[Federal Register: October 7, 2010 (Volume 75, Number 194)]
[Proposed Rules]
[Page 62070-62095]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr07oc10-27]
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DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[Docket No. FWS-R8-ES-2010-0013]
[MO 92210-0-0008-B2]
Endangered and Threatened Wildlife and Plants; 12-month Finding
on a Petition to list the Sacramento Splittail as Endangered or
Threatened
AGENCY: Fish and Wildlife Service, Interior.
ACTION: Notice of 12-month petition finding.
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SUMMARY: We, the U.S. Fish and Wildlife Service, announce a 12-month
finding on a petition to list the Sacramento splittail (Pogonichthys
macrolepidotus) as endangered or threatened under the Endangered
Species Act of 1973, as amended. After review of all available
scientific and commercial information, we find that listing the
Sacramento splittail is not warranted at this time. However, we ask the
public to submit to us any new information that becomes available
concerning the threats to the Sacramento splittail or its habitat at
any time.
DATES: The finding announced in this document was made on October 7,
2010.
ADDRESSES: This finding is available on the Internet at http://
www.regulations.gov at Docket Number FWS-R8-ES-2010-0013. Supporting
documentation we used in preparing this finding is available for public
inspection, by appointment, during normal business hours at the U.S.
Fish and Wildlife Service, San Francisco Bay Delta Fish and Wildlife
Office, 650 Capitol Mall, Sacramento, CA 95814. Please submit any new
information, materials, comments, or questions concerning this finding
to the above street address.
FOR FURTHER INFORMATION CONTACT: Dan Castelberry, San Francisco Bay
Delta Fish and Wildlife Office (see ADDRESSES); by telephone at 916-
930-5632; or by facsimile at 916-930-5654. If you use a
telecommunications device for the deaf (TDD), please call the Federal
Information Relay Service (FIRS) at 800-877-8339.
SUPPLEMENTARY INFORMATION:
Background
Section 4(b)(3)(B) of the Endangered Species Act of 1973, as
amended (Act) (16 U.S.C. 1531 et seq.), requires that, for any petition
to revise the Federal Lists of Endangered and Threatened
[[Page 62071]]
Wildlife and Plants that contains substantial scientific or commercial
information that listing the species may be warranted, we make a
finding within 12 months of the date of receipt of the petition. In
this finding, we will determine that the petitioned action is: (1) Not
warranted, (2) warranted, or (3) warranted, but the immediate proposal
of a regulation implementing the petitioned action is precluded by
other pending proposals to determine whether species are tendangered or
threatened, and expeditious progress is being made to add or remove
qualified species from the Federal Lists of Endangered and Threatened
Wildlife and Plants. Section 4(b)(3)(C) of the Act requires that we
treat a petition for which the requested action is found to be
warranted but precluded as though resubmitted on the date of such
finding, that is, requiring a subsequent finding to be made within 12
months. We must publish these 12-month findings in the Federal
Register.
Previous Federal Actions
Please refer to the final listing rule (64 FR 5963) for a
discussion of Federal actions that occurred prior to February 8, 1999.
Please refer to the Notice of Remanded Determination of Status for the
Sacramento Splittail (68 FR 55139) for a discussion of Federal actions
that occurred after February 8, 1999, and prior to September 22, 2003.
It is our intent, in this document, to reiterate and discuss only those
topics directly relevant to this decision.
On September 22, 2003, the Service published a Notice of Remanded
Determination of Status for the Sacramento Splittail in the Federal
Register (68 FR 55139) that removed the Sacramento splittail from the
List of Endangered and Threatened Wildlife (50 CFR 17.11(h)). On August
13, 2009, the Center for Biological Diversity (CBD) filed a complaint
in U.S. District Court for the Northern District of California,
challenging the Service on the merits of the 2003 determination
alleging improper political influence. In a settlement dated February
1, 2010 (Case4:09-cv-03711-PJH), the Service agreed to open a 30-day
public comment period for a new 12 month finding to allow for the
submission of additional information by the public. The Service also
agreed to submit to the Federal Register a new status review and 12-
month finding as to whether listing the Sacramento splittail is
warranted or not warranted. If warranted, the Service further agreed to
publish, concurrently with the 12-month finding, a proposed rule to
list the Sacramento splittail before September 30, 2010 and a final
determination on or before September 29, 2011.
Definitions
To assist the reader in understanding terminology used in this
determination, we have provided below several terms with their
corresponding definitions as they are used in this document. As used in
this determination, the term ``Delta'`` refers to all tidal waters
contained within the legal definition of the San Francisco Bay-
Sacramento-San Joaquin River Delta, as delineated by section 12220 of
the State of California's Water Code. Generally, the Delta is contained
within a triangular area that extends south from the City of Sacramento
to the confluence of the Stanislaus and San Joaquin Rivers at the
southeast corner and Chipps Island in Suisun Bay at the southwest
corner. The term ``Estuary'' as used in this determination, refers to
the collective tidal waters contained in the Sacramento and San Joaquin
Rivers, the Delta, and San Pablo and San Francisco bays.
Species Information
Species Description
The Sacramento splittail is a fish species native to central
California and represents the only extant species in its genus in the
world (Baerwald et al. 2007, p. 160). Splittail can grow to a length of
40centimeters (cm) (15 inches (in.)), and have an elongate body, small
head, and enlarged upper tail lobe. Their body coloration is dusky
olive gray on the back and silver on the sides. During breeding season,
their fins become tinged with red-orange. Additionally, males develop
white tubercles on their heads and become darker in color during the
breeding season (Moyle 2002, p. 146).
Taxonomy
Splittail were first described in 1854 by W.O. Ayres as Leuciscus
macrolepidotus and by S.F. Baird and C. Girard as Pogonichthys
inaeqilobus. Although Ayres' species description is accepted, the
species was assigned to the genus Pogonichthys in recognition of the
distinctive characteristics exhibited by the two splittail species P.
ciscoides and P. macrolepidotus (Hopkirk 1973, p. 24). Pogonichthys
ciscoides, endemic to Clear Lake, Lake County, California, has been
extinct since the early 1970s. The Sacramento splittail is currently
classified as Pogonichthys macrolepidotus. Recent studies have revealed
two populations of splittail that differ in their genetic makeup, one
in the Napa/Petaluma drainages (hereafter referred to as the San Pablo
population) and one in the greater Central Valley drainage (hereafter
referred to as the Delta population) (Baerwald et al.2007, pp. 159-
167).
Distribution
Historically, Sacramento splittail were found as far north as
Redding on the Sacramento River. Splittail were also found in the
tributaries of the Sacramento River as far as the current Oroville Dam
site on the Feather River and Folsom Dam site on the American River
(Rutter et al. 1908, p. 131). Along the San Joaquin River, splittail
were harvested by native peoples in Tulare and Buena Vista Lakes where
splittail bones have been found in archeological middens (Moyle et al.,
2004, p. 7). In the San Francisco Bay area, splittail have historically
been reported at the mouth of Coyote Creek in Santa Clara County and
the Southern San Francisco Bay (Snyder et al. 1905, pp. 327-338).
Splittail were documented in Suisun and Napa marshes as well as Suisun
Bay in the 1950's (Caywood . 1974, p. 29-65).
Splittail occur in the San Francisco estuary and its tributaries
and are found most often in slow moving sections of rivers and sloughs
including dead end sloughs and shallow edge habitats (Moyle 2002, p.
147; Daniels and Moyle 1983, p. 653; Feyrer et al. 2005, pp. 164-165).
Recent studies have shown the splittail's range in the Sacramento, San
Joaquin, Napa, Mokelumne and Petaluma rivers is significantly greater
than previously thought when it was first petitioned in the early
1990's as a threatened species (Sommer et al. 2007, pp. 27-28; Sommer
et al. 1997, p. 970). The following chart created by Sommer and
featured in his splittail paper follows (Sommer et al. 2007, p. 28).
[[Page 62072]]
Table 1. Upstream-most locations of historical and recent splittail collections (1998-2002). River kilometer (rkm) is the distance from the mouth of the
river. Location (rkm) of splittail collection
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Recent (Freyer et al.
River System Historic (Rutter 1908) 1970s (Cawood 1974) Mid- 1990s (Sommer et 05) unless noted Distance to first
al. 1997) otherwise dam\a\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Sacramento 483 387 331 391\b\ 387
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Feather 109 Present 94 94\c\ 109
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American 49 37 19 No new data 37
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San Joaquin Widespread Present 201 218.5\d\ 295
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Mokelumne NA 25 63 96\e\ 63
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Napa NA 21 10 32 NA
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Petaluma NA 25 8 28 NA
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\a\ Lowest dams in reach of river are Red Bluff (Sacramento), Oroville (Feather), Nimbus (American), Sack (San Joaquin), and Woodbridge (Mokelumne).
Woodbridge is a seasonal dam. Napa River is not dammed within the range of splittail; first dam was removed from the Petaluma River in 1994.
\b\ D. Killam, California Department of Fish and Game, personal communication.
\c\ B. Oppenheim, NOAA Fisheries, personal communication.
\d\ R. Baxter, California Department of Fish and Game, unpublished data.
\e\ J. Merz, East Bay Municipal Utility District, November 2000.
Distribution on the Sacramento River over the past 30 years has
consistently ranged at least 232 to296 river kilometers (rkm) (144
to184 miles (mi)) upstream of the estuary (Feyrer et. al. 2005, pp.
163-167). The consistent finding of splittail more than 200 rkm (124
mi) upstream of the Estuary may represent a population persisting there
or may reflect the long distance that splittail migrate during dry
years (Feyrer et al. 2005, pp. 165-166). Juvenile splittail have been
recorded at the Glenn-Colusa Irrigation District Intake at rkm 331 (206
mi) on the Sacramento River year-round from 1994 - 2001. It is unknown
why these individuals do not migrate downstream after spawning as do
the majority of splittail (Feyrer et al. 2005, pp 165-166). Splittail
have been documented on the Toulumne River to rkm 27.4 (mi 17) (Heyne
2003, pers. comm.) and on the Merced River to rkm 20.9 (13 mi) ( Heyne
2003, pers. comm.). Splittail have been recorded in recent times from
within Salt Slough (Baxter 1999a, p. 10; 1999b, p. 30). A 1998
California Department of Fish and Game (CDFG) gillnet survey of the
tidal reaches of the Lower Walnut Creek found splittail to be the most
abundant fish in the creek (Leidy et al. 2007). Splittail are found in
the Napa Marsh during years with high freshwater flow, but are rare
during years of low freshwater outflow (Baxter 1999a, p. 11).
Splittail can utilize a variety of habitats and having no known
collection in an area does not mean that splittail are not there
because it is impractical to survey the entire Delta. Splittail have
been observed in a number of tributaries of major rivers such as the
Sacramento and San Joaquin and are likely distributed much more widely
in small creeks and marshes throughout the lower portions of the
Estuary than known collections indicate (Kratville 2010, pers comm.).
Suisun Marsh and Bay contain the largest areal extent of shallow water
habitat available to the splittail and likely have the greatest
concentrations of the species.
Splittail's spawning habitat includes the natural and newly-
restored floodplains of the Cosumnes River, managed floodplains such as
the Yolo and Sutter bypasses, and disjunct segments of floodplain
adjacent to the Sacramento and San Joaquin rivers and tributaries.
These areas approximate the large, open, shallow-water areas which once
existed throughout the Delta (Sommer et al. 1997, p. 971). The largest
portion of splittail spawning habitat occurs in the Yolo Bypass and
higher splittail young-of-the-year abundances are strongly correlated
with the flooding of the Yolo Bypass. The best spawning conditions for
splittail occur in the bypass when water remains in the bypass until
fish have completed spawning (at least 30 days), and larvae are able to
swim out on their own during the draining process.
In years where the Yolo and Sutter bypasses are not inundated for
at least 30 days, splittail spawning is confined primarily to the
natural and newly restored floodplains of the Cosumnes River and the
margins of rivers and other floodplain features that are inundated at
lower river stages. The Cosumnes River is unique in that it is the only
major river flowing into the Delta that does not host a major dam.
There are indications, based on presence of larvae and juveniles, that
spawning in the Sacramento River occurs relatively far upstream at
Colusa (Baxter 1999a, p. 8; 1999b, p. 29). Splittail also utilize the
San Joaquin River for spawning in wet years when river flow exceeds the
capacity for storage and flooding occurs. The Tuolumne, Cosumnes,
Feather, American, Napa, and Petaluma Rivers, and numerous other
smaller waters also support splittail spawning activity.
In summary, the geographic distribution of the splittail has not
decreased detectably over the last several decades and is in fact
larger than estimated in our last listing decision (Sommer et al. 2007,
pp.27-28; 68 FR 55139).
Habitat Requirements
Although primarily a freshwater species, splittail tolerate
salinities as high as 10 to 18 parts per thousand (ppt) (Moyle and
Yoshiyama 1992). Salinity tolerance in splittail increases in
proportion to body length; adults can tolerate salinities as high as 29
ppt for short periods in laboratory conditions, but experience loss of
equilibrium (bodily balance) when salinities exceed 23 ppt (Young and
Cech 1996, p. 668). Hospitable temperatures for non-breeding splittail
range from 5 to 24[deg] Celsius (C) (75[deg] Fahrenheit (F)) although
acclimated fish can survive temperatures up to 33[deg]C (91[deg] F) for
short periods of time (Young and Cech 1996, pp. 667-675). Splittail are
also tolerant
[[Page 62073]]
of low dissolved oxygen and can be found in water where levels are
around 1 mg O\2\ L -\1\ (Moyle et al. 2004, p. 13).
Splittail are frequently found in areas subject to flooding because
they require flooded vegetation for spawning and rearing. Historically,
the major flood basins (e.g., Colusa, Sutter, American, and Yolo
basins; Tulare, Buena Vista, and Kern lakes) distributed throughout the
Sacramento and San Joaquin valleys provided spawning and rearing
habitat. These flood basins have all been reclaimed or modified for
flood control purposes (i.e. as bypasses), and much of the floodplain
area adjacent to the rivers is now inaccessible behind levees.
Splittail make use of the Sutter Bypass, and particularly heavy use
of the Yolo Bypass, for spawning under certain hydrologic conditions.
The shallow, vegetated waters of the bypasses provide excellent rearing
conditions for juvenile fish (Sommer et al. 2001, p. 11). The bypasses
are primarily flood control facilities and secondarily, passively
operated as agricultural lands. These lands are also managed for
waterfowl and other wildlife habitat. Splittail using the bypasses are
subject to the same threats found elsewhere, such as habitat loss,
environmental contamination, harmful reservoir operations, competition
with and predation by non-native fish, and so forth.
The bypasses are only fully flooded when flows in the Sacramento
River reach a certain level. The Yolo Bypass becomes inundated when the
Sacramento River flow rate at the Freemont Weir exceeds 1,600 cubic
meters per second (cms) (56,503 cubic feet per second (cfs)). This
occurs when the River reaches approximately 9.0 meters (m) (30 feet
(ft.) (National Geodetic Vertical Datum standard) in depth at the
Freemont Weir (Sommer et al. 2001, pp. 7-8). Partial flooding of the
Yolo Bypass via high flows from Cache and Putah creeks can occur
independently regardless of Sacramento River flows. Due to the
unpredictable flooding frequencies and duration of the bypass,
splittail, having migrated long distances upstream, could arrive at
floodplains that have not been inundated and therefore the splittail
could be denied the opportunity to spawn. In those cases where adult
splittail successfully spawn, the eggs or larvae could become trapped
and killed if waters recede too rapidly. Insufficient duration of
floodplain inundation could also force egress of juvenile splittail
before they have attained a size and swimming ability sufficient to
avoid predation. The annual splittail spawning and reproductive success
is strongly correlated with frequency and duration of Yolo bypass
inundation (Sommer et al. 2007, pp. 33-34).
The Fremont Weir has been overtopped--resulting in Yolo Bypass
inundation--19 of the last 31 years with 10 of these years producing
inundation durations of more than 30 days (DWR 2010a, pp. 1-2).
Inundation durations of 30-90 days are needed to produce robust
splittail year classes on the bypass (Kratville 2010, pers. comm.).
According to the ST5 (T. C. Foin) model, the inundation of floodplains
that splittail utilize as spawning habitat must occur at a minimum of
every 7 years for a minimum of 30 days for splittail populations to
persist. Bypasses and other floodplains have historically been
exceeding these parameters and we have no evidence that suggests they
will not continue to do so in the foreseeable future.
The Yolo Bypass supports agricultural crops such as corn and
safflower and can support tomatoes in non-flood years. Optimal flooding
conditions for the splittail (February through May) have negative
effects on agricultural production in the area destroying and damaging
crops, eroding soils and decreasing overall yields (Yolo Bypass
Management Strategy 2001, ch. 2 p. 6). Because Yolo Bypass inundation
is likely to be one of the most important factors in determining the
continued production of high splittail population numbers, cooperation
on the flood management between the landowners of the bypass and
resource management agencies is essential.
