient 
period of time to support all of the life history requirements of 
vernal pool fairy shrimp. Vernal pools on the Sacramento National 
Wildlife Refuge Complex , are often large, shallow and alkaline 
(Silveira 2000). Vernal pool habitats on the refuge are specifically 
managed for the conservation of listed species, and to promote habitat 
for migratory birds and waterfowl.
    The Sacramento National Wildlife Refuge contains the last remnants 
of the widespread Colusa Plains vegetation that once covered the entire 
Colusa Basin (Silveira 2000). Vernal pool habitats within the area have 
become greatly fragmented and isolated from other habitats in the 
region due to land conversion to agriculture. This unit is important to 
maintain opportunities for vernal pool fairy shrimp dispersal between 
units to the north, over 50 km (31 mi) distant, and those to the south, 
over 110 km (68 mi) distant. Without this unit, vernal pool fairy 
shrimp occurrences to the north and south would be more than 160 km 
(100 mi) distant from one another, a distance at which genetic evidence 
indicates they are effectively isolated (Fugate 1992, 1998).
    The boundaries of the unit were delineated to include the 
interconnected pools, swales, and associated uplands mapped by Holland 
(1998) and identified by the Service (Silveira 2000) that contribute to 
the filling and drying of the vernal pools where vernal pool fairy 
shrimp occur, and which maintain suitable periods of pool inundation, 
water quality, and soil moisture for vernal pool fairy shrimp hatching, 
growth, reproduction, and dispersal.
    This unit is primarily located on the Sacramento National Wildlife 
Refuge (5,126 ha (12,816 ac)). Any additional lands within this unit 
are privately owned. This unit overlaps with Unit 6 for Greene's 
tuctoria, Unit 3 for hairy Orcutt grass, Unit 3 for Hoover's spurge, 
and Unit 2 for Conservancy fairy shrimp. Other important vernal pool 
and associated upland species found in the unit include pappose 
spikeweed (Hemizonia parryi ssp. rudis), Fremont's goldfields 
(Lasthenia fremontii), alkali goldfields (Lasthenia platycarpha), 
Scribe's popcorn flower (Plagiobothrys scriptus), Hoover's downingia 
(Downingia bella), folded downingia (Downingia ornatissima var. 
ornatissima), Heckard's peppergrass (Lepidium latipes var. heckardii), 
heartscale (Atriplex cordulata), brittlescale (Atriplex depressa), San 
Joaquin spearscale (Atriplex joaquiniana), Ferris' milkvetch 
(Astragalus tender var. farrisiae), spike-primrose (Boisduvalia 
stricta), sessile mousetail (Myosurus sessilis), and palmate-bracted 
bird's beak (Cordylanthus palmatus).

Unit 11, Beale Unit, Yuba and Placer Counties (2,853 ha (7,049 ac))

    We propose the Beale Unit as essential for the conservation of 
vernal pool fairy shrimp because it contains large, relatively 
undisturbed vernal pool grassland habitats and a diversity of vernal 
pool habitat types supporting vernal pool fairy shrimp (CNDDB 2001, 
Jones and Stokes 1997b, Jones and Stokes 2002, Platenkamp 1998). Vernal 
pool fairy shrimp within this unit are found throughout several large 
vernal pool complexes. These complexes occur on four major geologic 
formations: the Modesto Formation; the Riverbank Formation; the Laguna 
Formation; and the Mehrten Formation (Platenkamp 1998). These habitats 
provide the hydrological characteristics necessary for vernal pool 
fairy shrimp growth, reproduction, dispersal, and other primary 
constituent elements essential to the conservation of this species. 
Different geologic formations provide a diversity of habitats for 
vernal pool fairy shrimp primarily through their effects on pool size 
and depth (Platenkamp 1998, Helm 1998).
    This unit contains DOD land (419 ha (1,048 ac)) at Beale Air Force 
Base and BLM (3 ha (8 ac)) lands. Other lands within this unit are 
located on private property, and are threatened by agricultural 
conversion, urban expansion, and the expansion of Highway 70 and other 
transportation projects planned in the region. This unit is found east 
of Yuba City and State Highway 65, generally south of Hammonton Road 
and north of South Beale Road and 6th Street. The unit includes the 
western portion of Beale Air Force Base, west of Erle Street and 
Doolittle Drive. Other rare vernal pool species found within this unit 
include vernal pool tadpole shrimp and California linderiella.

Unit 12, Western Placer County Unit (19,387 ha (47,905 ac))

    The Western Placer Unit was identified as critical habitat for 
vernal pool fairy shrimp because it contains numerous occurrences of 
the species (CNDDB 2001). The unit boundary was drawn to include these 
occurrences and the vernal pool complexes in which they occur as mapped 
by Holland (1998) and Glazner (2001) and as visible on SPOT imagery. 
These complexes form interconnected hydrologic units of pools, swales 
and uplands that together maintain the timing and duration of 
inundation necessary for vernal pool fairy shrimp to hatch, mature, and 
reproduce. Vernal pool fairy shrimp within this unit occur in both 
Northern Hardpan and Northern Volcanic Mudflow vernal pools as 
described by Sawyer and Keeler-Wolf (1995). This unit also supports 
vernal pool fairy shrimp found in vernal pools on Exchequer soils on 
the Mehrten geologic formation, a rare type of Northern Volcanic 
Mudflow vernal pool which has been reduced to only a few acres in 
extent. The pools are relatively short lived and do not provide habitat 
for most other species of fairy shrimp (CNDDB 2001).
    This unit includes a large number of conservation areas established 
specifically to contribute to the recovery of vernal pool fairy shrimp 
partly established through conservation efforts under section 7 of the 
Act. These include the Ahart Preserve, one of the few remaining 
examples of Northern Volcanic Mudflow vernal pools in the region, as 
well as the Orchard Creek Conservation Bank. This conservation bank was 
established for the protection of vernal pool fairy shrimp and to 
compensate for the loss of thousands of acres of vernal pool grassland 
habitats throughout Placer and Sacramento counties. Additional smaller 
conservation areas in this unit are located within the cities of 
Lincoln and Roseville, and in Placer County. Approximately 20 percent 
of all mitigation areas established for the long-term protection of 
vernal pool fairy shrimp are found within this unit. Placer County is 
currently developing a HCP for the conservation of vernal pool fairy 
shrimp in this area. A WRP easement of 63 ha (157 ac) is within this 
unit.
    The Western Placer Unit contains 70 percent of the remaining vernal 
pool habitats in Placer County. TNC identified this area as one of the

[[Page 59923]]

outstanding vernal pool sites remaining in the Sacramento Valley. 
Vernal pool habitats within this unit are threatened by the development 
of large transportation projects, the development of a university and 
associated infrastructure, residential developments, gravel mining 
operations, and agricultural conversion in the western portion of 
Placer County.
    This unit generally occurs in western Placer County immediately 
north of the Sacramento County line, north of the City of Roseville and 
the City of Rocklin. The northern boundary occurs just north of the 
City of Lincoln. This unit occurs mostly west of State Highway 65. This 
unit provides habitat for sensitive vernal pool species such as Bogg's 
Lake hedge-hyssop, Red Bluff dwarf rush, western spadefoot toad, 
legenere, California linderiella, Ahart's paronychia, and dwarf 
downingia. A number of riparian species are also found in this unit in 
the vernal pool grasslands that border Coon Creek.

Unit 13, Mather Unit, Sacramento County (14,866 ha (36,733 ac))

    This unit is proposed as critical habitat for vernal pool fairy 
shrimp because it contains occurrences of the species and vernal pool 
habitats that sustain the necessary timing and length of inundation 
required for the species to hatch, mature, reproduce, disperse, and 
enter dormancy (Holland 1998, Sacramento County 1999, CNDDB 2001). 
Vernal pool fairy shrimp in this unit occur within a diversity of 
vernal pool habitats, including young or low terrace vernal pools on 
the Riverbank Formation, old or high terrace vernal pools on the Laguna 
and Arroyo Seco geologic formations, and Northern Volcanic Mudflow 
vernal pools on the Mehrten and Valley Springs geologic formations.
    This unit includes several conservation areas established by 
private entities, including the Sunrise Douglas Conservation Bank, the 
Arroyo Seco Conservation Bank, the Churchill Downs mitigation area, and 
Teichert mitigation areas. These areas were established specifically to 
contribute to the conservation of vernal pool fairy shrimp, and 
represent compensation measures for the loss of thousands of acres of 
vernal pool fairy shrimp habitat within Sacramento County. The 
continued functioning of these areas is essential to the conservation 
of vernal pool fairy shrimp and other vernal pool species. The 
boundaries of the unit were delineated to include the interconnected 
pools, swales, and associated uplands mapped by Holland (1998) that 
contribute to the filling and drying of the vernal pools where vernal 
pool fairy shrimp occur, and which maintain suitable periods of pool 
inundation, water quality, and soil moisture for vernal pool fairy 
shrimp hatching, growth, reproduction, and dispersal.
    This area supports a diversity of vernal pool species and habitats, 
and is the focus of numerous conservation planning efforts. This area 
has been identified by the Sacramento Valley Open Space Conservancy, 
the CNPS, and TNC as an excellent example of vernal pool grasslands, 
supporting a rich and diverse community of vernal pool endemic plants 
and animals within Sacramento County. This unit contains areas on 
private, county, and Federal land, including lands leased or owned by 
Sacramento County at Mather Regional Park, the former Mather Air Force 
Base, and at the county landfill. BLM owns 6 ha (18 ac) within this 
unit. Vernal pool habitats in this unit are threatened by urbanization 
from the expanding cities of Sacramento and Elk Grove. Conversion to 
intensive agriculture, particularly vineyards, is also a significant 
threat to vernal pool fairy shrimp in this unit.
    This unit includes the area to the southeast of the City of 
Sacramento in Sacramento County, east of Highway 99 and south of 
Interstate 80. The unit is generally east of Bradshaw Road, northwest 
of Grant Line Road, west of Scott Road, and includes a portion of 
Mather Field. The unit is bisected by the Folsom South Canal. This unit 
also represents Unit 8 for vernal pool tadpole shrimp, and contains 
Unit 6 for slender Orcutt grass and Unit 2 for Sacramento Orcutt grass. 
In addition to these species, this unit contains occurrences of many 
other rare, endemic vernal pool species including midvalley fairy 
shrimp (Branchinecta mesovalliensis), Bogg's Lake hedge-hyssop, western 
spadefoot toad, legenere, California linderiella, and Ahart's 
paronychia.