Splittail spawning occurs over flooded vegetation in freshwater
marshes, sloughs, and shallow reaches of large rivers with depths of at
least 1m (3.3 ft) (Moyle et al. 2007 , pp. 1-27). Observations of
splittail spawning have indicated the species spawns at depths of less
than 1.5 m (4.9 ft) in the Cosumnes River floodplain and at depths of
less than 2 m (6.6 ft) in Sutter Bypass (Moyle et al. 2004, pp. 16-17).
These studies show that splittail spawn in water depths between 1 to 2
m (3.3 to 6.6 ft) depending on location of spawning. Splittail may not
spawn again in the year following a successful effort (Moyle et. al.
2004, p. 32).
It is speculated that Suisun Marsh is the late-stage rearing area
for juvenile splittail hatched and reared in the extensive spawning
habitat found within the Yolo Bypass because water flowing out of the
Yolo Bypass tends to stay on the north side of the delta and be drawn
into Suisun Marsh (Moyle et al. 2004, p. 31).
Biology
Splittail are relatively long-lived and larger fish may be 8 to 10
years old (Moyle 2002). Splittail reach about 110 millimeters (mm) (4.3
in) standard length (SL) (tip of the snout to the posterior end of the
last vertebra)in their first year, 170 mm (6.6 in) SL in their second
year, and 215 mm (8.4 in) SL in their third year (Moyle 2002, p. 148).
Male and female splittail generally mature by the end of their second
year, but some males mature in their first year and some females do not
mature until their third year (Daniels and Moyle 1983, p.650).
Estimates of splittail fecundity have shown high variability in
numbers of eggs produced. Caywood (1974, p. 4015) found a mean of 165
eggs per mm of SL of fish sampled and reported a maximum of 100,800
eggs in one female. Feyrer and Baxter (1998, p. 123) found a mean of
261 eggs per mm of SL and a fecundity range of 28,416 to 168,196 eggs.
Bailey et al. (1999) examined fish held for a considerable time in
captivity and found that fecundity ranged from 24,753 to 72,314 eggs
per female, which most closely agrees with Caywood's (1974, p. 4015)
observations.
Splittail are benthic (feeding in the bottom of the water column)
foragers that mainly feed in the daytime. Composition of splittail gut
contents has revealed that they feed almost exclusively on aquatic
invertebrates with chironomid larvae making up the largest portion of
the diet in all areas except the Petaluma River where copepods make up
the largest portion of the diet (Feyrer et al. 2007a, p. 1398). Until
the 1980's, opossum or mysid shrimp (Neomysis mercedis), made up a
large portion of the diet along with amphipods and harpacticoid
copepods (Moyle et al. 2004, p. 14). Introductions of the Asiatic clam
(Corbicula fluminea) in 1945 and more importantly the overbite clam
(Corbula amurensis) first recorded from the estuary in 1986) were
followed by a sharp decline in shrimp abundance that started in 1987
and continued through 1999 (Feyrer et al. 2003, p. 283). Splittail have
shifted their diet from prey items such as mysid shrimp to a diet
increasingly focused on bi-valves, in particular the overbite clam.
Opossum shrimp in splittail gut contents were reduced from 24 percent
(historically) to 2 percent by 2003 (Feyrer et al. 2003, pp. 277-288;
Kratville 2010, pers comm.). In the Estuary, clams, crustaceans, insect
larvae, and other invertebrates also are found in the adult diet.
Larvae feed mainly on plankton composed of small
[[Page 62074]]
animals (zooplankton), moving to small crustaceans and insect larvae as
body size increases (Kurth and Nobriga 2001, EIP newsletter vol. 14,
num.3, p. 41).
Splittail populations fluctuate annually, depending on spawning
success, which is positively well-correlated with freshwater outflow
and the availability of shallow water habitat with submerged vegetation
(Daniels and Moyle 1983; Sommer et al. 1997). Sexual maturity is
typically reached by the end of their second year. Splittail are a
migratory species that travel upstream into freshwater floodplain
habitat to spawn. The onset of spawning is associated with rising water
levels, increasing water temperatures, and increasing day length. Peak
spawning occurs from February through May, although records of spawning
exist for late January to early July (Wang 1986). One temporally stable
cue for splittail is the timing of the vernal equinox (Feyrer 2006, p.
221). Peak flow from the Central Valley enters the Estuary
approximately at the same time as the vernal equinox (Feyrer 2006, p.
221) and these coinciding events commence splittail migration. In some
years, most spawning may take place within a limited period of time.
For instance, in 1995, a year of high spawning activity, most splittail
spawned over a short period in April (Moyle et al. 2004, p. 16). Within
each spawning season, older fish reproduce first, followed by younger
individuals (Caywood 1974, p. 50).
Bailey (1994, p. 3) has documented that splittail eggs hatch in 3
to 5 days at 18.5[deg] C, (65.3[deg] F). Bailey (1994, p. 3) also found
that at 5 to 7 days after hatching, the yolk sac is absorbed and the
diet begins to include small rotifers. Splittail larvae remain in
shallow, weedy areas close to spawning sites for 10 to 14 days and move
into deeper water as they mature and swimming ability increases (Sommer
et al. 1997, pp. 961-976). When the flood waters recede juveniles
typically leave the flooded areas and move downstream in May, June, and
July to rear in estuarine marshes (Moyle et al. 2004, p. 17). Splittail
can be easily identified at 20 to 25 mm (0.8 to 1.0 in) total length
(TL) and become fairly active swimmers at this time (Moyle et al. 2004,
p. 17).
Abundance
History of abundance models and evaluations
An estimate of splittail abundance has never been performed;
however, survey data have been used to construct indices of abundance
that have been used in the past to assess population trends (Sommer et
al. 2007, p 29; Moyle et al. 2004, p 7). In general, the applicability
of survey data to a particular use arises from two factors: (1) How the
data are collected; and (2) how the data are used to estimate or to
index abundance. The key point with regard to the first factor is the
degree to which the sample collected is representative of the sampled
population. Gear type, configuration, and method of deployment all
contribute to species, sizes, and life stages collected. Unequal
vulnerability of different sizes of fish to a given sampling protocol
results in systematic error in population estimation. Fish behavior,
both between species and between life stages, also contributes to
sampling error, as does habitat variation, because gear performance
often differs among habitat types. The efficiency of open-water, or
pelagic, sampling may be affected by physical factors such as flow
velocity and turbidity, both in terms of gear performance and fish
behavior.
Splittail are a benthic (near-bottom-dwelling) species, often occur
in shallow edge habitat, and feed most actively in early morning (Moyle
et al. 2004, p 8; Moyle 2002, p 148). Splittail would not be expected
to be collected efficiently in surveys that do not sample channel edges
and bottom habitats effectively. Further, while combining data from the
various surveys provides reasonably good coverage of the geographic
range of splittail, individual surveys are often fairly limited in
geographic scope. All surveys suffer from selection biases due to the
type of gear deployed and the method of deployment (Ricker et al. 1975,
pp 70-73; 92). None of the surveys used to construct the indices used
to monitor the relative abundance of splittail was designed
specifically to sample splittail, and each is limited in some manner in
its ability to adequately represent splittail population trends.
Therefore, the data collected do not represent a quantitative estimate
of population size.
The surveys and their limitations are described in the Service's
Notice of Remanded Determination of Status for the Sacramento Splittail
(68 FR 55139). Sommer et al. (2007, pp 29-30) and Moyle et al. (2004,
pp 8-13) also explain some of the important limitations of the surveys
with respect to splittail. A chart summarizing the surveys and their
limitations is provided below.
Table 2. Summary of splittail sampling surveys
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Survey Brief Description Years Pros Cons
----------------------------------------------------------------------------------------------------------------
CDFG Fall Mid--Water Trawl Designed to sample 1967--present Catches all --Targets striped
juvenile striped splittail size bass
bass. classes --Low adult catch
100 sampling sites: rate
San Pablo Bay in --Sampling does
the west to Rio not cover entire
Vista on the lower range
Sacramento River. --Does not sample
and to Stockton on. benthos or
the San Joaquin shallow channel
River. edges
--Some years yield
no splittail
--Splittail are
better able to
see nets in
recent years due
to decreased
turbidity
----------------------------------------------------------------------------------------------------------------
San Francisco Bay Mid--Water Samples west of the 1980--present --Two types of --Does not cover
Trawl and Otter Trawl Survey Delta sampling entire range
seaward to south equipment and --Non--specific;
San Francisco Bay. frequent sampling. targets entire
--Capture all size pelagic or
classes. benthic community
--Incomplete data
between 1989--
1999
--Splittail only
caught in 5
percent or less
of samples
----------------------------------------------------------------------------------------------------------------
[[Page 62075]]
University of California at Long--term study of 1979--present Samples all size --Non--specific;
Davis (UC Davis) Suisun Marsh the classes targets entire
Otter Trawl ecology of the fish community
entire fish --Geographically
community of the limited
marsh at 21 sites --Larger fish less
and 9 sloughs. vulnerable to
trawls
----------------------------------------------------------------------------------------------------------------
Chipps Island Survey U.S. Fish and 1976--present --Samples well --Designed to
Wildlife Service during high flow sample juvenile
conducts a years salmonids
sampling program --Good adult catch --Geographically
for juvenile rates. limited
salmon in the deep --Samples near--
water channel near surface waters
Chipps only
Island, midwater --High turbidity
trawl is pulled at in sampling area
the.
surface in 10 20--
minute hauls per
day during May and
June.
----------------------------------------------------------------------------------------------------------------
FWS Beach Seine Survey Samples 23 stations 1979--present --Broadest --Inconsistent
around Delta with geographical from 1983--1992
15--m beach seine coverage of all --Focused on out--
in low velocity surveys migrating
areas near --Good adult juvenile salmon
shoreline catches. ----Low adult
catch
----------------------------------------------------------------------------------------------------------------
Salvage Operations The Central Valley 1979--present Highest number of --Geographically
Project (CVP) and splittail caught localized--mainly
State Water out of any survey reflective of San
Project (SWP) for both adult Joaquin River
operate fish and juvenile production
screening catches --Catches are
facilities to result of
divert fish away entrainment and
from the pump often cause
intakes into mortality
holding
facilities where
fish are counted,.
measured, and
released..
----------------------------------------------------------------------------------------------------------------
Please refer to February 8, 1999, final listing rule (64 FR 5963)
for a full discussion of methods used to estimate abundance in that
rule. Please refer to the September 22, 2003, Notice of Remanded
Determination of Status for the Sacramento Splittail (68 FR 55139) for
a full discussion of methods used to estimate abundance for that
document. In our January 6, 1994, proposed rule to list the Sacramento
splittail as threatened (59 FR 862), we initially evaluated and
analyzed splittail survey data using a method published by Meng and
Moyle (1995, p. 541) in the Transactions of the American Fisheries
Society. Meng and Moyle used a common data set from the years 1980-1992
to compare point estimates with the Mann-Whitney U-test. We used this
same method during the development of our 1999 final listing rule (64
FR 5963, February 8, 1999), using abundance data provided and updated
by CDFG, California Department of Water Resources (CDWR), and UC Davis.
Using the aforementioned method, the 1999 finding concluded that the
splittail had declined by 62 percent in abundance over the last 15
years.
In a document we published in the Federal Register on August 17,
2001 (66 FR 43145), we requested public comments to assist us in
reanalyzing our splittail abundance data. In that document, we
presented a stratified Mann-Whitney U-test, which represented an
improvement on what essentially remained a Meng and Moyle (1995, pp.
538-549) statistical approach. Following careful consideration of
comments we received from numerous respondents to this document,
including those provided through the peer review process, we concluded
that the abundance indices and Multiple Linear Regression (MLR) model
jointly developed and submitted by CDFG and U.S. Bureau of Reclamation
(USBR) in 2001 (hereafter referred to as the CDFG/USBR MLR Model)
provided the best scientific data (method) available for statistically
evaluating temporal trends of splittail abundance information. We used
this CDFG/USBR MLR Model as the basis of our September 22, 2003, Notice
of Remanded Determination of Status for the Sacramento Splittail (68 FR
55139), instead of the original Meng and Moyle (1995, pp. 540-542)
methodology. We input 20 discrete sets of age-specific abundance
monitoring data into the model. These data sets were obtained from the
surveys described in Table 2 above. Running the model in a ``worst case
scenario'' (alpha < 0.2 significance), we found nine significant
downward-trending data sets and two significant upward-trending data
sets, and we concluded that the population was in decline.
Current evaluation of models and abundance
In light of uncertainties in data for estimating splittail
population abundance, alternative approaches for understanding
population behavior and regulation have been developed. One such
approach is the life history simulation model developed by T. C. Foin
wherein splittail population characteristics can be explored and
compared with known field biology to infer important life stage
survival probabilities and potential conservation strategies (Moyle et
al., 2004, pp. 32-37). Life history simulation models can be
parameterized to the extent possible using relevant field/survey
information, and then used in a series of ``what if'' exercises to
explore simulated population dynamics under selected conditions. Using
the model in this way for sensitivity analysis allows the experimenter
to discern which life stage or life stage characteristic is crucial to
long-term simulated survival, for example, or how often ``sub-optimal''
conditions must occur for the simulated population to be at risk for
extinction. Such population viability analyses (PVAs) can form part of
the basis for the Act's listing decisions where sufficient life stage
parameter estimates are well-known (Shaffer 1981, pp. 131-133; Meffe
and Carroll 1994, pp. 181-182). In the Estuary such a model was used to
confirm field observations that flood plain dynamics and subsequent
spawning response by splittail populations were critical to long-term
population persistence in the absence of other exogenous drivers of
splittail mortality (Moyle et al. 2004, pp. 32-27).
In the present case of the Sacramento splittail, survey data appear
sufficient to
[[Page 62076]]
point to supra-annual patterns of abundance (abundance changes over
several or many years), but do not appear to support parsing into sub-
annual or life-stage specific characterization of splittail population
biology. Inaccuracies associated with intra-annual sampling and both
relative and absolute gear inefficiencies make it very difficult to
discern splittail population dynamics on a sub-annual basis. Life
history traits of the splittail including their dependence on
floodplain hydrology and seasonal flooding of riparian and floodplain
lands make this species quite suited to exploration using population
simulation approaches (Moyle et al., 2004,pp. 13-18, 32).
The T. C. Foin splittail population simulation model (ST5) and
related models have led to the following conclusions regarding
Sacramento splittail population variability and longer-term population
forecasts (Moyle et al., 2004, pp. 32-37). Splittail populations are
highly variable and driven in large measure by rainfall and flooding;
high variability in splittail populations can be modeled focusing on
reproductive effort in those years with substantial added floodplain
inundation. Simulations indicate that several dry years in succession
are not likely to imperil splittail populations. Despite downward
trends in simulated populations of splittail, this model indicates that
low numbers of splittail reproducing along river margins can sustain
the population through long drought periods and that a long series of
dry years is unlikely to drive the splittail to extinction (Moyle et
al. 2004, pp. 36-37). However, a large-scale, regional catastrophe
combined with low population might lead to stochastic extinction. Adult
mortality considered in isolation does not appear to be driving the
population dynamics of splittail in the Estuary or in the models.
Periodic (i.e., a minimum of every 7 years) floodplain inundation seems
essential to long-term population persistence. High variability is a
fundamental property of splittail populations; therefore, little can be
discerned regarding population status within a given survey year from
annual indices of abundance.
The splittail population model ST5 and additional splittail models
built in support of CALFED Science Program objectives use as a
foundation biological characterization supplied by field biologists and
species specialists (Moyle et al. 2004, pp.32-37). Noted in splittail
life history is adaptation to ``estuarine waters with fluctuating
conditions'' (Moyle 2002, p. 147). This includes the ability to respond
to abrupt water level changes and the ability to utilize seasonally
inundated floodplains for spawning. Sacramento splittail are highly
fecund, with some large females reportedly able to produce over 100,000
eggs (Moyle 2002, p. 148). As an iteroparous (producing offspring in
successive cycles), moderately long-lived (5 to 8 years) species with
high reproductive potential, it is not surprising that splittail life
history characteristics allow the species to persist even in the face
of only moderately predictable conditions year-to-year. As long as
favorable spawning conditions occur at a minimum of every 7 years,
populations can remain at relatively low levels and rebound when
favorable spawning conditions occur (Moyle 2002, pp. 34-38). Recent
survey records provided via Interagency Ecological Program (IEP) survey
efforts for the Sacramento splittail have shown this pattern (Meng and
Moyle 1995, pp. 548; Sommer et al., 1997;DWR 2010c, p. 16). This was
demonstrated in 1995 when populations retained a high reproductive
capacity after a substantial decline following several years of drought
(Sommer et al. 1997, p. 971)., Due to the deficiencies in the survey
data discussed above, we are unable to discern a trend in adult
abundance. The young-of-year splittail population experiences a natural
fluctuation in numbers due to drought cycles in the region.
Evaluation of Information Pertaining to the Five Threat Factors
Section 4 of the Act (16 U.S.C. 1533) and implementing regulations
(50 CFR part 424) set forth procedures for adding species to, removing
species from, or reclassifying species on the Federal Lists of
Endangered and Threatened Wildlife and Plants. Under section 4(a)(1) of
the Act, a species may be determined to be endangered or threatened
based on any of the following five factors:
(A) The present or threatened destruction, modification, or
curtailment of its habitat or range;
(B) Overutilization for commercial, recreational, scientific, or
educational purposes;
(C) Disease or predation;
(D) The inadequacy of existing regulatory mechanisms; or
(E) Other natural or manmade factors affecting its continued
existence.
In making this 12-month finding, information pertaining to the
Sacramento splittail in relation to the five factors provided in
section 4(a)(1) of the Act is discussed below. In making our 12-month
finding on the petition we considered and evaluated the best available
scientific and commercial information.
In considering what factors might constitute threats to a species,
we must look beyond the exposure of the species to a factor to evaluate
whether the species may respond to the factor in a way that causes
actual impacts to the species. If there is exposure to a factor and the
species responds negatively, the factor may be a threat and we attempt
to determine how significant a threat it is. The threat is significant
if it drives, or contributes to, the risk of extinction of the species
such that the species warrants listing as endangered or threatened as
those terms are defined in the Act.
Factor A. The present or threatened destruction, modification, or
curtailment of its habitat or range
Habitat Loss
The Bay Institute has estimated that intertidal wetlands in the
Delta have been diked and leveed so extensively that approximately 95
percent of the 141, 640 hectares (ha)(350, 000 acres(ac)) of tidal
wetlands that existed in 1850 are gone (The Bay Institute 1998, ch. 4,
p. 17), and that 90 percent of the riparian forest and riparian
wetlands of the Sacramento Valley have been cleared, filled, or
otherwise eliminated. Diking, dredging, filling of wetlands, and
reduction of freshwater flows through more than half of the rivers,
distributary sloughs, and the Estuary for irrigated agriculture and
urban use have widely reduced fish habitat and resulted in extensive
fish losses (Moyle et al. 1995, p. 166-168). San Joaquin River flows
have been degraded to a higher extent than flows in the Sacramento
River (Feyrer et.al. 2007a, p. 1396).Limited spawning can take place in
river and stream habitats, but the persistence of the splittail is now
dependent on seasonal floodplains including the Yolo and Sutter
bypasses and Cosumnes River.
Loss and degradation of shallow, near-shore habitat is a historic,
current and future threat to the splittail. Riparian and natural bank
habitats are features that historically provided splittail with
spawning substrate, organic material, food supply, and cover from
predators. Vast stretches of the Sacramento and San Joaquin Rivers,
their tributaries, and distributary sloughs in the Delta have been
channelized and much of the shallow nearshore habitat has been leveed
and riprapped. The prevention of channel meandering by the placement of
riprap is causing a continual loss of low
[[Page 62077]]
velocity shallow water breeding habitat (Feyrer et. al. 2005, p. 167).
Beneficial Actions Offsetting Adverse Effects
While habitat loss has occurred, a number of habitat restoration
actions are also being undertaken.
CALFED Habitat Restoration:The CALFED Bay Delta Program (CALFED)
leadership has recently transitioned from the CALFED Bay Delta
Authority to the Bay Delta Stewardship Council. This changed the name
and governing structure of the program, but did not change the 2000
Record of Decision (ROD) for CALFED or any goals or objectives of the
CALFED plan.
The CALFED plan exists as a multi-purpose (water supply, flood
protection, and conservation) program with significant ecosystem
restoration and enhancement elements, The program brought together more
than 20 State and Federal agencies to develop a long-term comprehensive
plan to restore ecological health and improve water management for all
beneficial uses of the Bay-Delta system. The plan specifically
addresses ecosystem quality, water quality, water supply, and levee
system integrity.
The CALFED Ecosystem Restoration Program (ERP) presented a
strategic plan for implementing an ecosystem-based approach for
achieving conservation targets (CALFED 2000a, pp. 1-3). The CDFG is the
primary implementing agency for the ERP. The goal of ERP to improve the
conditions for the splittail will remain whether the splittail is
listed as threatened or endangered or not listed. In the CALFED
process, the splittail's status could be adversely affected by program
elements to: Increase water storage in the Central Valley upstream of
the Delta; modify Delta hydrologic patterns to convey additional water
south, and upgrade and maintain Delta levees. However, as noted
previously CALFED has an explicit goal to balance the water supply
program elements with the restoration of the Bay-Delta and tributary
ecosystems and recovery of the splittail and other species. Because
achieving the diverse goals of the program is iterative and subject to
annual funding by diverse agencies, CALFED has committed to maintaining
balanced implementation of the program within an adaptive management
framework. Within this framework of implementation, it is intended that
the storage, conveyance, and levee program elements would only be
implemented in such a way that the splittail's status would be
maintained and eventually improved.
CALFED has identified 29 specific species enhancement conservation
measures for splittail (CALFED 2000b. There are more than 150 projects
that benefit the splittail or its habitat in the plan and more than
half of those have been completed to date (2010 ERP database
spreadsheets). Key accomplishments of the ERP include investments in
fish screens, temperature control, fish passage and habitat protection
and restoration (CALFED 2007, p. 2).
Additional projects such as Cosumnes River floodplain restoration
and Liberty Island restoration are ongoing. Major obstacles to the
completion of these projects , especially the acquisition of land have
been overcome. Although discussion of all 150 programs currently
benefitting splittail will not be practical in this document, we have
highlighted several projects that have played an important role in
offsetting threats to the splittail into the foreseeable future.
Liberty Island lies at the southern end of the Yolo bypass. After
years of active agricultural production on Liberty island, the levees
were breeched in 1997 and the island was allowed to return to a more
natural state (Wilder 2010, PowerPoint s. 4). The CALFED program funded
the purchase of the island in 1999 by granting money to the Trust for
Public Lands for the acquisition of the island (Wilder 2010, PowerPoint
s. 5). Splittail are utilizing the flooded island and have been
documented in a number of surveys including the beach seine survey in
which they were the most abundant fish caught from August 2002 to July
2003 (Wilder 2010, PowerPoint s. 22; Liberty Island Monitoring Program
2005, p. 37; Marshall et al. 2006, p. 1). Splittail are utilizing the
southern portion of the island more than the northern portion of the
island (Webb 2009, p. 1). In 2007, the Delta Juvenile Fish Monitoring
program was awarded $2.5 million from the CALFED program for the Breach
III study at Liberty Island. Work has been initiated and results will
assist agencies in understanding the ecological system and developing
recommendations for future restoration projects (Hrodey 2008). There
are currently plans to remove additional levees by Wildlands
Corporation which has acquired a portion of Liberty Island that it
plans to return to natural floodplain habitat. Wildlands Corporation's
actions may be approved and initiated within the next year, but cannot
be counted as a conservation measures at this time (Roper 2010, pers.
comm.). When these actions are implemented, they are expected to
further increase splittail spawning grounds on Liberty Island.
Restoration efforts have also been undertaken at the Cosumnes River
Preserve (hereafter referred to as the Preserve) under management of
the Bureau of Land Management (BLM), The Nature Conservancy, and a
number of other agencies and private organizations. Restoration
activities that benefit splittail include riparian enhancement and
intentional breaching of levees to restore floodplain function. The
Preserve opened 81 ha (200 acres) to flooding in October of 1995 by
removing a 15.2 m (50 ft) section in a levee along the Cosumnes River
(Cosumnes River Preserve Management Plan March 2008). Following floods
in 1995 and 1997, the decision was made by the Preserve in coordination
with the U.S. Army Corps of Engineers to not repair the portions of the
levees breeched by the floods thus allowing for a more natural flood
regime (Cosumnes River Preserve Management Plan March 2008, ch. 2 pp.
6-7). Levees have been breached in a total of five locations to allow
flooding of a variety of habitats including marshes and sloughs (Crain
et al. 2004, p. 126). Restoration is ongoing and splittail are likely
to benefit from these efforts, as the area has also been described as
among the most important floodplain habitats still available to the
species (Moyle et al. 2004, p. 17). Splittail used the Preserve
floodplains during both years of a study conducted in 1999 and 2001
(Crain et al. 2004, p. 140). Splittail larvae were present in 2001 when
only a small portion of the floodplain in the study area was inundated.
Although spawning was not observed, it is presumed to have occurred in
the last week of March or the first week of April since larvae appeared
shortly after. Larvae moved off the floodplain during cold-water flow
pulses in the last week of April and the first week of May (Crain et
al. 2004, p. 140).
Other Habitat Restoration Projects:
The Yolo Bypass Wildlife Area (Wildlife Area), located within the
Yolo Bypass, currently encompasses 6,787 ha (16,770 ac). This area has
increased substantially since CDFG's original acquisition of
approximately 1180 ha (2,917 ac) in 1991. The added area has allowed
restoration actions that benefit splittail spawning efforts to proceed
by creating new seasonal floodplains (Yolo Bypass Wildlife Management
Land Management Plan, 2008, ch.1).
In early 2002, the Sacramento River National Wildlife Refuge
Complex (SRNWRC) began implementation of a Plan for Proposed
Restoration Activities on the Sacramento River National Wildlife
Refuge. The restoration
[[Page 62078]]
activities have resulted in the reestablishment or enhancement of 1707
ha (4, 218 ac) of the SRNWRC (Silveria 2010, pers. comm.). This
restoration is expected to benefit splittail through improvement of
vegetative conditions on floodplains. Restoration and enhancement
involve the removal of crops, orchards, and related infrastructure
(pumping units, barns, sheds, etc.) followed by replacement with native
vegetation appropriate to each site. In addition to restoration
efforts, levees have been removed at the Flynn and Rio Vista units and
a levee has been breached at the La Barracna unit (Silveira 2010, pers.
comm.). These efforts allow for a more natural floodplain regime and
increase native vegetation that benefits splittail.
Summary of Factor A
Rip-rapping of river and stream habitat constitutes a potential
threat to the Sacramento splittail. The implementation and magnitude of
the CALFED, Central Valley Project Improvement Act (CVPIA) (discussed
under Factor D) and other habitat restoration activities, which focus
on the restoration of habitats that directly and indirectly benefit
splittail go far beyond any foreseeable future habitat losses. The
overall effect of habitat restoration activities is also expected to
continue to be beneficial for splittail into the future.
Efforts undertaken in the past decade have benefited the species by
restoring its habitat. There is presently sufficient habitat to
maintain the species, and inundation frequency and duration in key
areas is sufficient to provide spawning to maintain the species.
Furthermore, habitat restoration activities that have been completed
are currently being implemented and those planned for the future are
adding to the available habitat for the species.
We conclude that the best scientific and commercial information
available indicates that the Sacramento splittail is not now, or in the
foreseeable future, threatened by the present or threatened
destruction, modification, or curtailment of its habitat or range.
Factor B. Overutilization for commercial, recreational, scientific, or
educational purposes
Recreational Fishing
Splittail were historically abundant enough to be harvested by
Native Americans and commercial fisheries, although no studies on
abundance were begun until 1963 (Moyle et. al. 2004, p. 7). Today,
splittail are harvested for bait by the sport fishery and as a food
source, but take is limited by the California Fish and Gave Commission
to two individuals per day as further discussed under Factor D. The
largest splittail may be the first to engage in the spawning migration
(Caywood 1974; Moyle et al. 2004, p. 15). The early-season fishery
potentially targets and removes females with high reproductive
potential. The effect of this fishery in the Sacramento River may be
relatively greater in dry years, when splittail spawning is largely
confined to river margins where fishing effort is concentrated.
Splittail is known to be an effective bait fish for striped bass and is
commonly caught by anglers for this use (Moyle et al. 2004, p. 19). The
splittail fishery is the smallest fishery targeted in the CDFG angler
survey (SFRA 2008). At present, there is no evidence of any trend in
the available data suggesting that larger fish are being
disproportionally removed from the population or that the size
structure of the splittail population has been altered by this small
fishery. There is no indication that the intensity of fishing or bag
limits will increase in the future.
Scientific Collection
Monitoring surveys conducted throughout the year, including the
Fall Mid-Winter Trawl (FMWT), Summer Tow Net Survey (TNS), Beach Seine
Survey, Chipps Island Trawl, Suisun Marsh Survey, and Spring Kodiak
Trawl Survey (SKT) capture and record adult and juvenile splittail.
These surveys sometimes result in the unintentional mortality of some
individuals. Data from the last 12 years of surveys conducted by the
Service are in Table 3.
Table 3. Take (collection and release) and mortality by U. S. Fish and
Wildlife Service surveys for 1999- 2010.
------------------------------------------------------------------------
Survey Number Taken Mortality
------------------------------------------------------------------------
Chipps Island 6887 339
------------------------------------------------------------------------
Mossdale 146,854 1,856
------------------------------------------------------------------------
Service Beach Seine 207,137 2,394
------------------------------------------------------------------------
An average of 383 splittail are killed every year in the course of
conducting Service surveys. Adult splittail spawn up to 100,000 eggs
per individual per fecundity event and the loss of a few thousand
individuals from scientific collection over a 10 year period is not
expected to have a significant effect at the population level. We have
no information to indicate use of the species for other commercial,
recreational, scientific, or educational purposes.
Summary of Factor B
The new CDFG regulation enacted in March 2010 limiting take of
splittail to two individuals per day has eliminated any potential
threat that fisheries may have posed. The best available scientific and
commercial data shows that this current level of take does not
adversely affect the splittail population or that this level of
mortality will increase in the future.
Annual Service surveys result in an average of 383 splittail being
killed each year. However, due to the high fecundity rate of splittail,
the average yearly loss has not had a significant effect at the
population level and the information obtain from the surveys is being
used to monitor the splittail populations.
We conclude that the best scientific and commercial information
available indicates that the Sacramento splittail is not now, or in the
foreseeable future, threatened by the overutilization for commercial,
recreational, scientific or educational.
Factor C. Disease or predation
Disease
The south Delta is fed by water coming from the San Joaquin River,
where pesticides (e.g., chlorpyrifos, carbofuran, and diazinon), salts
(e.g., sodium sulfates), trace elements (boron and selenium), and high
levels of total dissolved solids are prevalent due to agricultural
runoff (64 FR 5963, February 8, 1999). Of specific concern are the
threats posed by heavy metals such as mercury, selenium, and
pesticides. There is some possibility
[[Page 62079]]
that disease in splittail could be a function of increased contaminant
loading and subsequent immune system depression. Disease related to
contaminants is further discussed under Factor E below.
Splittail naturally carry parasites like most fish, but the effects
of parasites such as anchor worms manifest primarily when fish are
already stressed from other causes such as spawning (Moyle et al. 2004,
p. 19). Post-spawn adult splittail and male fish in particular, are
substantially weakened when migrating back to the estuary. We found no
information to indicate disease is a threat to the species. We
therefore, conclude that the best scientific and commercial information
available indicates that disease does not constitute a significant
threat to splittail now or in the foreseeable future.
Predation
Predators of splittail include striped bass (Morone saxatilis),
largemouth bass (Micropterus salmoides), and other native and non-
native piscivores (Moyle 2004, p. 18). In the past, we have considered
threats of predation to be minor because striped bass had coexisted
with splittail for decades and because CDFG stopped hatchery rearing
and release of striped bass in 2001 (59 FR 862, 64 FR 5963). Striped
bass populations have undergone a substantial decline starting in the
mid 1980's shortly after the overbite clam was introduced (Kimmerer et
al. 2008, p. 84). Furthermore, they are just one example of the many
species impacted by the larger Pelagic Organism Decline (POD) that
began in the beginning of the new millennium (Ballard et al. 2009, p.
1). Changes in the foodweb, toxic effects, export pumping and lowered
habitat quality are all potential causes of the POD. If non-native
striped bass populations increase, all size classes of splittail could
be under greater threat of predation. However, as stated above, striped
bass populations are in decline.
In contrast to striped bass, the abundance of largemouth bass has
increased substantially in the Delta in the past three decades (Brown
and Michniuk 2007, p. 195; Nobriga 2009, p. 112). The evidence suggests
that largemouth bass have taken advantage of the proliferation of
submerged vegetation throughout much of the Delta and the increasing
water clarity that has come with it (Brown and Michniuk 2007, p. 195).
Although, largemouth bass are a greater source of splittail mortality
than they were several decades ago, populations of largemouth bass in
critical rearing areas are low and predation levels appear to be minor.
Also, the high reproductive nature of splittail life history has
enabled it to overcome the predation that is occurring from largemouth
bass.
Based on a review of the best scientific and commercial information
available, we find that predation is not a significant threat to the
splittail now or in the foreseeable future.
Summary of Factor C
We found that disease occurs at low levels in the population, but
does not constitute a significant threat to the species. Predation by
striped bass appears to be unchanged from past levels. It is currently
not a significant threat to splittail populations and is not expected
to increase in the future. Largemouth bass populations have increased
in the Estuary in the past three decades, but populations of largemouth
bass in critical rearing areas are low, and therefore predation levels
appear to be minor. We conclude that the best scientific and commercial
information available indicates that the Sacramento splittail is not
now, or in the foreseeable future, threatened by disease or predation.