Unit 14, Cosumnes Unit, Sacramento County (26,600 ha (65,728 ac))

    This unit is proposed as critical habitat for vernal pool fairy 
shrimp because it supports the species (CNDDB 2001) and its habitat 
(Holland 1998, Sacramento County 1999). The unit boundary was drawn to 
include several large vernal pool complexes mapped by Holland (1998) 
and numerous individual vernal pools mapped by Sacramento County (1999) 
and visible on SPOT imagery. Together, these identified habitats 
represent some of the largest remaining vernal pool complexes in the 
Sacramento Valley that provide the necessary timing and duration of 
inundation for vernal pool fairy shrimp hatching, growth, and 
reproduction. Vernal pool fairy shrimp within this unit are found in a 
diversity of pool types, including Northern Volcanic Mudflow vernal 
pools on Pardee and Pentz soils, vernal pools occurring on low terrace 
landforms associated with San Joaquin soils, and vernal pools occurring 
on high terrace landforms associated with Redding and Corning soils. 
These pool types provide a diversity of habitats for this species. The 
large vernal pool complexes found within this unit provide relatively 
undisturbed, hydrologically intact vernal pool habitats that support 
natural vernal pool ecosystem processes and maintain suitable habitat 
conditions for vernal pool fairy shrimp.
    Many areas within this unit include actively restored and created 
vernal pools that support occurrences of vernal pool fairy shrimp 
(CNDDB 2001). This unit is also proposed as critical habitat to 
encourage that special management actions will be taken so that these 
areas continue to provide the necessary timing and length of inundation 
for vernal pool fairy shrimp survival. In many cases, the special 
management action necessary will simply be to monitor vernal pool 
hydrology to verify the success of the restoration effort.
    This unit contains a number of conservation areas established 
specifically to contribute to the conservation of vernal pool fairy 
shrimp, and to compensate for the loss of thousands of acres of vernal 
pool grassland habitats throughout the Sacramento Valley. Many areas 
within this unit are managed specifically to provide habitat for 
migratory waterfowl, this unit also provides essential habitat for 
avian species that aid in the dispersal of vernal pool fairy shrimp and 
other vernal pool crustacean cysts.
    This unit contains state and federally owned land, as well as 
private properties. Portions of the Cosumnes River Preserve occur 
within this unit. The Cosumnes River Preserve is jointly owned and 
managed by a variety of state, local, and Federal agencies including 
the BLM , CDFG, Ducks Unlimited, Inc., California Department of Water 
Resources, Sacramento Co. Dept. of Regional Parks, Open Space, and 
Recreation, TNC, and the Wildlife Conservation Board. The Cosumnes 
River Preserve encompasses and protects thousands of acres of wetlands 
and adjacent uplands, oak woodlands, and riparian forests along the 
Cosumnes River, the only undammed river on the west slope of the 
Sierra. The Cosumnes floodplain is a haven for tens of thousands of 
migratory waterfowl, songbirds, and raptors, a large portion of

[[Page 59924]]

the Central Valley's population of greater sandhill cranes, and for 
rare reptiles and mammals like the river otter and threatened giant 
garter snake. Several large, diverse, vernal pool landscapes are 
protected within this unit including the Howard Ranch and Valensin 
Ranch. The Clay Station Mitigation Bank, Laguna Creek Mitigation Bank, 
and the Borden Ranch Mitigation site are included in this unit, as well 
as a number of smaller conservation areas including the Rancho Seco 
Preserve. Land ownership and protection within the unit includes CDFG 
(630 ha (1,557 ac)), TNC (3,988 ha (9,970 ac)) lands and WRP easements 
(4 ha (11 ac)). This area has been identified by the Sacramento Valley 
Open Space Conservancy, the CNPS, and TNC as an excellent example of 
vernal pool grasslands, supporting a rich and diverse community of 
vernal pool endemic plants and animals within Sacramento County. Urban 
expansion, conversion from grazing to other agricultural practices, 
particularly vineyards, have greatly affected existing vernal pool 
habitats throughout this unit.
    This unit for vernal pool fairy shrimp occupies the area south of 
Deer Creek and Cosumnes River to just north of the Sacramento and San 
Joaquin county line near Simmerhorn Road. The eastern boundary is the 
low elevation foothills near the Amador county line. The western limit 
follows Dillard Road south to Colony Road near Herald. This unit also 
coincides with Unit 10 for vernal pool tadpole shrimp, and Unit 3 for 
Sacramento Orcutt grass. Other sensitive species found within this unit 
include Bogg's Lake hedge-hyssop, western spadefoot toad, legenere, 
California linderiella, California tiger salamander, Ahart's 
paronychia, Henderson's bent grass, Sanford's arrowhead, pincushion 
navarretia (Navarretia myersii ssp. deminuta), and dwarf downingia.

Unit 15 Vacaville Unit, Solano County (1,624 ha (4,012 ac))

    This unit is proposed as critical habitat because it contains 
vernal pool fairy shrimp within large vernal pool complexes (Holland 
1998, Solano County 2000, CNDDB 2001). This unit contains vernal pool 
fairy shrimp occurring within vernal pools and swales formed on Corning 
gravelly loam soil series, which form Northern Hardpan vernal pools 
(Sawyer and Keeler-Wolf 1995). These pool types maintain the necessary 
conditions for vernal pool fairy shrimp hatching, feeding, 
reproduction, and dispersal (CNDDB 2001).
    The Vacaville Unit supports the only examples of Northern Hardpan 
vernal pool types, including high terrace vernal pools on Corning 
soils, on the western side of the valley. These unique habitats are 
necessary to maintain the diversity of habitats in which vernal pool 
fairy shrimp are known to occur. This unit is located primarily on 
private land although the State Land Commission owns approximately (60 
ha (149 ac)) within this unit. Vernal pool habitats within this unit 
are threatened by urbanization from the expanding City of Vacaville. 
Solano County is currently developing a HCP which will address the 
conservation of vernal pool fairy shrimp in this area.
    The Vacaville Unit is situated north and northeast of the City of 
Vacaville. The eastern boundary parallels Interstate 80, the northern 
boundary parallels Midway Road, and the western boundary is near Browns 
Valley Road. This unit also provides habitat for vernal pool tadpole 
shrimp, dwarf downingia, as well as Swainson's hawks (Buteo swainsoni) 
and burrowing owls.

Unit 16, Jepson Prairie Unit, Solano County (34,910 ha (86,261 ac))

    We propose this area as critical habitat for vernal pool fairy 
shrimp because it supports numerous occurrences of the species (CNDDB 
2001) living within systems of hydrologically interconnected pools and 
swales within a matrix of surrounding uplands that together form 
hydrologically and ecologically functional vernal pool complexes. These 
features contribute to the filling and drying of the vernal pools where 
vernal pool fairy shrimp are known to occur, and maintain suitable 
periods of pool inundation, water quality, and soil moisture for vernal 
pool fairy shrimp hatching, growth and reproduction, and dispersal. 
These features have been identified and mapped by Solano County (2000), 
Holland (1998), and the Solano County Farmlands and Open Space (2000). 
The Jepson Prairie Unit encompasses the greater Jepson Prairie 
grassland area, one of the most pristine, intact vernal pool ecosystems 
remaining in California. Jepson Prairie contains large, playa-like 
vernal pools which may be over several acres in size, including the 32 
ha (80 ac) Olcott Lake. These larger pools often occur in complexes 
with smaller pools and hogwallow depressions.
    This unit includes one of only two large contiguous areas of 
habitat remaining for vernal pool fairy shrimp on the floor of the 
Central Valley. The relatively undisturbed, hydrologically intact 
condition of the Jepson Prairie increases the likelihood that it will 
continue to support natural vernal pool ecosystem processes and 
maintain suitable habitat conditions for vernal pool fairy shrimp. This 
unit also provides essential habitat for migratory waterfowl that aid 
in the dispersal of vernal pool fairy shrimp and other vernal pool 
crustacean cysts. Vernal pool fairy shrimp in the Jepson Prairie 
grassland area inhabit unique combinations of low terrace and basin rim 
landform vernal pools on a diversity of soil types.
    Jepson Prairie has long been recognized as an outstanding example 
of vernal pool ecosystems. In 1987 the National Park Service (NPS) 
named Jepson Prairie a National Natural Landmark, a designation given 
to sites that provide high quality habitat for threatened or endangered 
species. Jepson Prairie is the target of ongoing conservation planning 
efforts and active management. As part of the UC Reserve System, this 
area also provides critical research opportunities for scientists to 
study vernal pool species, including vernal pool fairy shrimp.
    The unit contains 1,038 ha (2,564 ac) owned and or administered by 
CDFG. Additional lands are owned by DOD (760 ha (1,879 ac)), California 
State Parks (15 ha (38 ac)), and the State Land Commission (109 ha (273 
ac)). NRCS holds easements or agreements protecting 436 ha (1,090 ac) 
of private land in the unit under the WRP program. TNC also holds a 
conservation easement on 623 ha (1,558 ac) in the unit. The Jepson 
Prairie Preserve is jointly managed by the Solano County Land Trust and 
the UC Reserve System. CDFG owns several ecological reserves in the 
vicinity of Jepson Prairie. This unit also contains several privately 
owned mitigation areas, and portions of Travis Air Force Base. Within 
the greater Jepson Prairie grassland area, existing vernal pools are 
threatened by agricultural conversion, landfill expansion, power plant 
construction, and utility maintenance.
    This unit is located in the southern portion of Solano County, 
southeast of Interstate 80 and the cities of Fairfield and Vacaville, 
north of Grizzly Bay and Montezuma Slough, west of the Sacramento River 
and the Solano and Sacramento County line, and south of Midway Road and 
the City of Dixon. The unit is bisected by Highway 13. This unit is 
also described as Unit 11 for vernal pool tadpole shrimp. This unit 
contains Unit 3 for Colusa grass, Unit 2 for Solano grass, Unit 3 for 
Conservancy fairy shrimp, and Unit 4 and portions of Unit 5 for Contra 
Costa goldfields. Other rare vernal pool species which occur in