Factor D. The inadequacy of existing regulatory mechanisms
State Laws
The Porter Cologne Water Quality Control Act establishes the State
Water Resources Control Board (SWRCB) and nine Regional Water Quality
Control Boards that are responsible for the regulation of activities
and factors that could degrade California water quality and for the
allocation of surface water rights (California Water Code Division 7).
In 1995, the SWRCB developed the Bay-Delta Water Quality Control Plan
to establish water quality objectives for the Delta. This plan is
implemented by Water Rights Decision 1641, which imposes flow and water
quality standards on State and federal water export facilities to
assure protection of beneficial uses in the Delta (FWS 2008, pp. 21-
27). The various flow objectives and export restraints are designed, in
part, to protect fisheries. Objectives that benefit splittail by
increasing water availability and in turn available habitat include
specific outflow requirements throughout the year, specific water
export restraints in the spring, and water export limits based on a
percentage of estuary inflow throughout the year. The water quality
objectives are designed to protect agricultural, municipal, industrial,
and fishery uses; they vary throughout the year and by the wetness of
the year.
Assembly Bill (AB) 360, the State Delta Flood Protection Act, has a
primary purpose of strengthening Delta levees with various ``hard'``
structures, including rip-rap. Habitat restoration components of AB
360, considered mitigation for concurrent State projects' impacts to
aquatic and terrestrial ecosystems in the Delta, require improvement
rather than a strict mitigation approach which results in an increased
habitat benefit and a net increase in habitat.
The State Senate Bill (SB) 1086-funded Sacramento River
Conservation Area Forum is an interagency group chartered to promote
and guide protection and enhancement of riparian resources and fluvial
function along the reach of the lower Sacramento River between Red
Bluff and Colusa. The Nature Conservancy, working with the Sacramento
River Conservation Area and local stakeholders, has restored more than
1214 ha (3,000 ac) to date (The Nature Conservancy Website, Sacramento
River, 2010). These restoration efforts have replaced farmland with
potential splittail spawning and rearing habitat.
California Environmental Quality Act (CEQA)
The California Environmental Quality Act (CEQA) requires review of
any project that is undertaken, funded, or permitted by the State of
California or a local government agency. If significant effects are
identified, the lead agency has the option of requiring mitigation
through changes in the project or to decide that overriding
considerations make mitigation infeasible (CEQA Sec. 21002). In the
latter case, projects may be approved that cause significant
environmental damage, such as destruction of listed endangered species
or their habitat. Protection of listed species through CEQA is,
therefore, dependent on the discretion of the lead agency. The CEQA
review process ensures that a full environmental review is undertaken
prior to the permitting of any project within splittail habitat.
Streambed Alteration
Section 1600 of the California Fish and Game Code authorizes CDFG
to regulate streambed alteration. The CDFG must be notified of and
approve any work that substantially diverts, alters, or obstructs the
natural flow or substantially changes the bed, channel, or banks of any
river, stream or lake. If an existing fish or wildlife resource
including the splittail may be substantially adversely affected by a
project, CDFG must submit proposals to protect the species to the
person
[[Page 62080]]
proposing to alter the streambed within 60 days (Section 1602 of the
California Fish and Game Code).
Federal Laws
National Environmental Policy Act: The National Environmental
Policy Act (NEPA) (42 U.S.C. 4321 et seq.) requires all federal
agencies to formally document, consider, and publicly disclose the
environmental impacts of major federal actions and management decisions
significantly affecting the human environment. NEPA documentation is
provided in an environmental impact statement, an environmental
assessment, or a categorical exclusion, and may be subject to
administrative or judicial appeal. However, the Federal agency is not
required to select an alternative having the least significant
environmental impacts, and may select an action that will adversely
affect sensitive species provided that these effects are known and
identified in a NEPA document. Therefore, we do not consider the NEPA
process in itself to be a regulatory mechanism that is certain to
provide significant protection for the splittail.
Central Valley Project Improvement Act:The Central Valley Project
Improvement Act (CVPIA) (Public Law 102-575) signed October 30, 1992,
amends previous authorizations of the Central Valley Project (16 U.S.C
695d-695j) to include fish and wildlife protection, restoration, and
mitigation as project purposes having equal priority with irrigation
and domestic water supply, and fish and wildlife enhancement having
equal priority with power generation (Public Law 102-575, October 30,
1992).
Clean Water Act: The Clean Water Act (33 U.S.C. 1251 et seq.),
established in 1977, is the primary federal law in the United States
governing water pollution. The Environmental Protection Agency (EPA)
which is responsible for administering the Clean Water Act has given
the responsibility of issuing a ``303 list'' (impaired water body list)
to the respective Regional Water Quality Control Board that has
jurisdiction over the particular water bodies. Water bodies that do not
meet applicable water quality standards are placed on the section
303(d) list of impaired water bodies and the State is required to
develop a Total Maximum Daily Load Limit for the water body (TMDL). A
TMDL is a calculation of the maximum amount of a pollutant that a water
body can receive and still meet water quality standards.
San Joaquin Drain TMDL for Selenium
As discussed under Factor E, selenium has negative effects on
splittail. The following paragraph discusses the regulatory mechanism
in place to reduce selenium input into the Estuary. Selenium total
maximum daily load limits have been established by the California
Regional Water Quality Control Board (Waste Discharge requirement 5-01-
234 2001, p. 12) for selenium discharged from the San Luis Drain.
Selenium load limits are determined by wet or dry year classes and
limits were incrementally lowered from 2994 kilograms (kg) (6600 pounds
(lbs)) in 1996-1997 to 1604 kg (3236 lbs) in 2007-2008 (United States
Bureau of Reclamation (USBOR) 2009, pp. 1-5). Following the
implementation of these limits, selenium discharged from San Luis Drain
was reduced from 3175 kg (7000 lbs) in 1996-1997 to 791 kg (1744 lbs)
in 2007-2008 (USBOR 2009, pp. 1-5)). Although this will have limited
immediate effect on reducing selenium concentrations in splittail
habitat, it is a protective measure that will have a long-term effect
on reducing selenium loads in the Estuary and reducing or stabilizing
the threat of selenium to splittail in the future.
Lack of Total Maximum Daily Limits on contaminants at Wastewater
Treatment Plants
As discussed under Factor E, ammonia has negative effects on
splittail. The following paragraph discusses the lack of regulatory
mechanism acting to reduce ammonia input into the Estuary. The
Sacramento Regional Wastewater Treatment Plant SRWTP is responsible for
90 percent of the total ammonia load released into the Delta. Monthly
loads of ammonia from the SRWTP released into the Sacramento River
doubled from 1985 to 2005. Approximately 598 million liters (158
million gallons) per day were discharged from the SRWTP from 2001 to
2005 (Jasby et al. 2008, p. 15).
There are currently no regulations or limits on the amount of
ammonia being discharged by waste water treatment plants that discharge
into the Delta. The lack of Clean Water Act mechanisms limiting ammonia
discharged from these plants constitutes a low magnitude threat to the
splittail population. However, the EPA is currently updating freshwater
ammonia criteria on ammonia discharged from the SRWTP (EPA 2009, pp. 1-
46). On December 30, 2009 (74 FR 69086), the EPA announced the
availability of draft national recommended water quality criteria for
ammonia for the protection of aquatic life entitled, ``Draft 2009
Update Aquatic Life Ambient Water Quality Criteria for Ammonia--
Freshwater.'' The EPA accepted public comments on that draft document
until April 1, 2010 (75 FR 8698, February 25, 2010). The EPA is
currently reviewing the comments and expects to begin enforcement of
the criteria within 12 months. Ammonia and its detrimental effects on
the splittail population are discussed under the contaminants section
under Factor E.
California Fish and Game Commission Take Limit
The State of California Fish and Game Commission reduced a
potential threat to splittail on March 1, 2010, when a new harvest
limit on splittail was enacted through the addition of section 5.70 to
Title 14 of the California Code of Regulations (CDFG2010, p. 1). CDFG
now limits the take of splittail species to two individuals per person
per day. Secondary data collected during creel surveys for salmon and
striped bass suggest that in the past, a total catch of hundreds of
adult fish may have been caught on a daily basis (Moyle et. al. 2004,
pp. 6-13). The creel limit has reduced the impact of fishing on
splittail.
Summary of Factor D
Federal and State regulations described above provide protection
for the splittail and its habitat by limiting adverse affects from new
projects, restoring habitat and limiting contaminants discharged into
the Estuary. We acknowledge however that steps are currently being
taken by the California Central Valley Regional Water Quality Control
Board to enact new revised criteria on the ammonia that is discharged
from the SRWTP. Ammonia may be affecting individuals within the
population as discussed under Factor E, but we have no evidence that
the current lack of regulatory mechanisms limiting ammonia discharges
are having a significant population level effect on the splittail.
We conclude that the best scientific and commercial information
available indicates that the Sacramento splittail is not now, or in the
foreseeable future, threatened by inadequate regulatory mechanisms.
Factor E. Other natural or manmade factors affecting its continued
existence
We have identified the risk of water export facilities,
agricultural and power plant diversions, poor water quality,
environmental contaminants, climate change and introduced species as
[[Page 62081]]
potential threats to the Sacramento splittail.
Water Export Facilities
The Central Valley Project (CVP) was devised to tame the flood
waters of the Sacramento River and provide irrigation water for the
Central Valley of California. The project today includes 20 dams, 800
km (500 mi) of aqueducts and up to 8.6 kilometers cubed (km\-3\) (7
million acre-feet (maf)) of water exported annually for agriculture,
wildlife and urban uses (USBR Central Valley Project, 2009). The CVP's
Jones Pumping Plant consists of five pumps with a permitted diversion
capacity of 130 cubic meters per second (cms) (4, 600 cubic feet per
second (cfs)). The pumping plant raises water into the Delta-Mendota
Canal, which supplies water to much of the San Joaquin Valley. This
intricate system of water diversion and storage has changed the
historical hydrological features of the watershed systems and affected
the many species that are dependent on them including the splittail.
Reservoir and flood control operations inadvertently drain shallow
water spawning habitat along river corridors and exacerbate stranding
of splittail. Operations of Shasta and Trinity Dams and water
diversions including the Tehama-Colusa, Corning, and Glenn Colusa
canals, and the Red Bluff diversion dam further reduce instream flows.
These reductions in water flow have resulted in the elimination of
large tracts of spawning habitat for the splittail. Furthermore, dams
may have reduced the distribution of the splittail by restricting
movement to potential spawning grounds and creating migration
obstacles. These dams and diversions have altered and eliminated
habitat for splittail, and have on-going affects.
The State Water Project (SWP) consists of a network of dams,
reservoirs, canals and diversion facilities. Oroville Dam, on the
Feather River, and Lake Oreville, have a maximum operating storage of
3,537,580 acre-feet. The Banks Pumping Plant has a capacity of 291 cms
(10,300 cfs), which is effectively limited by regulation to 203 cms
(7,180 cfs). Water is conveyed via the Old and Middle River channels,
resulting in a net (over a tidal cycle or tidal cycles) flow towards
the pumping plants. When combined State and Federal water exports
exceed San Joaquin River inflow, the additional water is drawn from the
Sacramento River through the Delta Cross Channel, Georgiana Slough and
Three-Mile Slough. Combined flow in Old and Middle Rivers is referred
to as ``OMR'' flows while flow in the lower San Joaquin River is
referred to as ``QWEST.''
Four major water diversion facilities exported between 4.85 and 8.7
km\3\ (3.93 and 7.05 maf per year from the Delta during the years 1995
through 2005 (Kimmerer and Nobriga 2008, p 2). Of these, the State and
Federal facilities exported between 4.7 and 8.4 km\3\ (3.81 and 6.81
maf) averaging 7 km\3\ (5.7 maf) every year (DWR 2010b, p. 10). The
Barker Slough Pumping Plant, with a capacity of 175 cfs, diverts water
from the Barker Slough, south of the city of Dixon, into the North Bay
Aqueduct for delivery to Napa and Solano Counties. Each of the ten pump
bays is screened to exclude fish one inch or larger. The Old River
intake for the Contra Costa Water District is located on Old River near
State Route 4. It has a positive-barrier fish screen and a pumping
capacity of 250 cfs. It supplies water to Contra Costa Canal and to Los
Vaqueros Resovoir for use in the East Bay area.
The State Water Resources Control Board's revised Decision 1641
established an expert-to-inflow operational objective that allow the
SWP and CVP pumps to divert from 35 percent to 65 percent of the Delta
inflow (SWRCB 2000). From July through January, the objective is 65
percent and from February through June, the objective is 35 percent, to
protect fish and wildlife beneficial uses. The State Board also
established additional water quality objectives that may further limit
export pumping. Both pumping stations are equipped with their own fish
collection facilities that divert fish into holding pens using louver-
bypass systems to protect them from being killed in the pumps.
Operation of the CVP and SWP water export facilities directly
affects fish by entrainment into their diversion facilities. Splittail
are relocated if entrained. These salvaged fish are then loaded onto
tanker trucks and returned to the western Delta downstream (Aasen 2009,
p. 36). The movement of fish can result in mortality due to stress,
moving procedures, or predation at locations where the fish are moved
too. It is unknown how many fish survive this process, but mortalities
could be high due to overcrowding in the tanks and predation at drop-
off points. Splittail females migrating upstream to spawn are
transported back downstream by truck if entrained and could potentially
be forced to start their migration again. It is speculated that this
could result in their removal from the spawning population for that
year (Moyle et al. 2004, p. 20).
The fish collection facilities entrain a great number of splittail
in hydrologically wet years (approximately 5 million splittail in 1995,
3 million in 1998 (Moyle et al. 2004, p 21), and 5.5 million in 2006
(Aasen 2007, p. 49)) when spawning on the San Joaquin River and other
floodplains results in a spike in population numbers. However,
entrainment is low during hydrologically dry years when recruitment is
low (1,300 splittail in 2007 (Aasen 2008, p. 55) and about 5,000 in
2008 (Aasen 2009, p. 43)). These figures show the high annual
variability of reproductive success. Research has shown no evidence
that south Delta water exports have a significant effect on splittail
abundance although that does not mean that entrainment never affects
the species (Sommer et al. 2007, p. 32). Most entrained individuals
tend to be young of the year migrating to optimal downstream rearing
habitat, although some migrating adults do get entrained (Sommer et al.
1997, p. 973). If distribution of age 0 individuals was to shift toward
the export pumps in a dry year with low reproductive output, there
could be substantial effect on that year-class (Sommer et al. 1997, p.
973). However, this would only constitute a potential threat to that
particular year class and still does not represent a significant threat
to the overall population since it would occur only during a dry year.
The pumping facilities do not represent a significant threat to the
splittail because loss of substantial number of fish tends to occur
during wet years in which the species is experiencing a high
reproductive output.
Agricultural Diversions for Irrigation
Fish including splittail can become entrained in agricultural water
diversions. This entrainment can result in injury or mortality. The
diversion of water flows by agricultural pumping can also alter natural
flow regimes and impede migration. Screening of agricultural diversions
has been a common practice in recent years in order to conserve and
restore populations of anadromous fishes in the Central Valley of
California. There are over 3,700 diversions on the Sacramento and San
Joaquin Rivers and their tributaries, and the Sacramento-San Joaquin
Delta and Suisun Marsh. Over 2,300 of these diversions are located in
the Sacramento-San Joaquin Delta, with over 350 in Suisun Marsh. Of
these 3,700 existing diversions, over 95 percent are currently
unscreened (CDFG 2010).
[[Page 62082]]
Under both the CALFED Bay-Delta Program and the Central Valley
Project Improvement Act there have been significant efforts to screen
agricultural diversions in the Central Valley and the Sacramento-San
Joaquin Delta, particularly the larger unscreened diversions over 4.24
cms (150 cfs) on the Sacramento River. Entrainment of splittail at
diversions is reduced if fish screens are installed at diversions
within splittail habitat areas.
Currently, all of the unscreened diversions on the Sacramento River
main stem over 4.24 cms (150 cfs) have been screened or are currently
proposed to be screened. There are a number of large unscreened
diversions over 4.24 cms (150 cfs) on the San Joaquin River. Many of
these larger diversions will be considered for screening as part of the
San Joaquin River Restoration Program. The Sacramento-San Joaquin Delta
region is the location of the majority of unscreened diversions, with
most of these diversions under 1.41 cms (50 cfs) (Meier 2010, pers.
comm.).
CALFED's Ecosystem Restoration Program includes a program to
consolidate and screen the remaining small agricultural diversions in
the Delta, and the Sacramento and San Joaquin rivers. The NOAA
Fisheries Restoration Center has also begun to fund small fish screen
projects in the Sacramento River within the range of the splittail.
The amount of entrainment that may occur at the remaining
unscreened diversions is not well-known, and efforts to determine the
effect of entrainment on splittail have been limited. In July of 2001
and 2002, Nobriga et al. sampled fish entrained within a 61 cm (24 in)
diameter pipe at the CDWR Horseshoe Bend Diversion facility (Nobriga et
al. 2004, p. 1). They collected only one splittail during two sampling
periods, finding entrainment to be exceptionally low (Nobriga et. al.
2002, p. 35-44). 115, 000 m\3\ of water passing through an unscreened
diversion was sampled over a 69 hour period (Nobriga et al. 2004, pp.
1-16). Another study at the Morrow Island Distribution System showed
that the diversions there took 666 splittail young-of-the-year-
individuals, but only nine individuals of age one or older (Enos 2010,
p. 14). After sampling 2.3 million m\3\ (81.2 million ft\3\) of water,
it was concluded that entrainment of special status species including
the splittail was exceptionally low (Enos 2010, p. 17). In analyzing
these results, it is helpful to compare this take to the 5million to 6
million splittail that can be entrained at the south Delta water export
pumps in a single year. Research has shown no evidence that south Delta
water exports have a significant effect on splittail abundance (Sommer
et al. 2007, p. 32). Splittail adults can yield up to 100,000 eggs in a
single spawning event, therefore the loss of thousands or even a
million young-of-year is not expected to effect the longterm population
viability of the species. Furthermore, splittail may not be as
vulnerable to agricultural diversions as other fish species are because
adult splittail migrate during winter to early spring when agricultural
diversion operations are at a minimum.
We do not consider entrainment by agricultural diversions to be a
significant threat to splittail. Additionally, these effects from
agricultural diversions are expected to decrease in the future as
additional diversions continue to be screened.
Power Plant Diversions
Two power plants located near the confluence of the Sacramento and
San Joaquin rivers pose an entrainment risk to splittail: the Contra
Costa Power Plant and the Pittsburg Power Plant. The intakes for the
cooling water pumps of these power plants are located in close
proximity to splittail rearing habitat (Moyle et al. 2004, p. 20). The
maximum combined non-consumptive intake of cooling water for the two
facilities is 91.7 cms (3,240 cfs), which can exceed 10 percent of the
total net outflow of the Sacramento and San Joaquin rivers. Thermal and
chemical pollution in the forms of raised water temperature and
chlorine discharges may also have a detrimental effect on splittail
(USFWS 2008, pp. 173-174). However, power plant operations have been
substantially reduced since the 1970s, and the plants are now either
kept offline, or are operating at very low levels, except as necessary
to meet peak power needs. Due largely to this reduction in the
operation of the power plants and their associated pumping for cool
water, we do not consider the operation of these power plants to
constitute a significant threat to the splittail population. We have no
indications of future plans to use these pumps more frequently and
therefore, do not consider these operations to be a threat in the
future.
Water Quality and Environmental Contaminants
Although recent research funded by CALFED and carried out in a
large part by UC Davis has shed some light on the dynamics and impacts
of contaminants entering the Delta system, the overall effects of these
contaminants on ecosystem restoration and species health are still
poorly understood. All major rivers that are tributaries to the Estuary
are exposed to large volumes of agricultural and industrial chemicals
that are applied in the Central Valley watershed (Nichols et al. 1986,
pp. 568-569), as well as chemicals originating in urban runoff that
find their way into the rivers and Estuary. In addition, re-flooding of
the Sutter and Yolo Bypasses and the use of other flooded agricultural
lands by splittail for spawning can result in agricultural-related
chemical exposures.
A majority of the Delta has been placed on the Clean Water Act's
303d list of impaired waterbodies due to the documented presence of
polychlorinated biphenyls (PCBs), organophosphate pesticides, other
legacy pesticides, and some metals - particularly mercury (CVRWQCB
2006, pp. 5-11). These contaminants can have adverse effects on fish
(i.e., splittail), but the magnitude of effects are dependent upon: The
chemical form of the contaminant in question; the contaminant's
bioavailability under certain water quality parameters (i.e., hardness,
pH, etc.); the nature of the response being measured in the fish (acute
toxicity, bioaccumulation, reproduction, etc.); and the nature/status
of the individual fish (age, weight, health, etc.).
All life stages of splittail are potentially exposed to varying
amounts and mixtures of chemical contaminants in the Delta and
associated water bodies. Acid mine drainage has been a serious
environmental problem in the northern portion of the Sacramento River
Basin (Alpers et al. 2000a, p.4; b, p. 5). Several streams are listed
as impaired because of high concentrations of metals such as cadmium,
copper, lead, and zinc. Metals concentrations in previous years have
been toxic to fish in the upper Sacramento River near and downstream
from Redding (Alpers et al. 2000a, p 4; b, p. 5). Recent mitigation
efforts at one of the more contaminated sites in the Spring Creek
drainage near Shasta Lake have significantly lowered concentrations of
metals in the Sacramento River, and no toxic effects to fish were
observed during the course of this investigation (Alpers et al. 2000a,
p.3; b, p. 2). However, elevated levels of metals such as copper in
streambed sediment can still be measured in the upper Sacramento River
Basin downstream from Redding (MacCoy and Domagalski, 1999, p. 35).
Copper and other metals may still affect aquatic organisms in upper
portions of contributing watersheds of the Delta. However, five
potential contaminant threats have been identified as a
[[Page 62083]]
concern specifically with respect to the splittail: (1) selenium, (2)
mercury, (3) organophosphates, (4) pyrethroids, and (5) ammonium/
ammonia. A summary of each identified contaminant threat is provided
below. In part, these contaminant threats are of concern because they
may be focused, to varying degrees, on habitat features and biological
characteristics tentatively identified as particularly relevant to
splittail conservation.
Selenium
The primary risk posed by selenium is a direct result of its
propensity to cycle through the food web, its dominant exposure
pathway, and its ability to cause reproductive impairment in fish
(Lemly 1999, p. 150-151; Lemly 2002, p.47). The primary source of
selenium coming into the Delta system enters through the San Joaquin
watershed in the form of agricultural run-off via the San Luis Drain
(Luoma et al. 2008, p. 63). Recent studies on selenium toxicity in
aquatic food chains have generally reached the conclusion that a water-
based criterion is not suitable due to ``...temporal [and spatial]
changes in concentrations, speciation, and rates of transfer between
water, sediment and organisms...'' (Hamilton 2004, p. 8). Since the
primary route of exposure to selenium is via the diet, and selenium is
highly bioaccumulative, these differences can mean that a concentration
of selenium in water that results in adverse effects in one location
may not result in adverse effects to the same species in another
location. Thus, the current recommendation (USEPA 2004, p. 82; Chapman
2007, p. 21; Hamilton 2002, p. 95; 2004, p. 22) for the appropriate
media for regulation of selenium in the aquatic environment is not
water, but rather tissue.
To examine the potential adverse effect levels of selenium on
splittail, Teh et al. (2004, pp. 6085-6087) fed juvenile splittail
organic selenium for 9 months in the laboratory. From this experiment,
Teh et al. (2004, pp. 6087-6090) derived a no observed adverse effects
level (NOAEL) and lowest observed adverse effects level (LOAEL) for
deformities in juvenile splittail of 10.1 and 15.1 mg/kg-dry weight
(dw) in muscle tissue and 23.0 and 26.8 mg/kg-dw in liver tissue,
respectively. However, Rigby et al. (2010, p.77) performed a logistic
regression using data from Teh et al. (2004, pp. 6087-6090) to derive a
more precise estimate of the threshold for selenium toxicity in
splittail and derived EC10 values of 0.9 mg/kg-dw in feed,
7.9 mg/kg-dw in muscle, and 18.6 mg/kg-dw in liver for juveniles. The
derived EC10 values by Rigby et al. (2010, p. 79) represent
the predicted selenium concentration at which deformities would be
observed in 10 percent of the juvenile population.
In a laboratory setting, research by Teh et al. (2004, p. 6092) has
shown that the prevalence of deformities among juvenile splittail in
the laboratory increase at dietary concentrations greater than 6.6 mg/
kg-dw while concentrations of 26.0 mg/kg-dw and greater significantly
decrease body weight, total length, and condition factors of juvenile
splittail. This may be due to the liver's inability to metabolize and
excrete biochemicals due to its reaction to high selenium intake (Teh
et al. 2004, p. 6092).
In field settings, selenium concentrations analyzed from tissues of
adult splittail captured in the Suisun Bay/Marsh area show elevated
concentrations in muscle ranging from 4 to 5 mg/kg (5 ppm), and liver
concentrations ranging as high as 20 mg/kg (20 ppm) (Stewart et al.
2000, p. 1). The median selenium liver g/g-dwconcentrations in
splittail collected from Suisun Bay are about 13 (13 ppm) (Stewart et
al. 2004, p. 4523). Although deformities typical of selenium exposure
including lordosis (spinal deformities) have been observed in splittail
collected from Suisun Bay (Stewart et al. 2004, p. 4524), the known
data on muscle and liver concentrations in splittail adults are below
the EC10 values derived by Rigby et al. (2010, pp. 76-79).
Current threshold tolerances of selenium exposures by splittail may
be higher than other species that use upper portions of the water
column (Teh et al. 2004, pp. 6087-6090). However, laboratory and field
studies cited above lead us to conclude that although selenium is
considered elevated within the Delta, selenium exposures, although
important, are not having a significant population-level effect on the
species.
Bioaccumulation of selenium by splittail in the Estuary is a
potential concern because the diet of adult splittail consists of
bivalves (including Asiatic clam and overbite clam), amphipods,
cladocerans, harpacticoid copepods, mysids, and detritus (Moyle et al.
2004, p. 22). Asiatic and overbite clams are benthic filter feeders
that take up and accumulate selenium (Stewart 2004, p. 4522). The
relationship between the bioaccumulation of selenium in the overbite
clam and its predation by splittail may be significant because
subsequent to the clam invasion, splittail shifted their diet from prey
items such as estuarine copepods to a diet increasingly focused on
bivalves, in particular, overbite clams (Feyrer et al. 2003, p. 285).
The recent increased reliance of splittail on overbite clams as a
food source may be a risk factor for increased selenium accumulation in
splittail. Concentrations of selenium in overbite clams in the San
Francisco Bay Estuary rose three fold from the mid 1980's to 1997. Some
of this rise may have been a result of high run-off during the wet
years of 1995-1997 (Linville 2002, p. 56-59) when the survey was
concluding. In the San Francisco Bay, selenium concentrations in
Asiatic and overbite species range from 2 to 9 and 5 to 20 mg/kg-dw,
respectively (Stewart et al. 2004, p. 4522; Presser and Luoma 2006, p.
48) compared with other native diet items of amphipods and mysids which
range from 1 to 3 mg/kg-dw (Stewart et al. 2004, p. 4522). These
concentrations exceed the previously discussed dietary EC10
of 0.9 mg/kg-dw derived by Rigby et al. (2010, p.78). However, the
EC10 value developed by Rigby et al. (2010, p. 78) reflects
adverse effects upon juveniles from dietary exposures. In Suisun Marsh
adult splittail gut contents are predominantly detritus (Feyrer et al.
2003, p. 281). Feeding behavior of splittail in Suisum Marsh suggest
they are more dependent upon detritus food sources which would likely
expose them to lower concentrations compared of selenium to bivalve and
amphipod diet sources.
Moyle et al. (2004, p. 17) hypothesized that success of juvenile
downstream migration is strongly linked to the size that juvenile
splittail achieve prior to exiting the spawning areas. It was suggested
that a minimum size of 25 mm (1 in) greatly enhances success of
downstream migration. Moyle presented data demonstrating statistically-
significant declining growth rates. The apparent declines in growth
rates observed in Suisun Marsh splittail between 1980 and 1995 by Moyle
et al. (2004, p. 14) were correlated to the invasion of the Estuary by
the overbite clam, and the subsequent shift of splittail to an overbite
clam-dominated diet. Moyle et al. (2004, pp. 14-15) suggested that this
trend might reflect cachexia (contaminant-induced weight loss despite
calorically sufficient dietary intake) which is a classic symptom of
non-lethal selenium poisoning. However, Moyle et al. (2004, p. 30) also
suggested this decline in growth rates may reflect poorer energetics
from shifting to a non-mysid shrimp-dominated diet.
Steps have been taken to reduce the input of selenium into the
Estuary (see discussion under Factor D) and selenium loads discharged
from the San
[[Page 62084]]
Joaquin drainage have been reduced over the last decade. In addition,
the predominant source of selenium in the Delta (i.e., irrigation
drainage from the San Joaquin River watershed) is somewhat removed from
areas containing important spawning habitat for the species (Sacramento
River watershed). Furthermore, studies on the effects of the overbite
clam on splittail abundance have been inconclusive. Feyrer et al. found
that changes in the food web have had effects on the diets of older
splittail (2003, pp. 278-285), but Kimmerer found no evidence that the
splittail decline was directly related to the decline in opossum shrimp
(2002, pp. 51-52). Therefore, we have no conclusive scientific data
finding that the splittail growth rates are the result of any selenium
induced bioaccumulation mechanism. While there is scientific
information that indicates overbite clams do accumulate selenium, there
is no indication that the bioaccumulation of selenium in splittail as
the result of eating these bivalves has resulted in a population
decline of the species. Therefore, we conclude that selenium does not
constitute an immediate threat to the splittail through all or a part
of its range at this time or in the foreseeable future. However, the
potential long-term chronic threat that selenium may present to
splittail condition and health cannot be discounted when combined with
other potential water quality stressors and should be examined in more
detail in the future.
Mercury
The Sacramento River watershed was the site of significant mining
activity during the 19th century, including hard rock and hydraulic
gold mining (primarily in the Sierra Nevada), mercury mining in the
Coast Range (primarily to support gold mining), and hard rock mining
for copper, silver, and other metals in portions of the Sierras and
northern Coast Range. California's Coast Range represents one of the
world's five major mercury mining areas (Jasinski 1995, p. 151).
Historic hydraulic gold mining and gold dredging beginning in the
1850's in mountains upstream of the Delta set in motion a continual
stream of mercury flowing into the Estuary from the Sacramento
watershed that is still having residual effects today (Healy 2008, p.
23).
Analytical data indicate that mercury concentrations in aquatic
biota in the San Joaquin River are exceeding screening thresholds and
may pose ecological and human health risks (Davis et al. 2000, pp. 9-
16). Laboratory studies by Deng et al. (2008, p. 200-202) found dietary
mercury and a combination of mercury and selenium caused damage to
liver, kidney and gill tissue of splittail after four weeks of
exposure. Although liver glycogen depletion and kidney tubular dilation
were observed by the Deng et al. study, these lesions did not seem to
pose a direct threat to the survival of the splittail larvae (2008, p.
202). Because splittail require floodplain inundation to reproduce,
they need habitats like the Yolo Bypass and the Cosumnes River
floodplain. The reliance on these regions for reproduction creates a
potential risk for eggs and juveniles to be exposed to mercury
contamination. However, field studies regarding mercury toxicity to
splittail eggs and juveniles are lacking.
Regarding risks from bioaccumulation of mercury via the food chain
pathway, several research groups are currently addressing mercury
accumulation in the Delta food web. However, no systematic study exists
of mercury distributions in the food web of the Bay. Bioaccumulation
processes depend on the amount of mercury in surficial sediments, the
water quality at the sediment/water interface, and local food web
dynamics.
Methylmercury is the most important form of mercury in the aquatic
environment with regard to accumulation by biota and transfer through
the food web. Methylmercury is produced through addition of a methyl
group to Hg2+, a process referred to as methylation. The precise
mechanism for entry of methylmercury to the food chain is unknown.
However, this initial step is critical, because concentrations of
mercury in plankton can be about 10,000-fold higher than in water
(Krabbenhoft 1996, p. 2). After this initial step, methylmercury
concentrations increase approximately 0.5 log units per trophic level
(Watras and Bloom 1992, p.1316), suggesting that each successive
trophic level derives methyl-Hg from a progressively more concentrated
source (i.e. the previous trophic level), in a process known as
biomagnification. In this process consumers retain and further
concentrate much of the methylmercury of their prey and subsequently
pass this on to the next trophic level. Species at high trophic
positions in the aquatic food web, such as predatory fish, attain
concentrations that are approximately a million times higher than
concentrations in water. Because methylmercury biomagnifies, trophic
position is one of the primary factors influencing observed tissue
concentrations.
Given that splittail are fairly low in trophic status and feeding
guilds in the Estuary, the likelihood of accumulating and biomagnifying
mercury from the food web is low. One study has linked elevated mercury
to the Cosumnes River floodplain and the Yolo Bypass (Slotten et al.
2000, p. 44), which are both primary spawning grounds for splittail.
However, this study found no increased levels of mercury in lower
trophic level biota that occurred in these floodplains (Slotten et al.
2000, p. 44). Although laboratory studies have shown mercury to have
adverse effects to splittail individuals and there are increased risks
of mercury exposures in splittail spawning grounds, the Slotten study
did not find that these mercury levels transferred into the food web
and additional field studies regarding mercury toxicity to splittail
are lacking.