[[Page 59925]]

this unit include alkali milk-vetch (Astragalus tener var. tener), 
Ferris's milk-vetch, vernal pool small scale (Atriplex persistens), 
dwarf downingia, Delta green ground beetle (Elaphrus viridus), Bogg's 
Lake hedge-hyssop, Ricksecker's water scavenger beetle (Hydrochara 
rickseckeri), California linderiella, midvalley fairy shrimp, legenere, 
and California tiger salamander.

Unit 17, Napa River Unit, Napa and Sonoma Counties (656 ha (1,621 ac))

    We propose this unit as critical habitat for vernal pool fairy 
shrimp because it contains vernal pools where vernal pool fairy shrimp 
are known to occur (CNDDB 2001). The boundaries of this unit were 
designed to include vernal pool complexes mapped by Holland (1998) and 
within the Fagan Marsh Ecological Area owned by the CDFG (420 ha (901 
ac)) that contribute to the inundation patterns, water quality, and 
soil moisture for vernal pool fairy shrimp hatching, growth and 
reproduction, and dispersal, but not necessarily every year. The 
minimum mapping unit of Holland (1998) of 16 ha (40 ac) and the 
resolution of the SPOT imagery did not allow us to identify all vernal 
pool habitat areas which provide the primary constituent elements for 
vernal pool fairy shrimp in this area. The unit boundary was designated 
to exclude tidal marsh habitats in the south, and urban and 
agricultural areas along the northern and eastern boundaries. The Napa 
River parallels the western boundary of this unit.
    This unit represents the western extent of vernal pool fairy shrimp 
range. Such isolated and peripheral populations may be essential to the 
conservation of this species because of their genetic uniqueness 
(Fugate 1992, 1998, Lessica and Allendorf 1995). This unit represents 
the only area where vernal pool fairy shrimp occur in vernal pool 
habitats forming a transition zone with tidal marshes. This unit is 
located on private and CDFG land, including the Napa-Sonoma Marsh and 
Fagan Marsh Wildlife Areas. Habitats within this unit are primarily 
threatened by urbanization from the City of Napa.
    Most of this unit is situated south and southwest of the City of 
Napa; primarily west of Highway 29, south of Highway 12, and east of 
Highway 121. This unit forms a narrow strip following the northwestern 
banks of the Napa River and extending westward along Hudeman and Schell 
sloughs. This unit is also identified as Unit 3 for Contra Costa 
goldfields. Other rare vernal pool species found in this unit include 
the alkali milk-vetch.

Unit 18, San Joaquin Unit, San Joaquin County (7,105 ha (17,557 ac))

    This unit is proposed as critical habitat for vernal pool fairy 
shrimp because it contains vernal pool habitats identified by Holland 
(1998) and San Joaquin County (1998) that support populations of vernal 
pool fairy shrimp (CNDDB 2001). This unit contains vernal pool fairy 
shrimp occurrences found within Northern Volcanic Mudflow vernal pools 
on the Laguna geologic formation, as well as high terrace pools on the 
Valley Springs geologic formation. The Northern Volcanic Mudflow vernal 
pools tend to be short-lived, and are a relatively rare habitat type 
for vernal pool fairy shrimp. This unit contains the largest vernal 
pool complex remaining in San Joaquin County and the southern 
Sacramento Valley, and contains the necessary geographic, topographic, 
and edaphic features to support vernal pool fairy shrimp occurrences 
found within this unit. San Joaquin County has completed a HCP, which 
includes measures to protect conversion of vernal pool fairy shrimp 
habitat from vernal pools grasslands to vineyards. Conversion from 
grazing to other agricultural practices have greatly reduced the 
remaining acreage of vernal pool habitats throughout this unit.
    This unit occupies the area from the Calaveras River south to Duck 
Creek. The eastern boundary extends to near Valley Springs at the 
intersection of State routes 12 and 26. The western boundary extends to 
near Tully Road east of the City of Lodi. This unit also coincides with 
Unit 14 for vernal pool tadpole shrimp. Other sensitive vernal pool 
species found within this unit include western spadefoot toad and 
California tiger salamander. All the land within this unit is privately 
owned.

Unit 19A, B, and C, Altamont Hills Unit, Contra Costa and Alameda 
counties (3,356 ha (8,292 ac))

    This unit is proposed as critical for vernal pool fairy shrimp 
because it contains vernal pool habitats mapped by Holland (1998) and 
East Bay Regional Parks District (2001) supporting vernal pool fairy 
shrimp occurrences identified by CNDDB (2001). Vernal pool fairy shrimp 
have been discovered in very small (less than 1 m (3.3 ft) in diameter) 
clear water depression pools in sandstone outcrops in the area (Eriksen 
and Belk 1999). The unit represents the only known location that 
supports vernal pool fairy shrimp within sandstone outcrop pools 
(Eriksen and Belk 1999).
    Vernal pool fairy shrimp in the Altamont Hills Unit are located 
over 60 km (40 miles) from the closest known occurrence to north in 
Solano County and to the south in Stanislaus County, and over 60 km (40 
mi) from the next occurrence to the west in San Joaquin County. These 
populations may be genetically different from other vernal populations 
because of their relative isolation (Fugate 1998).
    The unit is comprised of three subunits in the general vicinity of 
Mount Diablo and Morgan Territory Regional Park. The unit primarily 
consists of private land, with 64 ha (157 ac) owned by the state and an 
additional 288 ha (711 ac) administered by the California Department of 
Fish and Game for conservation purposes.
    This unit overlaps Unit 7 for Contra Costa goldfields. The unit 
lies north of Corral Hollow Road, west of Clifton Court Forebay, east 
of the City of Danville, southeast of Concord, and south of Antioch. It 
includes vernal pool habitat within the Altamont Hills, around the 
northern and eastern boundaries of the City of Livermore, and east of 
the Altamont Hills and west of Clifton Court Forebay. The unit includes 
Fricke Lake which supports a large population of California tiger 
salamanders.

Unit 20, Caswell Unit, Stanislaus County (302 ha (746 ac))

    This unit is proposed as critical habitat for vernal pool fairy 
shrimp because it contains vernal pools, swales, and other ephemeral 
wetlands and depressions of appropriate sizes and depths that typically 
become inundated for sufficient lengths of time necessary for vernal 
pool fairy shrimp incubation, reproduction, dispersal, feeding, and 
sheltering, but which are dry during the summer (Holland 1998, CNDDB 
2001). This unit also supports aggregations or systems of 
hydrologically interconnected pools, swales, and other ephemeral 
wetlands and depressions within a matrix of surrounding uplands that 
together form hydrologically and ecologically functional units called 
vernal pool complexes (Holland 1998). These features contribute to the 
filling and drying of the vernal pool, and maintain suitable periods of 
pool inundation, water quality, and soil moisture for vernal pool fairy 
shrimp hatching, growth and reproduction, and dispersal, but not 
necessarily every year. This unit includes vernal pool complexes mapped 
by Holland (1998) where vernal pool fairy shrimp have been documented 
by CNDDB (2001).
    This unit is located within the San Joaquin River National Wildlife 
Refuge

[[Page 59926]]

and efforts to restore vernal pool habitats are currently underway. 
Additional restoration designed to enhance habitat for riparian 
species, as well as migratory birds and waterfowl, is also being 
conducted. The San Joaquin River National Wildlife Refuge is the 
primary wintering site of 98 percent of the Aleutian Canada geese that 
winter in the Central Valley (October-April), and it is a major 
wintering and migration area for lesser and greater sandhill cranes, 
cackling Canada geese, and white-fronted geese. These migratory birds 
act as important dispersal agents for vernal pool fairy shrimp. Lands 
within this unit form a mosaic of riparian habitat, wetlands, and 
grasslands.
    This unit is over 75 km (47 mi) from the nearest unit to the north. 
Such isolated populations may have genetic characteristics essential to 
overall long-term conservation of the species (i.e. they may be 
genetically different than more central populations) (Fugate 1992, 
1998). This unit may be threatened by agricultural development, oil and 
natural gas exploration and development, and conversion from grazing to 
other agricultural practices. Water management practices may also 
threaten vernal pool fairy shrimp in this unit if natural vernal pool 
hydrology is altered.
    This unit is situated west of the City of Modesto and east and 
southeast of the confluence of the San Joaquin and Stanislaus rivers. 
Caswell Memorial State Park lies just north of this unit and is not 
included. The San Joaquin River forms the western boundary of the unit. 
The unit is bisected by the Hetch Hetchy Aqueduct, State Highway 132, 
and the Tuolumne River. Roughly the northern one-third of this unit 
overlaps with Unit 5 for Conservancy fairy shrimp. It is also contains 
California linderiella and California tiger salamander occurrences, in 
addition to a number of rare non-vernal pool species, including the 
federally listed endangered riparian wood rat and riparian brush 
rabbit.