We have considered mercury as a possible threat to the splittail,
but there is limited information on the effects of mercury on splittail
population dynamics. Therefore we have determined that mercury and its
potential for bioaccumulation and/or biomagnifications does not
constitute a significant threat to splittail now or in the foreseeable
future.
Organophosphates
Organophosphate pesticides such as diazinon, chlorpyrifos, and
malathion are toxic at low concentrations to some aquatic organisms.
Several areas of the Delta, particularly the San Joaquin River and its
tributaries, are listed as impaired under the Clean Water Act due to
elevated levels of diazinon, chlorpyrifos, and other pesticides.
Organophoshates enter agricultural drainage mainly in stormwater runoff
because it is sprayed on orchards during the rainy winter season. The
environmental fate of chlorpyrifos and diazinon are not well
understood. Previous work shows that chlorpyrifos is adsorbed strongly
onto sediment particles, reducing the aqueous concentration (Karen et
al. 1998, p.1584). The fate of adsorbed chlorpyrifos is not known. For
chlorpyrifos dissolved in water, volatilization, photolysis, and
hydrolysis are major removal mechanisms (Howard, 1999; Racke, 1993).
The role of biodegradation in chlorpyrifos removal is not well
understood. Giddings et al. (1997) did find that the degradation of
chlorpyrifos in water followed a first-order decay model (p. 2360). The
environmental fate of diazinon is less known, but it is more soluble
than chlorpyrifos and undergoes pH-dependent decomposition in water
(Drufovka et al. 2008, p. 295).
[[Page 62085]]
Some species of zooplankton are affected by diazinon concentrations
as low as 0.35 [micro]g/L (Amato et al, 1992, p. 214). From 1988 to
1990, the Central Valley Regional Water Quality Control Board conducted
an aquatic toxicity survey in the San Joaquin Valley. Surface water
samples collected from certain reaches of the San Joaquin River
watershed during this survey were acutely toxic to the water flea,
Ceriodaphnia dubia (Foe and Connor 1991). The cause of toxicity was not
determined but was attributed to pesticides in general. Further study
was conducted in the Valley during the winter of 1991-92, and the
resultant toxicity was attributed to the presence of chlorpyrifos and
diazinon (Foe and Sheipline, 1993; Foe, 1995; Kuivila and Foe, 1995, p.
1149). Recognizing toxic concentrations of organophosphates can occur
in tributaries to the San Joaquin and Sacramento River when
agricultural areas contribute storm runoff, toxic concentrations rarely
occur in the Sacramento River itself (MacCoy et. al 1995).
Although organophosphate pesticides commonly used in agricultural
areas have been shown to be present in Delta waters and their
tributaries at concentrations toxic to aquatic organisms (Werner et al.
2000, p. 226), little is known about the sensitivity of Sacramento
splittail to these chemicals. Previous investigations of larval striped
bass (Morone saxatilis) in the Delta indicated many larvae had been
exposed to toxic compounds, potentially leading to slower growth and
increased mortality rates (Bennett et al. 1995). It is possible that
these contaminants also contribute to mortality and potentially affect
juvenile splittail recruitment. Teh et al. (2005) conducted 96-hour
acute toxicity tests on 7-day-old splittail larvae to determine the
level of toxicity of orchard runoff water containing organophosphorus
pesticides and observe potential biological effects. Spliital larvae
were then transferred to clean water for three months to assess the
survival, growth, histopathological abnormalities, and heat stress
proteins. The results of although splittail larvae survived the 96 h
exposure, Teh et al. (2005) observed exhibited reduced survival and
growth and showed signs of cellular stress even after a three month
recovery period.
Sublethal effects may play a more important role than acute
mortality, but there is a lack of studies to identify and quantify
sublethal responses to pesticides in splittail. In addition, although
several studies have demonstrated the acute and chronic toxicity of two
common dormant spray insecticides, diazinon and esfenvalerate, in other
fish species (Barry et al. 1995, Goodman et al. 1979, Holdway et al.
1994, Scholz et al. 2000, Tanner and Knuth 1996), little work has been
done integrating acute toxicity with biomarkers of exposure. Sublethal
exposure to insecticides is expected to cause a wide range of responses
(biomarkers) in individuals ranging from genetic to reproductive
anomalies. The addition of sublethal responses to routine acute
toxicity testing may provide advanced warning of potentially
significant environmental impacts and risks associated with
organophosphate pesticides and prevent underestimation of effects on
splittail populations. However, based upon the limited data available,
we do not consider organophosphates to be a significant threat to the
splittail population at this time. Although residual organophosphates
will continue to be present in the ecosystem and site specific
exposures will occur in localized areas that may affect individuals,
the reduction of organophosphates discharged into the Delta due to EPA
restrictions in recent years has greatly reduced the potential threat
that organophosphates may have posed in the past (Luoma 2008, p. 64).
Pyrethroids
Pyrethroid use in the Central Valley has steadily increased since
1991 and reached an annual use of 80, 740 kilograms (kg) (178,000
pounds (lbs)) in 2003 (Oros and Werner 2005, p 11). Many farmers have
switched from organophosphate-based insecticides to pyrethroid-based
insecticides (which adhere to soil more strongly) due to a decision by
the EPA to phase out organophosphates due to their toxicity to humans
(Luoma 2008, p. 64). Pyrethroids have a high absorption rate, andlow
water solubility; they rapidly absorb to soil and organic matter
(Werner 2004, p. 2719). Although pyrethroids bioaccumulate, food web
exposure is not considered a significant route of exposure to fish
(Hill 1985). The primary mode of transport for pyrethroids in aquatic
systems is the adsorption of pyrethroids to surfaces of clay and soil
particles that are suspended in the water column (Oros and Werner 2005,
p 24). This combination of properties lends itself to accumulation of
this substance in areas such as the Yolo Bypass.
All synthetic pyrethroids are potent neurotoxins that interfere
with nerve cell function by interacting with voltage-dependent sodium
channels as well as other ion channels, resulting in repetitive firing
of neurons and eventually causing paralysis (Bradbury and Coats 1989,
pp. 377-378; Shafer and Meyer, 2004). Pyrethroids are toxic to most
aquatic invertebrates and fish, in many cases more toxic than the
organophosphates they are replacing with LD50 values for aquatic
organisms below 1 ppb (Smith and Stratton, 1986). The LD50 is the dose
required to kill half the members of a tested population after a
specified test duration. Aquatic insects are more sensitive to
pyrethroids than fish, however, mollusks are relatively insensitive
(Clark et al., 1989). Acute effects of pyrethroids on aquatic insects
could reduce available food resources for splittail. However, the
magnitude of this potential effect is unknown and has not been studied.
Chronic exposures to pyrethroids can have significant impacts for
immune function, reproductive success and survival for fish and their
food organisms. Histopathological lesions in the liver were observed in
splittail shortly (1 week) after 96-hour exposure to sublethal
concentrations of organophosphate and pyrethroid insecticides. Fish
recovered from these lesions, but showed high (delayed) mortality
rates, grew slower and showed signs of cellular stress even after a 3
month recovery period (Teh et al. 2004b, p. 246).
Sub-lethal toxicity studies specific to splittail are limited but
data exists for other fish species. One pyrethroid, esfenvalerate,
exhibited both larval survival and immune effects in two fish species.
Delayed spawning and reduced larval survival of bluegill sunfish
(Lepomis macrochrius) were observed following two applications of 1 ppb
of esfenvalerate (Tanner and Knuth 1996, pp. 246-250). Exposures of
0.08 ppb esfenvalerate dramatically increased the susceptibility of
juvenile Chinook salmon (Oncorhynchus tshawytscha) to Infectious
Hematopoietic Virus (Clifford et al. 2005, pp. 1770-1771).
We conclude that although pyrethroids have been shown to have
potential chronic to sub-lethal effects on individuals, there is no
evidence to suggest that splittail exposures to pyrethroids in the
Estuary are having a significant effect at the population level.
Therefore we have determined that pyrethroids do not represent a
substantial threat to splittail now or in the foreseeable future.
Ammonium
The effect of ammonia on aquatic organisms depends on its form.
Ammonia is un-ionized, and has the formula NH3. Ammonium is ionized,
and has the formula NH4\+\. The major
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factors determining the proportion of ammonia or ammonium in water are
water pH and temperature. This is important as the unionized NH3 is the
form that can be toxic to aquatic organisms while NH4 is the form
documented to interfere with uptake of nitrates (NO3) by phytoplankton
(Dugdale et al. 2007, Jassby 2008). The chemical equation that drives
the relationship between ammonia and ammonium is:
NH3 + H2O [larr][rarr] NH4\+\ + OH-
When the pH is low, the reaction is driven to the right, and when
the pH is high, the reaction is driven to the left. When temperature is
high, the reaction is driven to the left and when temperature is low
the reaction is driven to the right. Ammonia enters the Delta ecosystem
through discharge from wastewater treatment plants, nitrogenous
fertilizers, and atmospheric deposition. The largest source of ammonia
entering the Delta ecosystem is the Sacramento Regional Wastewater
Treatment Plant (SRWTP), which accounts for 90 percent of the total
ammonia load released into the Delta. Monthly loads of ammonium from
the SRWTP released into the river have doubled from 1985 to 2005
resulting in 598 million liters (158 million gallons) per day
discharged from the SRWTP during 2001-2005 (Jasby et al. 2008, p. 15).
Ammonia can be toxic to aquatic organisms and its acute and chronic
effects are dependent on both pH and temperature. Ammonia is an oxygen
demanding substance requiring oxygen for nitrification and could
contribute to dissolved oxygen depletion in receiving waters. Effects
of elevated ammonia levels on fish range from irritation of skin,
gills, and eyes to reduced swimming ability and mortality (Wicks et al.
2002, p. 67). In addition to direct effects on fish, ammonia in the
form of ammonium may alter the food web by adversely impacting
phytoplankton and zooplankton dynamics in the Estuary ecosystem.
Ammonia can be toxic to several species of copepods important to larval
and juvenile fishes; ammonium may impair primary productivity by
reducing nitrate uptake in phytoplankton (Dugdale et al. 2007, pp. 27-
28).
A conceptual research framework has been prepared to improve
understanding of the role of anthropogenic ammonia in the Bay-Delta
ecosystem (Meyer et al. 2009, pp. 3-14). No studies to date address the
effects of ammonia on splittail specifically. However, concerns related
to synergistic effects from ammonia and other contaminants on splittail
and other fish species in the Sacramento River have been raised. One
study conducted at the University of California Davis Toxicology
Laboratory did not observe levels toxic to delta smelt, or two of its
food organisms, in the Sacramento River downstream of SRWTP. However,
treated effluent was found to be more chronically toxic than Sacramento
River water seeded with ammonium chloride to equal concentrations,
suggesting that additional toxicants are present in SRWTP effluent
(Werner 2009, p. 21).
EPA is currently updating freshwater ammonia criteria that will
include new discharge limits on ammonia (EPA 2009, pp. 1-46). There is
no projected date for its adoption but a National Pollution Discharge
Elimination System (NPDES) permit for the SRWTP is being prepared by
the California Central Valley Regional Water Quality Control Board for
public notice in the fall of 2010. The NPDES permit is expected to
include new ammonia limitations which will reduce loadings to the
Delta.
Although ammonia/ammonium is identified as a contaminant that is
likely having a negative impact on the Estuary and may chronically or
sub-lethally affect individual splittail within the population, there
is no evidence that ammonia is having a population level effect on the
species or will in the foreseeable future.
Summary of Contaminants
Most fish including splittail can be especially sensitive to
adverse effects in their larval or juvenile stages when exposed to
contaminants. Given splittail biology, adverse effects would be more
likely to occur where sources of contaminants occur in close proximity
to spawning and /or rearing habitats (i.e., floodplains, rivers and
tributaries). Splittail are benthic feeders (feed on the bottom of
water column) and are more susceptible than other fish to sediment
contamination. They also face greater exposure to urban and
agricultural runoff which tends to be concentrated in shoals where
splittail reside (Moyle et al. 2004, p. 23).
Laboratory studies have shown certain contaminants to potentially
have adverse effects on individual splittail. Field studies have shown
that the contaminants of concern are elevated in the Delta and co-occur
in areas important for splittail conservation. Although negative
impacts to individual splittail from contaminants are suspected and
have been shown on a limited basis, the overall extent of these impacts
to the population remains largely unknown without further study and
investigation. No information to date has conclusively shown that each
of the contaminants identified above have a significant effect on
splittail at the population level. In addition, several efforts are
being undertaken to improve estuarine habitat and reduce the amount of
contaminants discharged into the system. Therefore, we do not consider
the contaminants of concern, as described above, to constitute an
immediate threat to the species at this time or in the foreseeable
future.
Climate Change
The Intergovernmental Panel on Climate Change (IPCC) has concluded
that warming of the climate is unequivocal (2007, p. 5), and that
temperature increase is widespread over the globe and is greater at
northern latitudes (Soloman et al. 2007, p. 37). However, future
changes in temperature and precipitation will vary regionally and
locally, with some areas remaining unaffected or even decreasing in
temperature.
Between 1995 and 2006, 11 of the 12 years have been the warmest on
record (Soloman et al. 2007, p. 36). Over the next 20 years, climate
models estimate that the Earth's average surface temperature will
increase about 1.4 [deg]C (0.8 [deg]F). During the past decade, the
average temperature in California, like that of much of the globe, was
higher than observed during any comparable period of the past century
(Soloman et al. 2007, pp. 31-32). Nighttime air temperatures in
California have increased 0.18 [deg]C (0.33 [deg]F) per decade since
1920 while daytime temperatures have increased 0.05 [deg]C (0.1 [deg]F)
per decade since 1920 (CEC 2009, p. 10).
By IPCC estimates for 2070-2099, California temperatures are
expected to rise 1.6 to 2.7 [deg]C (3.0 to 5.5 [deg]F) under a low
emissions scenario and 4.4 to 5.8 [deg]C (8.0 to 10.5[deg]F) under a
high emissions scenario. However, recent studies have revealed that
emissions are rising faster than even the most aggressive high emission
scenarios used by IPCC in these calculations (CEC 2009 p. 41). Thus
temperatures in the State are expected to rise faster than predicted
unless global actions are taken to reduce emissions (CEC 2009 p. 41).
Similar to other California cyprinids, the splittail exhibits a
high thermal tolerance. Acclimated fish can survive temperatures up to
33 [deg]C (91.4 [deg]F) for short periods of time (Young and Cech 1996,
p. 670). Temperatures resulting from climate change in the next 50
years are not expected to stress splittail beyond their temperature
range. Splittail have historically adapted to changes in the Delta
system through
[[Page 62087]]
migratory behavior and it is likely that they will continue to adapt
and adjust their spawning and rearing grounds to areas with optimal
temperature conditions (Moyle et al. 2004, p. 38).
Changes in precipitation are less certain than temperature; climate
models project more frequent heavy precipitation events, separated by
longer dry spells, especially in the western United States (IPCC 2007,
p. 15). In California, snowfall in higher elevations has been
increasing while snowfall in lower elevations has been decreasing
(CEC2009, p. 16). This has led to an overall decrease in run-off of 19
percent in the San Joaquin Basin and 23 percent in the Sacramento Basin
between the months of April to July over the last 100 years, meaning
more runoff is coming in earlier months (CEC 2009, p. 17). Overall,
California snowpack is predicted to decrease by 20 to 40 percent by the
end of the century (CEC 2009, p. 44). However, due to the unpredictable
nature of climate change, we are uncertain how the amount of run-off
may vary over time and therefore we have no scientific evidence that
potential drought conditions resulting from climate change pose a
threat to the splittail.
Global sea level has risen at an average rate of 1.8mm (.07 inches)
per year from 1961 to 2003, and an average rate of 3.1 mm (.12 in) year
from 1993 to 2003 (IPCC 2007, p. 49). In California, sea level has
risen about 18 cm (7 in) in the last century (CEC 2009, p. 24), which
is similar to global sea level rise. The 2007 IPCC report modestly
estimates that sea levels could rise by 0.18 to .58 m (0.6 to 1.9 feet)
by 2100, but Rahmstorf (2007, p. 369) suggests that depending on the
warming scenario employed, global sea level rise could increase by over
1.2 m (4 ft) in that time period (CEC 2009, p. 49). Even if emissions
were halted today, oceans would continue to rise and expand for
centuries because of their efficient heat storing abilities (CEC 2009,
pp. 49-50). Current estimates put sea level rise at 20 to 50 cm (8 to
19 in) by 2050, which is likely to contribute to the flooding of at
least some Delta islands (Knowles 2010, pers. comm.).
The San Francisco estuary will be more susceptible to sea-level
rise due to its narrow bays and channels and because it already lies
below or at sea level (Moyle et al. 2004, p. 38). Many of the Delta
islands used for agriculture have been drained and armored with levees
for flood protection and groundwater level maintenance. These
reclamation and agricultural activities have caused island surface
levels to subside due to rapid decomposition of their water logged peat
soils. Many of the central and western Delta islands have experienced
the most subsidence, now lying at 3 to 7.6 m (10 to 25 ft) below sea
level (Ingebritsen et al. 2000, p. 2). These islands are at a high
level risk from sea level rise because, as islands subside and water
levels rise, levee banks are experiencing greater hydrostatic force,
thereby increasing the risk of their failure.