Unit 21, Stanislaus Unit, Stanislaus and Merced Counties (25,317 ha 
(62,557 ac))

    This area is proposed as critical habitat for vernal pool fairy 
shrimp because it contains occurrences of the species within large, 
relatively intact, and contiguous vernal pool complexes ranging from 
the floor of the valley to the low elevation foothills (Holland 1998, 
CNDDB 2001). These areas are essential to the conservation of vernal 
pool fairy shrimp because they provide relatively undisturbed, 
hydrologically intact vernal pool habitats that will likely continue to 
support natural vernal pool ecosystem processes and maintain suitable 
habitat conditions for vernal pool fairy shrimp. This unit contains 
vernal pool fairy shrimp living within hardpan pools that occur on 
soils of alluvial fans and terraces forming numerous small pools and 
swales on mima mound topography. Soils supporting these vernal pools 
are typically older than those of the alluvial terraces in the 
Sacramento area. These pools provide the necessary timing and length of 
inundation for vernal pool fairy shrimp to complete their life cycle, 
reproduce, and disperse.
    The Stanislaus Unit is in the northern portion of the chain of 
vernal pools that runs through the southern Sierra Nevada foothills, 
within the Southern Sierra Foothill vernal pool region described by 
Keeler-Wolf et al. (1998). This vernal pool region contains 35 percent 
of all remaining vernal pool habitat in the Central Valley, and is 
extremely important to the conservation of vernal pool fairy shrimp and 
other vernal pool species. Land ownership within this unit includes the 
BLM (7 ha (17 ac)) and the California State Parks (25 ha (61 ac)). The 
well-known Hickman pools in Stanislaus County are located within this 
unit. Not only does the Hickman pool complex contain one of the largest 
vernal lakes in California at more than 121 ha (300 ac), but it also 
exhibits tremendous biodiversity, including one of the largest 
concentrations of imperiled amphibians (Medeiros 2000). However, the 
watershed containing the Hickman vernal pools has been breached by 
hundreds of acres of orchards that have been planted upstream. While 
most of the watershed has been managed over the years in a trust of the 
Fred Robinson family, the integrity of the vernal pool ecosystem is 
threatened by agricultural development and potential biocide pollution 
(Medeiros 2000).
    The Stanislaus Unit is located in the southeast corner of 
Stanislaus County and the northeast corner of Merced County. It lies 
between the Tuolumne River and the Merced River. The Mariposa County 
line is located east of the unit. Turlock Lake and Dawson Lake are 
adjacent to the northern boundary. County Road J9 and the High Line 
Canal are west of the unit. This unit coincides with vernal pool 
tadpole shrimp Unit 16. It includes succulent owl's-clover Unit 3, 
hairy Orcutt grass Unit 5, Colusa grass Unit 6, and Hoover's spurge 
Unit 5. Other sensitive vernal pool species found within this unit 
include western spadefoot toad, dwarf downingia, California 
linderiella, California tiger salamander, and Hartweg's golden sunburst 
(Pseudobahia bahiifloia).

Unit 22, Merced Unit, Merced and Mariposa Counties (44,106 ha (108,984 
ac)

    We propose this unit as critical habitat for vernal pool fairy 
shrimp because it encompasses the largest block of pristine, high 
density vernal pool grasslands supporting the species remaining in 
California (Holland 1998, Vollmar 1999, CNDDB 2001). These habitats 
provide the primary constituent elements essential for vernal pool 
fairy shrimp. There are more documented occurrences of vernal pool 
fairy shrimp in this unit than any other area throughout the species 
range (CNDDB 2001). Almost 15 percent of all remaining vernal pool 
habitats in the Central Valley are located within this unit (Holland 
1998).
    The Merced Unit is located midway in a chain of vernal pool 
complexes that straddles the valley floor and the foothills of the 
southern Sierra Nevada. This unit helps to maintain connectivity 
between vernal pool fairy shrimp habitats on the valley floor and 
habitats to the north and south of the Merced Unit. Genetic analyses of 
vernal pool tadpole shrimp revealed that occurrences in this unit were 
genetically different from other sampled occurrences in California, and 
that this area had likely been isolated from other vernal pool habitats 
for a significant period of time (King 1996). Given that vernal pool 
fairy shrimp and vernal pool tadpole shrimp are dispersed in similar 
ways, it is reasonable to assume that vernal pool fairy shrimp 
occurrences in this area are also isolated from other occurrences 
throughout its range.
    This unit contains habitat for three listed branchiopods, six 
listed plants, and a suite of sensitive species. Forty percent of 
vernal pool habitats in the Southern Sierra Foothill vernal pool region 
are found within this unit. The integrity of the vernal pool complexes 
in eastern Merced is seriously threatened by irrigated agriculture, 
upland housing development, and the proposed UC Merced Campus and 
associated development. Construction of facilities to educate and serve 
twenty-five thousand UC students as well as faculty, staff, and their 
families within the vernal pool complexes in eastern Merced County 
could have a major impact on vernal pool fairy shrimp occurrences. 
However, the recent draft biological opinion for the UC Merced campus 
and community developed environmental parameters which should reduce 
impacts to vernal pool habitats. Indirect and cumulative impacts of the

[[Page 59927]]

proposed 1,673 ha (4,133 ac) campus and associated community may be 
minimized with the creation of a 2,036 ha (5,030 ac) preserve intended 
to protect sensitive vernal pool habitat, to be purchased with money 
donated by the Packard Foundation.
    A majority of vernal pool habitat in the Merced Unit is in Merced 
County. The eastern edge of the unit overlaps into Mariposa County. 
Bear Creek flows along the southern boundary of the unit, crossing 
through it in several locations. The City of Merced is south of the 
unit, Bear Reservoir is southeast of the unit and the Castle Airport is 
located outside of the southwest boundary. The northern boundary 
parallels the Merced River. The entire unit is located east of Highway 
99. Land ownership within the unit includes approximately 3 ha (8 ac) 
of BLM, and 10 ha (26 ac) of California State Parks. TNC has a total of 
4,513 ha (11,283 ac) of conservation easements within this unit. The 
Merced Unit coincides with vernal pool tadpole shrimp Unit 13, 
succulent owl's-clover Unit 4, San Joaquin Valley Orcutt grass Unit 2, 
Colusa grass Unit 7, and Conservancy fairy shrimp Unit 6. Other 
sensitive vernal pool species found within this unit include the 
California tiger salamander, shining navarretia (Navarretia 
nigelliforms ssp radians), dwarf downingia, Bogg's Lake hedge-hyssop, 
western spadefoot toad, and California linderiella.

Unit 23, Grassland Ecological Unit, Merced County (55,910 ha (138,153 
ac))

    We propose this unit as critical based upon the presence of vernal 
pools and vernal pool fairy shrimp. This unit supports numerous 
occurrences of vernal pool fairy shrimp within a diversity of vernal 
pools supported by a number of different soil types, including Delhi-
Dello-Himar, Solano-Caypay-Willows, Rossi-Waukena, and Lewis-Landlow 
soils (CNDDB 2001, USDA 2001). This diversity of soils creates a wide 
range of vernal pool shapes, sizes, and physical characteristics which 
provide the essential timing, frequency, and length of inundation 
necessary for the conservation of the species. This unit contains 
numerous large, intact vernal pool grasslands, and is one of only two 
areas on the floor of the Central Valley that provide expansive areas 
of vernal pool complexes within which vernal pool fairy shrimp can 
hatch, mature, and reproduce. These areas will likely continue to 
support natural vernal pool ecosystem processes and maintain suitable 
habitat conditions for vernal pool fairy shrimp. This unit also 
provides habitat for migratory waterfowl that aid in the dispersal of 
vernal pool fairy shrimp and other vernal pool crustacean cysts. This 
is the only area where all four vernal pool crustaceans addressed in 
this proposed rule are known to co-occur.
    The Grasslands Unit includes Kesterson, San Luis, and Merced 
National Wildlife Refuges, as well as several Federal and State 
conservation easement areas, lands owned by the California State Parks 
and Wildlife Areas, and private lands. Land ownership within the unit 
includes the Service (13,943 ha (34,452 ac)), CDFG lands (1703 ha 
(4,257 ac)), California State Parks (1,357 ha (3,392 ac)), CDFG 
administered lands (1,052 ha (2,631 ac)) and WRP conservation easements 
(54 ha (134 ac)). All other lands within this unit are privately owned. 
Together, these areas are known as the Grasslands Ecological Area. This 
area supports diverse wetland habitats including seasonally flooded 
marshlands, semi-permanent marsh, riparian habitat, wet meadows, vernal 
pools, native uplands, pastures, and native grasslands. Wetlands within 
this area, including seasonal marsh and open water habitats, constitute 
30 percent of the remaining wetlands in California's Central Valley and 
are extremely important to Pacific Flyway waterfowl populations. Over 
60 million duck use-days and 3 million goose use-days occur annually in 
this unit. This habitat also supports a diversity of other migratory 
birds, including raptors, shorebirds, wading birds, and other wildlife 
species.
    This unit contains over 50 percent of the remaining vernal pool 
habitats within the San Joaquin Valley identified by Holland (1998). 
This area is an important portion of the geographic distribution of 
vernal pool fairy shrimp within the San Joaquin Valley. Threats to 
vernal pool fairy shrimp within this unit include conversion to 
agriculture, changes in hydrology, invasion by aggressive plants, and 
certain wetland management practices.
    The unit lies north of the City of Los Banos, southwest of the City 
of Merced, and is bisected by the San Joaquin River. This unit also 
represents Unit 24 for tadpole shrimp. The western half of this unit 
also represents Unit 2 for longhorn fairy shrimp and the eastern half 
represents Unit 8 for Colusa grass, Unit 8 for Hoover's spurge, and 
Unit 7 for Conservancy fairy shrimp. In addition to the species 
mentioned above, other sensitive vernal pool species occur within the 
unit including Hispid's bird beak, Sanford's arrowhead, heartscale, 
brittlescale, vernal pool smallscale, delta button celery, alkali milk-
vetch, California tiger salamander, western spadefoot toad, and 
California linderiella.

Unit 24A and B, Madera Unit, Madera and Fresno Counties (17,232 ha 
(42,579 ac))

    The Madera Unit is proposed as critical habitat for vernal pool 
fairy shrimp because it contains occurrences of the species living 
within hardpan vernal pool complexes composed of numerous small pools 
and swales on mima mound topography (Holland 1998, Keeler-Wolf et al. 
1998, CNDDB 2001). These vernal pools occur on alluvial fans and 
terraces and provide the necessary timing and duration of inundation 
essential to the conservation of vernal pool fairy shrimp. South of 
this unit in Fresno County these pools become less common as the soils 
that support them are less widespread (Keeler-Wolf et al. 1998).
    Located in western Madera County, this unit is located between the 
Fresno River and San Joaquin River. Land ownership within this unit 
includes 0.4 ha (1 ac) of CDFG lands. All other land within this unit 
is privately owned. All vernal pools in this unit are located east of 
Highway 99 and the Atchison, Topeka, and Santa Fe Railroad, extending 
east toward the low elevation foothill region of the Sierra Nevada. 
State Route 145 bisects the unit. The Madera Unit encompasses San 
Joaquin Valley Orcutt grass Unit 5a, hairy Orcutt grass Unit 7, and 
succulent owl's-clover Unit 7a. Other sensitive vernal pool species 
found within this unit include California linderiella, California tiger 
salamander, and western spadefoot toad.
    This unit consists of two subunits. Subunit A contains vernal pool 
habitats south of Millerton Lake. The western boundary of this unit is 
bordered by the San Joaquin River. Gordon Road cuts through the 
southernmost tip of the unit. Owens Mountain and Table Mountain 
Rancheria are located east of the Unit. The Friant Kern Canal crosses 
through the unit in a southeasterly direction. Subunit B is located 
mostly west of State Route 41 along Little Dry Creek and Cottonwood 
Creek.

Unit 25, Kennedy Table Unit, Madera County (994 ha (2,456 ac))

    We propose this unit as critical habitat because it contains vernal 
pools and vernal pool fairy shrimp (Holland 1998, CNDDB 2001). Vernal 
pool fairy shrimp within this unit live within rare Northern Basalt 
Flow vernal pool complexes that provide the necessary topographic and 
edaphic conditions essential to the conservation of the species. 
Northern Basalt Flow vernal

[[Page 59928]]

pools within this unit are perched on narrow, sinuous basalt mesas 
above the surrounding low-lying terrain, and typically contain small, 
irregularly clustered pools with ``flashy hydrology'' (pools fill and 
dry quickly) (Keeler-Wolf et al. 1998). These pool types provide the 
necessary timing and length of inundation for vernal pool fairy shrimp 
to hatch, mature, and reproduce, but do not stay inundated long enough 
to allow the invasion of aquatic species (CNDDB 2001). The Kennedy 
Table Unit is over 50 km (31 mi) from the next closest unit to the 
south and over 65 km (40 mi) from the nearest unit to the north. Such 
peripheral populations may have genetic characteristics essential to 
overall long-term conservation of the species (i.e., they may be 
genetically different than more central populations) (Fugate 1998).
    This unit is located north and west of the Fresno County line on 
Kennedy Table in Madera County. It is northeast of Millerton Lake, and 
the San Joaquin River flows east and south of it. Land ownership within 
this unit includes 65 ha (161 ac) of BLM lands. All other land within 
this unit is privately owned. This unit coincides with vernal pool 
tadpole shrimp Unit 19, succulent owl's-clover Unit 8A and B, San 
Joaquin Valley Orcutt grass units 5B and 6A, and hairy Orcutt grass 
Unit 10. In addition to these federally listed species other sensitive 
vernal pool species found within this unit include California 
linderiella, California tiger salamander, and the western spadefoot 
toad. In addition to these, the federally endangered Hartwig's golden 
sunburst also occurs within this unit.

Unit 26A, B, and C, Cross Creek Unit, Tulare and Kings Counties (3,193 
ha (7,891 ac))

    This unit is proposed as critical for vernal pool fairy shrimp 
because it contains vernal pools that support occurrences of the 
species (Holland 1998, CNDDB 2001). Vernal pool fairy shrimp in this 
area occur in vernal pools formed on Lewis and Youd soils (USDA 2001). 
This area represents the southern extent of vernal pool fairy shrimp 
range along the eastern margin of the Central Valley, and is the 
largest contiguous vernal pool habitat in this region (Holland 1998, 
CNDDB 2001).
    This unit contains the CDFG's Sequoia Field and Stone Corral 
Ecological Reserves in Tulare County. These reserves are one of the few 
vernal pool conservation areas in the eastern portion of the San 
Joaquin Valley, and they have been the focus of several monitoring and 
management efforts. Land ownership within this unit includes 348 ha 
(861 ac) of CDFG lands. All other land within this unit is privately 
owned. TNC, Tulare County, and the Sierra Los Tulares Land Trust have 
identified this area as one of the best remaining examples of vernal 
pool habitats in the region. Much of the vernal pool habitat within 
Tulare County has been severely degraded and converted. The conversion 
of habitat adjacent to this unit to urbanized areas, orchards, and 
other forms of irrigated agriculture continues to threaten the long-
term viability of the vernal pools within this unit.
    This unit is comprised of three subunits. Subunit A is located in 
northwest Tulare County and contains vernal pool habitat located west 
of Seville. The Friant Kern Canal is north of the unit and the 
Cottonwood Creek Levee is south of the unit. Road 140 runs west of the 
unit. Subunit B contains vernal pools in northeastern Kings County and 
northwestern Tulare County. Highway 99 and St. Johns River cut through 
the unit in a southeasterly direction. Cross Creek and Cottonwood Creek 
cut through the unit in a southwesterly direction. Road 112 is east of 
the unit and the Lakeland Canal is west of the unit. The towns of 
Goshen and Visalia are south of the unit and Traver and London are 
north of the unit. Subunit C is known as Sequoia Field Unit and is 
located in northwestern Tulare County. This unit is south of County 
Road J36. Road 112 crosses through the western edge of the unit, Avenue 
352 crosses through the southern edge, and State Route 63 crosses 
through the eastern edge. The Cross Creek Unit coincides with vernal 
pool tadpole shrimp Unit 20 and contains portions of San Joaquin Valley 
Orcutt grass Unit 8 and Hoover's spurge Unit 9. Other sensitive vernal 
pool species found within this unit include the California tiger 
salamander, spiny-sepaled button-celery, and western spadefoot toad.

Unit 27A and B, Pixley Unit, Tulare County (7,842 ha) 19,377 ac))

    This unit is proposed for vernal pool fairy shrimp because it 
contains the largest contiguous area of habitat for the species in the 
southern portion of the San Joaquin Valley, and supports vernal pools 
that provide the necessary timing and length of inundation essential to 
the conservation of vernal pool fairy shrimp (Holland 1998, CNDDB 
2001). Vernal pool fairy shrimp in this area occur within Northern 
Claypan vernal pools that tend to be alkaline and larger than other 
vernal pool fairy shrimp habitats, such as those found on the eastern 
margin of the San Joaquin Valley.
    This unit contains wintering areas for migratory waterfowl, 
shorebirds, marsh, and waterbirds in the southern San Joaquin Valley, 
and include natural valley grasslands and developed marsh habitats 
within the Pixley National Wildlife Refuge complex (2,742 ha (6, 776 
ac)). Other ownership within this unit include CDFG (490 ha (1,210 ac)) 
and TNC lands (1,309 ha (3,274 ac)). All other lands within this unit 
are privately owned. These habitats are important for migratory 
waterfowl that aid in the dispersal of vernal pool fairy shrimp and 
other vernal pool crustacean cysts. This unit represents one of only 
three areas designated for vernal pool fairy shrimp in the San Joaquin 
Valley vernal pool region described by Keeler-Wolf et al. (1998). The 
refuge also provides habitat for the endangered San Joaquin kit fox and 
the blunt-nosed leopard lizard. Vernal pool fairy shrimp within this 
unit are threatened by agricultural development, oil and natural gas 
exploration and development, subdivision of ranches and land grants, 
urban expansion, and conversion from grazing to other agricultural 
practices.
    This unit consists of two subunits that lie south of the Cities of 
Hanford and Lemoore, north of the City of Wasco, and east of the City 
of the Tulare. In addition to vernal pool fairy shrimp, western 
spadefoot toad and California tiger salamander are present within this 
unit.