Earthquake fault models also show a high degree of risk of a
significant seismic event that could affect the islands in the central
and western Delta (Mount et al. 2005, p. 13). Failure of the levees on
some or all of these islands, as a result of liquefaction of the
unstable soils that make up the levees' foundations during an
earthquake, could turn part or the entire Delta into a brackish bay in
the future. The encroaching ocean would increase salinity levels in the
central and western Delta, with the result that the range of splittail
would likely be curtailed to some location upstream of the confluence
of the Sacramento and San Joaquin rivers.
Due to the divergence of two splittail population segments, one
population is exposed to higher salinities in the Napa and Petaluma
river systems for at least part of its life cycle (Feyrer et al. 2010,
p. 12). This population may be better able to adapt to increased
salinity levels that sea level rise may bring. Splittail have an
unusually high salinity tolerance and populations have shown great
resilience in waters with variable salinities (Moyle et al. 2004, p.
38; Young and Chech 1996, p. 673). Abundance indices soared in 1995 and
1998, in response to wet hydrological years following a decade of
predominantly dry conditions, showing the resilience of this species.
One problem climate change may pose to splittail is the reduced
spawning habitat due to deeper water (Moyle et al. 2007, p. 38).
However, new spawning habitat that may be created as a result of
flooding will help to accommodate splittail spawning in the event of
rising ocean levels. Liberty Island (discussed under Factor A) is one
example of the benefits that island flooding could have on splittail if
correctly managed. Under predicted future flooding conditions,
splittail could spawn in the Sutter Bypass and rear in the Delta.
Splittail have adapted to changes in the ecosystem through their
migratory behavior (Moyle 2004, p. 38) and may continue to do so in the
future.
Introduced Species
Copepods (E. affinis, Pseudodiaptomus forbesi), a major prey item
for splittail, have declined in abundance in the Delta since the 1970s
(Kimmerer and Orsi 1996, p. 409). Starting in about 1987, declines were
observed in the abundance of phytoplankton (Alpine and Cloern 1992, p.
951). These declines have been partially attributed to grazing by the
overbite clam (Corbula amurensis) (Kimmerer et al. 1994, p. 86) which
became abundant in the Delta in the late 1980s. Asiatic clams
(Corbicula fluminea) can exceed 200,000 per square meter (m2) and
overbite clam abundance can exceed 10,000 per m2 (Kimmerer et al. 2008,
p. 82). Because the overbite clam consumes copepod larvae as it feeds,
it not only reduces phytoplankton biomass but also competes directly
with splittail for food (Kimmerer et al. 1994, p. 87). It is believed
that these changes in the estuarine food web negatively influence
pelagic fish abundance, including splittail abundance. In the Delta,
phytoplankton production has declined 43 percent between 1975 and 1995
(Jasby et al. 2002, p. 703). The correlation of phytoplankton decline
with the appearance of the overbite clam leads us to believe that the
overbite clam is overgrazing the system.
Three non-native species of copepods (Sinocalanus doerrii,
Pseudodiaptomus forbesi, and Pseudodiaptomus marinus) became
established in the Delta between 1978 and 1987 (Carlton et al. 1990,
pp. 81-94), while native Eurytemora affinis populations have declined
since 1980. It is not known whether these non-native species have
displaced E. affinis or whether changes in the estuarine ecosystem now
favor S. doerrii and the two Pseudodiaptomus species. Meng and Orsi
(1991) reported that S. doerrii is more difficult for larval striped
bass to catch than native copepods because S. doerrii is fast swimming
and has an effective escape response. It is not known whether this
difference in copepod swimming and escape behavior has affected the
feeding success of young splittail.
Limnoithona tetraspina (no common name) is a nonnative copepod that
began increasing in numbers in the delta in the mid 1990s, about the
same time that P. forbesi began declining (Bennett et al. 2005, p. 18).
L. tetraspina is now the most abundant copepod species in the low
salinity zone (Bouley and Kimmerer 2006, p. 219), and is likely an
inferior prey species for splittail because of its smaller size and
superior predator avoidance abilities when compared to P. forbesi
(Bennett et al. 2005, p. 18; Baxter et al. 2008, p. 22).
Splittail have shifted their diet to utilize non-native species.
Although the
[[Page 62088]]
non-native copepods and bivalves discussed above have altered the food
web in the Delta ecosystem, we have no compelling evidence to suggest
that this has led to a decline in the splittail population. Please
refer to the bioaccumulation section for a full analysis of the effects
on splittail due to a shift in prey base from native species to the
overbite clam.
Chinese mitten crabs (Eriocheir sinensis) could reach
concentrations sufficient to intermittently impede the operation of
fish screens and salvage facilities, thus reducing the effectiveness of
splittail salvage and repatriation efforts. The US Bureau of
Reclamation has installed a device, known as ``Crabzilla'' to remove
Chinese mitten crab from their CVP fish salvage facility. However,
Chinese mitten crabs have not appeared in large numbers at either of
the fish salvage facilities in recent years. As a result of the
apparent decline of this nonnative species subsequent to their initial
appearance in the Delta, along with the measures taken at the CVP fish
salvage facility, the existence of the Chinese mitten crab in the Delta
is not a current threat to splittail.
Of some concern is the presence of Brazilian pondweed (Egeria
densa) and water hyacinth (Eichhornia crassipes), both of which tend to
form dense near-shore and slough-wide mats of vegetation that serve as
retreat, foraging, and ambush sites for splittail predators. These
vegetation mats also may divert upstream- and downstream-migrating
splittail into channels rather than the more-productive bankside
habitat by creating an obstacle (Moyle et al. 2004, p. 29).
Summary of Factor E
In summary, splittail are not significantly threatened by water
export facilities, agricultural and power plant diversions, poor water
quality, environmental contaminants, climate change, or introduced
species.
Operation of the CVP and SWP water export facilities directly
affects fish by entrainment into their diversion facilities. CVP and
SWP dams and diversions changed the historical hydrological features of
the watershed systems, have altered and eliminated habitat for
splittail, and may have reduced the distribution of the splittail by
restricting movement to potential spawning grounds and creating
migration obstacles. Entrainment at SWP and CVP pumps has not been
demonstrated to affect splittail at the population level because loss
of substantial numbers of fish tends to occur during wet years in which
the species is experiencing a high reproductive output. CALFED's
Ecosystem Restoration Program (discussed under Factors A and E, above)
has been successful in restoring habitat for the splittail and reducing
threats from entrainment at water diversion sites.
Splittail can become entrained in agricultural water diversions
resulting in injury or mortality. Under both the CALFED Bay-Delta
Program and the Central Valley Project Improvement Act, there have been
significant efforts to screen agricultural diversions in the Central
Valley and the Sacramento-San Joaquin Delta, and studies have found
splittail entrainment to be exceptionally low. We do not consider
entrainment by agricultural diversions to be a significant threat to
splittail.
Two power plants located near the confluence of the Sacramento and
San Joaquin rivers pose an entrainment risk to splittail. The intakes
for the cooling water pumps of these power plants are located in close
proximity to splittail rearing habitat (Moyle et al. 2004, p. 20).
Thermal and chemical pollution may also have a detrimental effect on
splittail (USFWS 2008, pp. 173-174). However, due largely to the
reduction in the operation of the power plants and their associated
pumping for cool water, we do not consider the operation of these power
plants to constitute a significant threat to the splittail population.
We have no indications of future plans to use these pumps more
frequently and therefore do not consider these operations to be a
threat in the future.
Laboratory studies have shown certain contaminants to be
detrimental to individual splittail and the co-occurrence of splittail
with contaminants has been documented. Although negative impacts to
individual splittail from contaminants have been shown, the overall
extent of such cases, and impacts to the population as a whole, remain
largely undocumented. No studies to date have shown contaminants to
have a significant effect on splittail at the population level.
Bioaccumulation of selenium and mercury in the overbite clam is
occurring and the overbite clam is a substantial prey item for
splittail. However, we have no evidence that the bioaccumulation of
selenium or mercury is having a detrimental effect on splittail at the
population level or will in the foreseeable future.
Climate change in California is expected to bring increased
temperatures, changes in precipitation and run-off, and increased
salinity levels associated with sea level rise. These changes may
restrict splittail range or reduce spawning habitat. However, splittail
exhibit high thermal salinity tolerances and are known to adapt to
changes in the Delta through migratory behavior. In addition, new
spawning habitat may be created as a result of flooding. We have no
scientific evidence that potential drought conditions resulting from
climate change pose a threat to the splittail.
Introduced species are having an effect on the food web and ecology
of the Estuary. Bivalves such as the overbite clam have displaced
native food sources of the splittail. However, splittail have shifted
their diets to utilize non-native food sources. Although the non-native
copepods and bivalves discussed above have altered the food web in the
Delta ecosystem, we have no compelling evidence to suggest that this
has led to a decline in the splittail population.
We conclude that the best scientific and commercial information
available indicates that the Sacramento splittail is not now, or in the
foreseeable future, threatened by other natural or manmade factors
affecting its continued existence.
Finding
As required by the Act, we considered the five factors in assessing
whether the Sacramento splittail is endangered or threatened throughout
all or a significant portion of its range. We have carefully examined
the best scientific and commercial information available regarding the
past, present, and future threats faced by the Sacramento splittail. We
reviewed the petition information available in our files, reviewed
other available published and unpublished information, and consulted
with recognized Sacramento splittail experts and other Federal, State,
and tribal agencies, including the California Department of Fish and
Game and the U.S. Bureau of Reclamation.
We identified and evaluated the risks of the present or threatened
destruction, modification, or curtailment of the habitat or range of
the Sacramento splittail. The rate of habitat loss in the Estuary that
occurred the 1900's is no longer occurring today and efforts undertaken
in the past decade have benefited the species by restoring its habitat.
There is presently sufficient habitat to maintain the species;
inundation frequency and duration in key areas is sufficient to provide
spawning to maintain the species. The implementation and magnitude of
the CALFED, CVPIA (discussed under Factor D) and other habitat
restoration activities, which focus on the restoration of habitats that
directly and
[[Page 62089]]
indirectly benefit splittail are greater than any foreseeable future
habitat losses. The overall effect of habitat restoration activities is
also expected to continue to be beneficial for splittail into the
foreseeable future. Based on a review of the best scientific
information available, we find that the present or threatened
destruction, modification, or curtailment of Sacramento splittail
habitat or range (Factor A) is not a significant threat to the
splittail now or in the foreseeable future.
The new CDFG regulation enacted in March 2010 limiting take of
splittail to two individuals per day has eliminated any potential
threat that fisheries may have posed. There is no indication that the
current level of scientific take adversely affects the splittail
population, and there is no indication that the level of mortality will
increase in the future. Based on a review of the best scientific
information available, we find that overutilization for commercial,
recreational, scientific, or educational purposes (Factor B) is not a
significant threat to the Sacramento splittail. We found disease occurs
at low levels in the population, but does not constitute a significant
threat to the species (Factor C). Predation by striped bass appears to
be unchanged from past levels, is currently not a significant threat to
splittail populations, and is not expected to increase in the future.
Largemouth bass populations have increased in the Estuary in the past
three decades, but populations of largemouth bass in critical rearing
areas are low, therefore predation levels appear to be minor. Based on
a review of the best scientific information available, we find that
disease and predation (Factor C) are not significant threats to the
Sacramento splittail, now or in the foreseeable future.
Federal and State regulations provide protection for the splittail
and its habitat by limiting adverse effects from new projects,
restoring habitat and limiting contaminants discharged into the
Estuary. Based on a review of the best scientific information, we find
that a lack of regulatory mechanisms (Factor D) does not constitute a
significant threat to the Sacramento splittail population now or in the
foreseeable future.
Based on the best available science, we find that other natural or
manmade factors affecting the continued existence of the splittail (as
described under Factor E) have not been shown to be significant threats
to the splittail at this time. Furthermore, there is no evidence to
suggest that these factors will increase and become threats to the
splittail in the foreseeable future. Splittail are not threatened by
water export facilities, agricultural and power plant diversions, poor
water quality, environmental contaminants, climate change, or
introduced species (Factor E). Entrainment at SWP and CVP pumps has not
been demonstrated to affect splittail at the population level. CALFED's
Ecosystem Restoration Program (discussed under Factors A and E above),
the CVPIA, and the provisions of the OCAP BOs, have been successful in
reducing threats from entrainment at water diversion sites. Under both
the CALFED Bay-Delta Program and the Central Valley Project Improvement
Act, there have been significant efforts to screen agricultural
diversions in the Central Valley and the Sacramento-San Joaquin Delta,
and studies have found splittail entrainment to be exceptionally low.
Therefore, we do not consider entrainment by agricultural diversions to
be a significant threat to splittail. Due to reduction in the operation
of two power plants and their associated pumping for cool water, we do
not consider the operation of these power plants to constitute a
significant threat to the splittail population. We have no indications
of future plans to use these pumps more frequently and therefore do not
consider these operations to be a threat in the future.
Laboratory studies have shown certain contaminants to be
detrimental to individual splittail and the co-occurrence of splittail
with contaminants has been documented. Although negative impacts to
individual splittail from contaminants have been shown, the overall
extent of such cases, and impacts to the population as a whole, remain
largely undocumented. No studies to date have shown contaminants to
have a significant effect on splittail at the population level.
Bioaccumulation of selenium and mercury in the overbite clam is
occurring and the overbite clam is a substantial prey item for
splittail. However, we have no evidence that the bioaccumulation of
selenium or mercury is having a detrimental effect on splittail at the
population level or will in the foreseeable future.
The existing data fails to show a significant long term decline of
the species. Natural fluctuations of population levels do not
constitute an overall decline in the species, but rather show a pattern
of successful spawning during wet years followed by reduced spawning
during dry years. The model deployed in this finding simulates the
species fluctuations and is compatible with known life history traits
of the species. Population levels are directly correlated with
inundation of floodplains and simulation models predict that these
habitats must flood at a minimum of every 7 years for the species to
persist in sufficient numbers to maintain a robust population level
(Moyle et al. 2004, p. 38). We have no evidence to show that the
frequency of inundation events on floodplains will decrease to the
point that these events will not be sufficient to maintain robust
population levels. Therefore, based on the best available data, we do
not find an overall declining trend in the species' population.
Although global warming will change hydrography in the Delta,
predictions do not foresee an imminent reduction in flooding of the
Yolo Bypass. Splittail have continually adapted to changes in the
ecosystem including salinity variation and we have no evidence to show
that this will not continue to be the case. The Yolo and Sutter
Bypasses and the Cosumnes River floodplain are serving as refuge for
the species and there is no evidence that these areas will not continue
to do so in the future. These floodplains are currently being expanded
through public and private partnerships including CALFED ERP, CVPIA,
Cosumnes River Preserve restoration efforts, and the acquisition and
restoration of Liberty Island.
Our review of the best available scientific and commercial
information pertaining to the five threat factors, does not support a
conclusion that there are independent or cumulative threats of
sufficient imminence, intensity, or magnitude to indicate that the
Sacramento splittail is in danger of extinction (endangered), or likely
to become endangered within the foreseeable future (threatened),
throughout its range. Therefore, listing the Sacramento splittail as
endangered or threatened is not warranted at this time.
Distinct Vertebrate Population Segments
After assessing whether the species is endangered or threatened
throughout its range, we next consider whether a distinct vertebrate
population segment (DPS) exists and meets the definition of endangered
or is likely to become endangered in the foreseeable future
(threatened).
Under the Service's DPS Policy Regarding the Recognition of
Distinct Vertebrate Population Segments Under the Endangered Species
Act (61 FR 4722; February 7, 1996), three elements are considered in
the decision concerning the establishment and classification of a
possible DPS. These are applied similarly for additions to or removal
from the Federal List of
[[Page 62090]]
Endangered and Threatened Wildlife. These elements include:
(1) The discreteness of a population in relation to the remainder
of the taxon to which it belongs;
(2) The significance of the population segment to the taxon to
which it belongs; and
(3) The population segment's conservation status in relation to the
Act's standards for listing, delisting, or reclassification (i.e., is
the population segment endangered or threatened).
In this analysis, we will evaluate whether the San Pablo population
of splittail is a DPS. This analysis is being conducted because recent
studies by Baerwald et al. (2007) have revealed genetic variation
between the San Pablo and Delta populations of splittail. The San Pablo
population of splittail represents a fraction of the overall splittail
population. For the purposes of this analysis, splittail individuals
that spawn in the Napa and Petaluma rivers will be referred to as the
San Pablo population and individuals that spawn in other rivers
including the Sacramento, San Joaquin and Cosumnes rivers will be
referred to as the Delta population.