Unit 28, San Benito County Unit, San Benito and Monterey Counties 
(48,125 ha (118,915 ac))

    The San Benito County unit is located in the southwestern portion 
of San Benito County and the eastern-most portion of Monterey County. 
This unit consists of a distinct collection of seasonally flooded 
wetlands west of the Great Central Valley, and overlaps a portion of 
the Central Coast vernal pool region that has been delineated by the 
CDFG (Keeler-Wolf et al. 1998). The proposed critical habitat unit 
contains a minimum of 13 vernal pool complexes that are 7 to 144 ha (17 
to 356 ac) in size, and also includes a number of unmapped vernal pools 
or pool complexes that are less than 4 ha (10 ac) in size. Focused 
surveys for vernal pool fairy shrimp have not been conducted within the 
proposed critical habitat unit, and it is therefore likely that this 
species is present in many, if not most, of the vernal pool complexes 
that have not been censussed due to habitat similarity to where the 
occurrences have been documented. This conclusion is supported by the 
fact that two-thirds of vernal pool fairy shrimp occurrences

[[Page 59929]]

that have been documented within the critical habitat unit were not 
located within large vernal pool complexes, but were instead found in 
smaller, unmapped vernal pools. Land ownership within this unit 
includes BLM (1,581 ha (3,906 ac)) and State Land Commission (2 ha (5 
ac)). All other lands within this unit are privately owned. The 
critical habitat unit perimeter is defined by the presence of low slope 
areas within watershed boundaries that are known to contain vernal pool 
fairy shrimp occurrences and vernal pool habitats. Conservation of 
vernal pools in the San Benito County unit is necessary to maintain and 
restore occurrences of vernal pool fairy shrimp that are disjunct from 
other listed fairy shrimp localities in the Great Central Valley.

Unit 29A, B, and C, Central Coastal Ranges Unit, Monterey and San Luis 
Obispo Counties (41,054 ha (101,444 ac))

    The Central Coastal Ranges Unit includes three subunits that occur 
in Monterey and San Luis Obispo counties. The three subunits include 
areas at or adjacent to Fort Hunter Liggett, Camp Roberts, and the city 
of Paso Robles. The vast majority of the Fort Hunter Liggett subunit 
overlaps the military reservation, and also includes a small portion of 
privately owned land east of the military base. Land ownership within 
this unit includes DOD (20,585 ha (50,866 ac)) and BLM (1 ha (2 ac)). 
All other lands within this unit are privately owned. Intensive surveys 
on Fort Hunter Liggett have documented the occurrence of listed fairy 
shrimp in a minimum of 65 different pools within the base boundary 
(Fort Hunter Liggitt 2000). Several additional pools in restricted 
access areas on the base have not been surveyed, and some of these are 
also likely to possess listed fairy shrimp. The majority of the Camp 
Roberts subunit includes land within that military base boundary, and 
includes a limited amount of privately owned land north and southeast 
of the military base. Surveys on Camp Roberts have documented the 
presence of vernal pool fairy shrimp at 61 sites (Jones and Stokes 
1997a). One hundred and nineteen additional sites were also found to 
possess unidentified juvenile fairy shrimp, and the inability to 
document the presence of other fairy shrimp taxa on the base suggests 
that these pools are therefore likely to contain listed species. The 
Paso Robles subunit consists of a polygon that is 3.2 to 24 km (2 to 15 
mi) northeast of the city boundary. A limited number of surveys for 
fairy shrimp within the subunit have been conducted by California 
Department of Transportation staff along State Highway 46. These 
surveys have documented the occurrence of vernal pool fairy shrimp 
within the subunit (Mitch Dallas, California Department of 
Transportation, pers. comm.). The Paso Robles subunit possesses several 
large vernal pool complexes that are 42,314 ha (105,776 ac) in size. 
The discovery of vernal pool fairy shrimp in the area 6 km (4 mi) east 
of the city suggests that the species is likely to be widely dispersed 
in remnant vernal pools or complexes that still exist within the 
critical habitat subunit. The Fort Hunter Liggett subunit occurs within 
the Central Coast vernal pool region that has been delineated by the 
CDFG (Keeler-Wolf et al. 1998), and the Camp Roberts and Paso Robles 
subunits occur within the Carrizo vernal pool region. The subunit 
perimeters are defined by the presence of low slope areas within 
watershed boundaries that are known to contain vernal pool fairy shrimp 
and vernal pool habitats. Conservation of vernal pools in the region is 
necessary to stabilize and recover remnant populations of vernal pool 
fairy shrimp in the central coastal county area of southern California.

Unit 30, Carrizo Plain Unit, San Luis Obispo County (10,466 ha (25,862 
ac))

    This unit is proposed as critical for vernal pool fairy shrimp 
because it contains vernal pool habitats identified by Holland (2002) 
and that support occurrences of vernal pool fairy shrimp (CNDDB 2001). 
Vernal pool fairy shrimp found in the Carrizo Plain live within 
Northern Claypan vernal pools (Sawyer and Keeler-Wolf 1995) which occur 
in numerous shallow alkaline depressions within a Valley Saltbush Scrub 
matrix. These pools provide all of the primary constituent elements 
essential for the conservation of vernal pool fairy shrimp, as well as 
the edaphic and geologic features necessary to maintain the hydrology 
of the vernal pool complexes.
    Many vernal pools in the region are adjacent to the 1,214 ha (3,000 
ac) Soda Lake, the largest alkali wetland in central and southern 
California, which provides a winter haven for thousands of migratory 
birds. Vernal pool fairy shrimp in the Carrizo Plain Unit are located 
235 km (146 mi) southeast of the closest known occurrences at Kesterson 
National Wildlife Refuge in Merced County. Such isolated and peripheral 
populations may have genetic characteristics that are different than 
more central populations, and may be important for conservation (Lesica 
and Allendorf 1995, Fugate 1998). The Carrizo Plain Unit is the only 
area where vernal pool fairy shrimp are known from saline salt brush 
scrub vernal pool habitats.
    The Carrizo Plain contains examples of native bunch grass, needle 
grass, and blue grass grasslands, as well as populations of federally 
listed San Joaquin kit fox, blunt nosed leopard lizard, giant kangaroo 
rat, California jewel flower, Lost Hills salt brush, Kern mallow and 
San Joaquin wooly threads. Most of the habitat within this unit is part 
of the Carrizo Plain National Monument, which is administered by the 
BLM, TNC, and the CDFG. The BLM lands within the unit total 
approximately 6,220 ha (15,549 ac) and the CDFG lands total 
approximately 93 ha (233 ac). Other vernal pool habitats in the unit 
are located on private land.
    This unit includes vernal pool habitat in the interior basin of the 
Carrizo Plain. It encompasses California Valley and Soda Lake. State 
Highway 58 is located north of the unit. Most of the habitat is east of 
Soda Lake Road, however, Soda Lake Road crosses through the western 
edge of the unit in several areas. To the east, the unit is bordered by 
the San Andreas Rift Zone. This unit coincides with longhorn fairy 
shrimp Unit 3.

Unit 31, Lake Cachuma Area, Santa Barbara County (8,399 ha (20,754 ac))

    The Lake Cachuma critical habitat unit is located within a 16 km 
(10 mi) radius of the northwestern portion of Lake Cachuma in central 
Santa Barbara County. The unit boundary has been delineated to include 
hydrologic units that contain vernal pool fairy shrimp and vernal pool 
habitats. Vernal pool complexes within the unit vary in size from 16 to 
81 ha (40 to 199 ac). Surveys for fairy shrimp species have rarely been 
conducted within the unit. A portion of the unit overlaps the Santa 
Barbara vernal pool region that has been delineated by the CDFG 
(Keeler-Wolf et al. 1998). The Lake Cachuma unit is essential for the 
conservation of vernal pool fairy shrimp because it contains seasonally 
flooded aquatic environments that contain markedly disjunct species 
occurrences. Landownership within this unit includes U.S. Forest 
Service (USFS) (2,199 ha (5,434 ac)) and BLM (37 ha (92 ac)). Other 
land within this unit is privately owned.

Unit 32, Ventura County Unit, Ventura County (18,831 ha (46,531 ac))

    The Ventura County unit is located in the north-central portion of 
Ventura County. All the lands within this unit are owned by the USFS. 
Vernal pool

[[Page 59930]]

fairy shrimp and Conservancy fairy shrimp are known to co-occur at 
relatively high elevation ([tilde]1700 m (5500 ft)) forested sites 
within the Los Padres National Forest. Almost all of the known 
localities that possess these two species within the state of 
California exist at much lower elevations in grassland habitats. The 
critical habitat perimeter consists of an area that is known to contain 
vernal pool and Conservancy fairy shrimp occurrences and isolated pools 
that provide habitat for the two species. Fairy shrimp surveys have 
rarely been conducted in the proposed critical habitat unit. The 
Ventura County unit is essential for the conservation of vernal pool 
fairy shrimp because it contains ephemeral aquatic environments that 
are rarely associated with fairy shrimp, and the occupied sites 
represent markedly disjunct occurrences for the species.

Unit 33A, B, and C San Jacinto-Hemet Unit, Riverside County (2,319 ha 
(5,730 ac)).

    This unit lies in the southern portion of the San Jacinto Valley 
and contains two primary subunits (San Jacinto and Hemet), the latter 
of which is itself divided into two smaller subunits (33B and 33C). 
Unit 33 consists of the remnant alkali playa associated with the San 
Jacinto River (subunit A) and the upper Salt Creek drainage (subunits B 
and C). Large portions of the alkali willow soils associated with these 
watercourses have been historically altered by drainage projects and 
agriculture resulting in the degradation or destruction of vernal pool 
habitat. The unit consists of areas where vernal pool fairy shrimp 
remain extant and/or where essential hydrology and alkali soils are 
intact supporting vernal pool and alkali playa habitat. All the lands 
within this unit are privately owned.
    The San Jacinto primary subunit (subunit 33A) consists of lands 
along the San Jacinto River floodplain from the Ramona Expressway 
westward past Interstate 215 to the upper reaches of the northern 
portion of Railroad Canyon Reservoir. The lands delimited by this 
subunit represent the largest remaining contiguous alkali playa/vernal 
pool habitat within the historic range of vernal pool fairy shrimp in 
southern California. The subunit contains multiple extant vernal pools 
and complexes scattered along the river floodplain with intact water 
circulation processes and alkaline soil substrates preferred by vernal 
pool fairy shrimp.
    A presence/absence survey for federally listed fairy shrimp was 
conducted in a portion of the pools in this subunit in the spring of 
2000. No listed fairy shrimp were detected. However, not all vernal 
pool basins filled in the spring of 2000, and of those that did, not 
all retained water throughout the sample period. Additionally, no 
survey for fairy shrimp cysts (dry season survey) has been conducted. 
Therefore, the survey effort is inconclusive for the presence of listed 
fairy shrimp species. However, the common versatile fairy shrimp 
(Branchinecta lindahli) was detected in these pools (Bomkamp 2000). 
Further, the threatened spreading navarretia (Navarretia fossalis), the 
threatened thread-leaved brodiaea (Brodiaea filifolia), and the 
endangered San Jacinto Valley crownscale (Atriplex coronatum var. 
notatior) have also been documented within this subunit. These species 
are all associated with vernal pool and alkali playa habitats.
    Even though the presence of vernal pool fairy shrimp in the San 
Jacinto River floodplain has not been established, the vernal pool 
alkali playa habitat of subunit 33A is considered to be essential for 
the conservation of vernal pool fairy shrimp in southern California. As 
previously indicated, these pools contain the largest remaining 
contiguous alkali playa/vernal pool habitat within the historic range 
of vernal pool fairy shrimp in southern California, as well as 
appropriate water circulation patterns, alkali soils, and relatively 
close proximity to the occupied Hemet primary subunit.
    The Hemet primary subunit (subunits 33B and 33C) include the west 
Hemet vernal pool complex along Florida Avenue (subunit 33B), as well 
as a small area east of Warren Road and north of Tres Cerritos (subunit 
33C). Vernal pool fairy shrimp have been documented in the southwestern 
portion of the vernal pool complex. The remainder of this proposed 
subunit contains lands within the watershed of the occupied pool 
complex and other vernal pools in the basin. Lands within the watershed 
have been included to maintain the integrity of the surface flow and 
water quality to the pool complexes and playa overall.
    In addition to vernal pool fairy shrimp, several federally listed 
plants including the threatened spreading navarretia, the threatened 
thread-leaved brodiaea, the endangered California Orcutt grass 
(Orcuttia californica), and the endangered San Jacinto Valley 
crownscale have also been documented within this subunit. These species 
are all associated with vernal pool and alkali playa habitats.
    Unit 33 includes areas where vernal pool fairy shrimp are extant 
and recovery value for this species is high because of appropriate 
hydrology, soils and alkali vernal pool habitat. The alkali soils and 
their associated hydrology in the unit are essential to the 
conservation of vernal pool fairy shrimp in southern California 
(Service 1998).

Unit 34, Santa Rosa Plateau Unit, Riverside County (1,718 ha (4,246 
ac))

    The Santa Rosa Plateau critical habitat unit is on a large mesa 
made of basaltic and granitic substrates within the Santa Rosa Plateau 
Ecological Reserve. The unit contains one of the largest remaining 
vernal pool complexes in southern Riverside County and includes a 
series of large and small pools in which several sensitive or federally 
listed fairy shrimp have been documented. These include the vernal pool 
fairy shrimp (Angelos 1998), the endangered Riverside fairy shrimp 
(Streptocephalus woottoni) (Service 2001), and the Santa Rosa fairy 
shrimp (Linderiella santarosae) (Angelos 1998). Additionally, the 
federally endangered California Orcutt grass is documented from the 
pool complex (Service 1998). This unit was designated as critical 
habitat for the Riverside fairy shrimp on May 30, 2001 (66 FR 29384). 
This vernal pool complex represents the southwestern limit of occupied 
vernal pool fairy shrimp habitat. It is also a unique habitat for 
vernal pool fairy shrimp, therefore, the fairy shrimp in these pools 
may have genetic characteristics important to the overall long-term 
conservation of the species (i.e., they may be genetically different 
from more centrally located populations) (Lesica and Allendorf 1995). 
Conservation of this vernal pool basin and its associated watershed is 
essential to the conservation of the vernal pool fairy shrimp, and the 
Riverside fairy shrimp in southern California, as indicated in the 
Vernal Pools of Southern California Recovery Plan (Service 1998). 
Property ownership and protection within this unit includes CDFG (761 
ha (1,880 ac)), TNC (77 ha (1,902 ac)), and TNC conservation easements 
(150 ha (375 ac)).

Unit 35, Skunk Hollow Unit, Riverside County (97 ha (239 ac))

    The Skunk Hollow vernal pool complex consist of a single, large 
(approximately 14 ha (35 ac)) vernal pool and its essential associated 
watershed in western Riverside County. All the lands within this unit 
are privately owned. Several federally listed species have been 
documented from the Skunk Hollow vernal pool basin. These include the 
threatened vernal pool fairy shrimp (Simovich in Litt 2001), the 
endangered Riverside fairy shrimp

[[Page 59931]]

(Service 2001), the threatened spreading navarretia, and the endangered 
California Orcutt grass (Service 1998). The vernal pool complex and 
watershed is currently protected as part of a reserve established 
within an approved mitigation bank in the Rancho Bella Vista Habitat 
Conservation Plan (HCP) area and as part of the conservation measures 
contained in the Assessment District 161 Subregional HCP. While neither 
HCP include the vernal pool fairy shrimp as a covered species, both 
HCPs provide protection for the vernal pool complex and its associated 
watershed in perpetuity. Further, the HCPs address the endangered 
Riverside fairy shrimp as a covered species. Because we believed that 
the management and protections afforded the vernal pool complex and the 
Riverside fairy shrimp were adequate for the long-term conservation of 
this complex and this species, and it is in the long-term survival 
interest of the species to preserve the partnerships that we had 
developed with the local jurisdiction and project proponents in the 
development of the HCPs, we excluded the Skunk Hollow vernal pool 
complex from critical habitat for the Riverside fairy shrimp. We do not 
believe that this exclusion from critical habitat would result in the 
extinction of this Riverside fairy shrimp.
    Even though the two HCPs do not have the vernal pool fairy shrimp 
listed as a covered species, we believe that the protections and 
management afforded the Skunk Hollow vernal pool complex and the other 
listed vernal pool species through the terms and conditions of those 
HCPs are adequate to ensure the long-term conservation of the vernal 
pool fairy shrimp as well. Therefore similar to the Riverside fairy 
shrimp, we believe that the benefits of the exclusion of the Skunk 
Hollow vernal pool complex from critical habitat for the vernal pool 
fairy shrimp outweighs the benefit of its inclusion. Additionally, we 
do not believe that this exclusion would result in the extinction of 
the vernal pool fairy shrimp.

Vernal Pool Tadpole Shrimp Criteria

    In proposing critical habitat units for vernal pool tadpole shrimp 
we evaluated the life history and current distribution of the species, 
the primary constituent elements, and the threats to the species. This 
information allowed us to determine which areas are likely to 
contribute to the conservation of vernal pool tadpole shrimp and to 
delineate units so that threats to this species might be minimized.
    CNDDB (2001) estimates that 32 percent of the remaining occurrences 
of this species are threatened by development and agricultural 
conversion. Other vernal pool tadpole shrimp occurrences are threatened 
by off road vehicle use, road construction and maintenance, mining, and 
landfill construction (CNDDB 2001). Several occurrences are threatened 
by intentional discing and draining of their habitats (CNDDB 2001). 
Vernal pool tadpole shrimp occurrences have been extirpated as a result 
of urban development, primarily in Sacramento and Tehama counties.
    Numerous occurrences of vernal pool tadpole shrimp are threatened 
by altered hydrology. In some cases vernal pool tadpole shrimp habitat 
has been altered so that it contains water year round, allowing 
predators such as bullfrogs and fish to colonize the areas (CNDDB 
2001). In other cases artificial run off has resulted in the delivery 
of materials that destroy vernal pool water quality, including 
pesticides from vineyards and other irrigated agricultural lands, 
pesticides from golf courses, and sediment from surrounding 
developments (CNDDB 2001). Several vernal pool tadpole shrimp 
occurrences are threatened by wetland management activities that are 
designed to transform their vernal pool habitats into permanent marshes 
for the benefit of other species (CNDDB 2001). Several other 
occurrences are threatened by the construction of drainage ditches, 
which artificially drain vernal pool tadpole shrimp habitats (CNDDB 
2001).

Vernal Pool Tadpole Shrimp Unit Review

    We conducted a regional review across the current range of vernal 
pool tadpole shrimp to evaluate and select areas that are essential to 
the conservation of the species and that may require special management 
actions. Important factors we considered were the presence of vernal 
pool tadpole shrimp and the presence of the primary constituent 
elements essential to the conservation of the species. We identified 
areas that support vernal pool tadpole shrimp occurrences identified by 
CNDDB (2002) within large vernal pool complexes mapped by Holland 
(1998) and other local sources throughout the range of the species. We 
have identified the areas necessary to maintain vernal pool tadpole 
shrimp range and distribution and to include some of the different 
kinds of habitats in which the species is known to occur. A specific 
description of each area is outlined below.

Unit 1, Stillwater Plains Unit, Shasta County (1,849 ha (4,569 ac))

    This unit is proposed as critical habitat for vernal pool tadpole 
shrimp because it contains the species (CNDDB 2002) within vernal pools 
mapped by Holland (1998) which are found on old alluvial terraces above 
the Sacramento River, often on Redding and Corning soil complexes 
(Shasta County 2001). Generally these pools range in size, from small 
(10 m\2\) (30 sq ft.) to several ha (ac) in size at the Stillwater 
Plains area. These vernal pools provide feeding and sheltering habitat 
for the species and remain inundated for sufficient lengths of time to 
allow vernal pool fairy shrimp to hatch, mature, and reproduce.
    This unit represents critical habitat for vernal pool fairy shrimp 
because it contains all of the primary constituent elements for the 
species, and supports systems of hydrologically interconnected pools 
and swales within a matrix of surrounding uplands that together form 
hydrologically and ecologically functional units called vernal pool 
complexes. These features contribute to the filling and drying of the 
vernal pool, and maintain suitable periods of pool inundation, water 
quality, and soil moisture for vernal pool crustaceans to complete 
their life cycles.
    The vernal pool tadpole shrimp within this unit were found to be 
genetically different from other populations, particularly those in the 
foothills of the Sierra Nevada (King 1996). This unit also comprises 
the northern extent of the species range in California, and such 
isolated populations may be essential to the overall long-term 
conservation of the species (Fugate 1992, 1998, Lesica and Allendorf 
1995). The boundaries of the unit were delineated to include the 
interconnected pools, swales, and associated uplands mapped by Holland 
(1998) that contribute to the filling and drying of the vernal pools 
where vernal pool fairy shrimp occur, and which maintain suitable 
periods of pool inundation, water quality, and soil moisture for vernal 
pool tadpole shrimp hatching, growth, reproduction, and dispersal.
    This unit includes the Stillwater Plains Conservation Bank. The 
Stillwater Plains Conservation Bank was established specifically for 
the conservation of vernal pool tadpole shrimp, and has been used as 
mitigation for the destruction of other vernal pool tadpole shrimp 
habitats throughout the northeastern Sacramento Valley area. Most of 
the land included within this unit is privately owned, but 52 ha (130

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ac) of that is protected by WRP easements or agreements. The BLM owns 
17 ha (42 ac). Urban expansion from the Redding Area, and conversion 
from grazing to other agricultural practices continue to threaten 
vernal pool tadpole shrimp occurrences throughout this unit.
    This unit is located in the area east of the Redding Municipal 
Airport between Airport Road to the west and Deschutes Road to the 
east. The unit extends to Dersch Road in the south and towards Lassen 
Park Highway in the north. This unit comprises a portion of the 
Stillwater Plains. This unit overlaps slender Orcutt grass Unit 2B and 
vernal pool fairy shrimp unit 5. Other sensitive species occurring 
within this unit include Red Bluff dwarf rush (Juncus leiospermus var. 
leiospermus), California linderiella (Linderiella occidentalis), 
Henderson's bent grass (Agrostis hendersonii), and four angled spike 
rush (Eleocharis quadrangulata).

Unit 2, Dales Unit, Shasta and Tehama Counties (20,446 ha (50,522 ac))

    This unit is proposed as critical habitat for vernal pool tadpole 
shrimp because it contains the species and vernal pools, swales, and 
other ephemeral wetlands and depressions of appropriate sizes and 
depths necessary for vernal pool tadpole to complete their life cycle 
(Holland 1998, CNDDB 2001). This unit is one of the few areas where 
vernal pool tadpole shrimp are known to occur in Northern Mudflow 
vernal pools. Northern Mudflow vernal pools are generally small and 
tend to be inundated for relatively short periods of time (Keeler-Wolf 
et al. 1998).
    The boundaries of the unit were delineated to include the 
interconnected pools, swales, and associated uplands mapped by Holland 
(1998) that contribute to the filling and drying of the vernal pools 
where vernal pool fairy shrimp occur, and which maintain suitable 
periods of pool inundation, water quality, and soil moisture for vernal 
pool tadpole shrimp hatching, growth, reproduction, and dispersal.
    This unit contains some of the largest remaining vernal pool 
complexes supporting vernal pool tadpole shrimp in the northern portion 
of the species range, including the Dales Plains. These areas provide 
relatively undisturbed, hydrologically intact vernal pool habitats that 
will likely continue to support natural vernal pool ecosystem processes 
and maintain suitable habitat conditions for vernal pool tadpole 
shrimp. This unit also provides habitat for migratory waterfowl that 
aid in the dispersal of vernal pool tadpole shrimp and other vernal 
pool crustacean cysts.
    Land ownership within this unit includes BLM (6,226 (15,383 ac)), 
CDFG (392 ha (981 ac)), State Land Commission (40 ha (100 ac)). The 
CDFG administers approximately 17 ha (42 ac) and the TNC has 
conservation easements on 6,230 (15,575 ac) within this unit. The 
remaining lands included within this unit are privately owned. The CDFG 
has protected some vernal pool areas at Dales Lake Ecological Reserve. 
The importance of these vernal pool habitats has been recognized by a 
number of state, local, and Federal agencies, and they have been the 
focus of several conservation planning efforts. Portions of the CDFG 
Battle Creek Wildlife Area are found within this unit but the amount of 
vernal pool habitat currently protected within the unit is very small. 
Vernal pool habitats within this unit are fragmented and threatened by 
urban expansion, subdivision of ranches and land grants, and conversion 
from grazing to other agricultural practices.
    This unit is located from Battle Creek on the Shasta/Tehama County 
line south of Balls Ferry to Paynes Creek near Dales. The vernal pool 
habitats west of Inskip Hill are included in this unit, as well as the 
area west of the Sacramento River known as Table Mountain and Table 
Mountain Lake. This unit coincides with Unit 3 for slender Orcutt 
grass. Other vernal pool species occurring within this unit include 
Bogg's Lake hedge-hyssop, Red Bluff dwarf rush, legenere, California 
linderiella, Ahart's paronychia, Henderson's bent grass, and Sanford's 
arrowhead.

Unit 3, Vina Plains Unit, Tehama and Butte Counties (23,883 ha (59,015 
ac))

    This unit is proposed as critical habitat because it contains 
occurrences of vernal pool tadpole shrimp (CNDDB 2001) living within 
large vernal pool grassland areas that support aggregations or systems 
of hydrologically interconnected pools, swales, and other ephemeral 
wetlands and within a matrix of surrounding uplands that together form 
hydrologically and ecologically functional units (EPA 1994, Holland 
1998, Tehama County 1999). These features contribute to the filling and 
drying of the vernal pool, and maintain suitable periods of pool 
inundation, water quality, and soil moisture for vernal pool tadpole 
shrimp hatching, growth and reproduction, and dispersal. This unit is 
one of the few areas where vernal pool tadpole shrimp are known to 
occur in Northern Basalt Flow vernal pools. Northern Basalt Flow vernal 
pools are limited to ancient terraces and hilltops that comprise some 
of the oldest geologic formations in California. This unit also 
provides habitat for migratory waterfowl that aid in the dispersal of 
vernal pool tadpole shrimp and other vernal pool crustacean cysts.
    This unit contains the vernal pool grassland area known as Vina 
Plains, which is managed by TNC. The Vina Plains area has been the 
focus of a number of research projects, including long-term adaptive 
management and monitoring efforts evaluating the effects of grazing and 
fire on vernal pool plants, animals, and ecosystems (Griggs 2000). Much 
of the basic life history information known about vernal pool 
crustaceans was collected at Vina Plains (e.g., Lanway 1974, Ahl 1991, 
Syrdahl 1993, Gallagher 1996).
    The majority of the lands included within this unit are privately 
owned. This unit contains TNC's Vina Plains preserve as well as other 
TNC lands 2,264 ha (5,660 ac) and conservation easements 4,348 ha 
(10,870 ac). The unit also includes 57 ha (142 ac) of private lands 
protected by WRP easements or agreements. This unit is located in the 
northeastern portion of the Sacramento Valley from Deer Creek in Tehama 
County to Big Chico Creek north of Chico in Butte County. This unit is 
one of only two vernal pool tadpole shrimp units within the 
Northeastern Sacramento Valley vernal pool region identified by CDFG 
(Keeler Wolf et al. 1998). The unit extends south and east of the 
Sacramento River paralleling the low elevation foothill region of the 
Sierra Nevada. This unit coincides with Unit 7 for vernal pool fairy 
shrimp, and incorporates Unit 1 for Conservancy fairy shrimp, Units 4 
for slender Orcutt grass, Unit 2 for Greene's tuctoria, Unit 1 for 
hairy Orcutt grass, Unit 1 for Hoover's spurge, and Units 1 and 2 for 
Butte County meadowfoam. Other vernal pool species occurring within 
this unit include Bogg's Lake hedge-hyssop, Red Bluff dwarf rush, 
Douglas' pogogyne, western spadefoot toad, legenere, California 
linderiella, California tiger salamander, Ahart's paronychia, 
Henderson's bent grass, Sanford's arrowhead , and dwarf downingia.

Unit 4, Oroville Unit, Butte and Yuba Counties (15,975 ha (39,474 ac))

    This unit is proposed as critical habitat for vernal pool tadpole 
shrimp because it contains occurrences of the species and vernal pools, 
swales, and other ephemeral wetlands and depressions of appropriate 
sizes and depths necessary for vernal pool tadpole shrimp to complete 
their life cycle (Holland 1998, CNDDB 2001, Silveira


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