Discreteness
Under the DPS policy, a population segment of a vertebrate taxon
may be considered discrete if it satisfies either one of the following
conditions:
(1) It is markedly separated from other populations of the same
taxon as a consequence of physical, physiological, ecological, or
behavioral factors. Quantitative measures of genetic or morphological
discontinuity may provide evidence of this separation.
(2) It is delimited by international governmental boundaries within
which differences in control of exploitation, management of habitat,
conservation status, or regulatory mechanisms exist that are
significant in light of section 4(a)(1)(D) of the Act.
The data used to determine genetic differences between two
splittail populations were collected in 2002 and 2003 and first
published in (Feyrer et al. 2005, pp. 164-167) to show upstream
distribution limits of splittail. Young of the year splittail
individuals were collected from the Napa, Petaluma, Cosumnes,
Sacramento and San Joaquin rivers and salinities were recorded at these
sites. Individuals collected from the farthest upstream locations on
the rivers were chosen for genetic analysis in an attempt to ensure
that they were collected in the natal rivers in which they were spawned
(Baerwald et al. 2007, p. 160).
Baerwald et al. (2007) used 13 microsatellite markers to
genetically distinguish 489 young-of-the-year splittail collected from
these five drainage areas (2007, pp. 160-161). Two genetically distinct
populations were found, one in the Napa/Petaluma (San Pablo population)
drainages and one in the greater Central Valley drainages (Delta
population) (Baerwald et al. 2007, p 162). Microsatellite markers are
neutrally inherited. Neutrally inherited genes come from the mother and
are always passed on to the next mother, where as the fathers genes may
or may not be passed on. The most likely reason for finding a
statistical difference in gene frequencies is isolation of spawning
populations (Israel and Baerwarld et al., 2010, pers. comm.). Both
splittail populations use Suisun Bay as rearing habitat in the
nonspawning season; however Suisun Marsh was used as foraging ground
almost exclusively by the Delta population (Baerwald et al. 2008, p.
1341). The majority (88 percent) of individuals collected foraging in
Suisun Marsh assigned to the Delta population; however, less
association was seen in individuals in the Ryer and Chipps Islands with
54 to 74 percent assigning to the Delta population (Baerwald et al.
2008, p. 1341). Although some overlap in foraging grounds was observed,
these populations largely maintain themselves in different habitats and
possess different genetic make-ups.
Thus, these studies demonstrate that the San Pablo population
segment, composed of individuals from the Napa and Petaluma rivers, is
markedly separate from the Delta population segment composed of
individuals from the Sutter Bypass and Sacramento, Cosumnes and San
Joaquin rivers as a consequence of genetic variation (Baerwald et al.
2007, pp. 164-165). Baerwald et al. noted that their results appear to
be correlated with differences in salinities between spawning grounds
and migration routes. Our analysis of the peer reviewed work done by
Baerwald et al. (2007 and 2008) leads us to conclude that the San Pablo
population is discrete under the Service's DPS policy.
Significance
If a population segment is considered discrete under one or more of
the conditions described in the Service's DPS policy, its biological
and ecological significance will be considered in light of
Congressional guidance that the authority to list DPSes be used
``sparingly'' while encouraging the conservation of genetic diversity.
In making this determination, we consider available scientific evidence
of the discrete population segment's importance to the taxon to which
it belongs. Since precise circumstances are likely to vary considerably
from case to case, the DPS policy does not describe all the classes of
information that might be used in determining the biological and
ecological importance of a discrete population. However, the DPS policy
describes four possible classes of information that provide evidence of
a population segment's biological and ecological importance to the
taxon to which it belongs. As specified in the DPS policy (61 FR 4722),
this consideration of the population segment's significance may
include, but is not limited to, the following:
(1) Persistence of the discrete population segment in an ecological
setting unusual or unique to the taxon;
(2) Evidence that loss of the discrete population segment would
result in a significant gap in the range of a taxon;
(3) Evidence that the discrete population segment represents the
only surviving natural occurrence of a taxon that may be more abundant
elsewhere as an introduced population outside its historic range; or
(4) Evidence that the discrete population segment differs markedly
from other populations of the species in its genetic characteristics.
A population segment needs to satisfy only one of these conditions
to be considered significant. Furthermore, other information may be
used as appropriate to provide evidence for significance.
(1) Persistence of the discrete population segment in an ecological
setting unusual or unique to the taxon.
Salinity concentrations were recorded between April and July in
2002 and 2003 on the Sacramento, San Joaquin, Napa, and Petaluma rivers
at various locations where splittail were collected. Salinity
concentrations on the Petaluma River averaged 13.0 ppt in 2002 and 6.0
ppt in 2003. Napa River salinity concentrations averaged 5.0 ppt in
2002 and 0.0 ppt in 2003. The San Joaquin and Sacramento rivers
averaged 0.0 ppt for both years (Baerwald et al. 2008, p. 165).
Sacramento and San Joaquin rivers never contained salinity
concentrations higher than 1.0 ppt. Salinity concentrations on the Napa
River ranged between 0.0-8.5 ppt while Petaluma River salinity
concentrations ranged between 5.5-14.1 ppt (Feyrer et al. 2010, p. 8).
It is speculated that high salinities are creating a barrier between
these populations that is only broken during high outflow years (Feyrer
et al. 2010, p. 11). This barrier likely occurs
[[Page 62091]]
in the area of Carquinez Straight between Suisun Bay and San Pablo Bay.
Napa River populations mostly associate with the San Pablo
population although a small number of individuals caught in 2003 when
the salinity was 0.0 ppt on the Napa River associated with the Delta
population. The presence of the Delta population in the Napa River in
2003, when the salinity was 0.0 ppt and absence in 2002 when salinities
were higher may reflect the Delta population's limited ability to
tolerate high salinities for spawning.
The data we have clearly shows that the Napa and Petaluma rivers
had higher salinities than other areas of the Delta where the splittail
persists for the 2 years that surveys were conducted. However, we feel
that 2 years of data are not sufficient to conclude that this
constitutes a unique ecological setting that is persistent over time. A
larger data set covering more years is needed to assess the salinities
of these rivers particularly at splittail spawning grounds before we
can conclude the range of the San Pablo population constitutes a unique
ecological environment. Therefore, we are lacking convincing evidence
that shows the San Pablo population persists in an unusual or unique
ecological setting that contributes significantly to the taxon at this
time.
(2) Evidence that loss of the discrete population segment would result
in a significant gap in the range of a taxon;
The San Pablo population segment is on the western edge of the
species range and only constitutes a small portion of the species
range. Loss of this population would not create a gap in the remainder
of the species range because the San Pablo population does not provide
for connectivity with other portions of the range. Therefore, we
conclude that loss of this population would not represent a significant
gap in the range of the species.
(3) Evidence that the discrete population segment represents the only
surviving natural occurrence of a taxon that may be more abundant
elsewhere as an introduced population outside its historic range.
This criterion does not apply to the San Pablo splittail population
because it is not a population segment representing the only surviving
natural occurrence of the taxon that may be more abundant elsewhere as
an introduced population outside its historical range.
(4) Evidence that the discrete population segment differs markedly from
other populations of the species in its genetic characteristics.
Under the DPS policy we measure the evidence for potential
biological and ecological significance to the species as a whole, as
reflected by marked differences in its genetic characteristics.
Evidence that the discrete population segment differs markedly from
other populations of the species in its genetic characteristics is
provided in the Baerwald et al study. (2007, p. 166). These genetically
distinct populations may be driven by the strong selective pressure
separating out species that are salinity tolerant from those that are
susceptible to salinity effects (Baerwald et al. 2007, p. 165). We
conclude that the San Pablo population of splittail meets this
criterion of the DPS policy because it differs markedly from other
populations in its genetic characteristics.
Determination of Distinct Population Segment
Based on the best scientific and commercial information available,
as described above, we find that under the Service's DPS policy, the
San Pablo population segment is discrete and is significant to the
taxon to which it belongs. Evidence that the San Pablo splittail is
biologically and ecologically significant from other populations of
splittail is based on the evidence that the discrete population segment
differs markedly from other populations of the species in its genetic
characteristics. Because the San Pablo population segment is both
discrete and significant, it qualifies as a DPS under the Act.
Distinct Population Segment Five-Factor Analysis
Since the San Pablo population segment qualifies as a DPS, we will
now evaluate its status with regard to its potential for listing as
endangered or threatened under the five factors listed in section 4(a)
of the Act. The majority of the factors affecting the species
throughout its range also affect the San Pablo DPS of splittail. These
factors can be found in the five factor analysis conducted for the
entire range of the splittail found above. Our evaluation of the San
Pablo DPS follows.
Factor A. The present or threatened destruction, modification, or
curtailment of its habitat or range
Habitat Loss
Rapid development within the San Pablo DPS' range began with the
discovery of gold in the Sierra Nevada foothills in the 1850s.
Hydraulic mining operations contributed huge amounts of sediment to San
Pablo Bay. For the next hundred years, the marshes were filled, diked,
or drained to support the bay's development as a major center of
commerce. About 85 percent of the historic tidal marshes of San Pablo
Bay have been altered, negatively affecting the ability of the
remaining tidal marshes to accept winter rainfall and purify water in
the bay.
Beneficial Actions Offsetting Adverse Effects
Since the 1960s, State and government agencies, non-profit
organizations, and local grassroots organizations have made efforts to
protect and restore San Pablo Bay. The San Pablo Bay National Wildlife
Refuge was established in 1974 and currently protects over 13, 000
acres of wildlife habitat. Largely comprised of thousands of acres of
tidelands leased from the California State Lands Commission, the
refuge's ultimate plans include protection and conservation of more
than 8,094 ha (20,000 ac) of critical wildlife in northern San Pablo
Bay (FWS Brochure 2001, pp. 1-6). Additional efforts are underway to
protect and restore the bay. The San Pablo Bay Preservation Society is
currently working to acquire land on San Pablo point (http://
www.pointsanpablo.org/) and the friends of San Pablo Bay NWR have
helped to establish a nursery that is being used to re-vegetate tidal
wetlands.
Although the historic loss of floodplains has detrimentally
affected the species in the past, current laws and protections
including the creation of the San Pablo Bay National Wildlife Refuge
have largely eliminated future losses of floodplain to the splittail.
Many of the natural floodplains in the Napa and Petaluma rivers are
still intact and provide optimal spawning grounds to splittail. The San
Pablo DPS is much closer to the ocean than the Delta DPS and is largely
influenced by a tidal system. Fresh water input into the system is
essential to provide proper salinity levels. Over the past 100 years,
fresh water input has been reduced by diversions and water barriers.
Although, this reduction in fresh water flow has changed salinity
concentrations in the Napa and Petaluma rivers, we have no evidence to
suggest that it has had a significant effect on the population level of
the species.
Recent Abundance Data Trends
On June 1, 2010, splittail individuals encompassing both young-of-
the-year (less than 1 year in age) and age one
[[Page 62092]]
were captured in the Petaluma River (Sommer et al. unpublished, pp. 1-
3). The presence of splittail from two different age classes makes it
likely that splittail successfully spawned in the Petaluma River in
2010 (a relatively wet year) and 2009 (a critically dry year). This
shows that splittail are persisting in the Petaluma River. In addition,
all 10 of the fish captured in the survey belonged to the San Pablo
population of splittail. During this survey, fish were collected at two
out of three survey sites. During previous surveys in the Petaluma
River, splittail were captured at one out of three sites (Feyrer et al.
2005, p. 162).
We have no evidence at this time to suggest that the San Pablo
population of splittail is in decline. The accepted range of the
species in the Napa and Petaluma rivers has increased as new surveys
have found presence of splittail in areas where they were previously
not believed to be in the mid-1990's (Sommer et al. 2007, p. 28).
Summary of Factor A
Although there has been substantial loss of habitat historically,
present and future loss of habitat is expected to be minimal due to
current land protections including the San Pablo Bay National Wildlife
Refuge. Efforts undertaken in the past decade have benefited the
species by restoring its habitat. There is presently sufficient habitat
to maintain the species, inundation frequency and duration in key areas
is sufficient to provide spawning to maintain the species. We conclude
that the best scientific and commercial information available indicates
that the San Pablo DPS of Sacramento splittail is not now, or in the
foreseeable future, threatened by the present or threatened
destruction, modification, or curtailment of its habitat or range.
Factor B. Overutilization for commercial, recreational, scientific, or
educational purposes
Recreational Fishing
Take of splittail due to fisheries is a potential threat rangewide
to the species and this threat is not expected to be any different for
the San Pablo DPS. Please refer to Factor B in the rangewide analysis
for a full discussion of take due to recreational fishing. Take due to
recreational fishing is not considered to be a substantial threat to
the San Pablo DPS of splittail at this time.
Scientific Collection
Take and fatalities attributed to scientific sampling in areas
occupied by the San Pablo population of splittail are far less than the
rangewide take of the species. There have only been 10 known surveys of
the San Pablo DPS splittail in the last 10 years. These include five
U.S. Army Corp of Engineers' surveys (2001 and 2002), three surveys
conducted by Feyrer et al.(2002, 2003 and 2010) and one study by the
Napa Creek Floodplain Project (2007). There were a total of 4 splittail
captured in 2001 (USACE 2002), 79 captured in 2002 (USACE 2002), 48
captured in 2003 (USACE 2004), 326 captured in 2004 (USACE 2004), and
305 captured in 2005 (USACE 2006) by the Army Core of Engineers. None
of the fish captured by the Corps were kept. The amounts of Yyung-of-
the-year captured in the Feyrer et al. studies were: 112 in the Napa
River and 45 in the Petaluma River in 2002, and 62 in the Napa River
and 171 in the Petaluma River in 2003 (Feyrer 2010, pers. comm.).
During a short gill net study in 2003, Feyrer et. al. collected 108
adult splittail (Feyrer 2010, pers. comm.). A total of 13 splittail
were captured in 2010. All of the splittail taken in the Feyrer et al.
studies were preserved for genetic analyisis. There were seven
splittail caught in the Napa Creek Floodplain Project study in June of
2007 (Turner 2007). Female splittail can lay up to 100, 000 eggs in a
single spawning event and the take of several hundred individuals is
not expected to effect the population at the species level. Therefore,
scientific take is not considered to be a significant threat to
splittail at this time, however, scientific studies regarding the San
Pablo population of splittail have been kept to a minimum to be sure
not to threaten the limited number of individuals present in this
population (Feyrer et al. 2010, pers. comm.)
Summary of Factor B
The new CDFG regulation enacted in March 2010 limiting take of
splittail to two individuals per day has eliminated any potential
threat that fisheries may have posed. There is no indication that the
current level of scientific take adversely affects the splittail
population, and there is no indication that the level of mortality will
increase in the future. We conclude that the best scientific and
commercial information available indicates that the San Pablo DPS of
the Sacramento splittail is not now, or in the foreseeable future,
threatened by overutilization for commercial, recreational, scientific
or educational purposes.
Factor C. Disease or predation
Disease
Disease is a potential threat to splittail rangewide including in
the San Pablo Bay and the potential threat of disease is expected to be
the same in scope and intensity as it is in the overall range of the
population. Please refer to Factor C in the range wide analysis for a
full discussion of the effects of disease on splittail. Based on a
review of the best scientific information available, we find that
disease is not a significant threat to the San Pablo Bay population of
splittail now or in the foreseeable future.
Predation
The salinity level in San Pablo Bay and the Napa and Petaluma
rivers serves as a barrier to potential predators of the San Pablo DPS
of splittail. Predators such as largemouth bass and catfish are not
able to tolerate the high salinity environment present in the area of
the San Pablo Bay population. The only substantial predator of
splittail that is able to reside in this environment is the striped
bass (Nobriga 2010, pers. comm.).
Based on a review of the best scientific information available, we
find that predation is not a significant threat to the San Pablo Bay
population of splittail now or in the foreseeable future.
Summary of Factor C
We found disease occurs at low levels in the population, but does
not constitute a significant threat to the species. Because the
potential threat of predation on the San Pablo DPS of splittail is
expected to be less than the potential threat on the overall population
due to a salinity barrier, we conclude that predation is not a
significant threat to the San Pablo population now or in the
foreseeable future. We conclude that the best scientific and commercial
information available indicates that the San Pablo Bay DPS of the
Sacramento splittail is not now, or in the foreseeable future,
threatened by disease or predation.
Factor D. The inadequacy of existing regulatory mechanisms
State Laws
State laws acting as existing regulatory mechanisms are expected to
provide the same protections to the San Pablo Bay DPS of splittail as
they do to the entire range of the species because the laws are uniform
throughout the State of California. Please refer to Factor D in the
rangewide analysis for a full discussion of the State laws acting as
[[Page 62093]]
existing regulatory mechanisms to provide protections to the splittail.
Federal Laws
Federal laws acting as existing regulatory mechanisms are expected
to provide the same protections to the San Pablo Bay DPS of splittail
as they do to the entire range of the species because the laws are
uniform throughout the United States. Please refer to Factor D in the
rangewide analysis for a full discussion of the Federal laws acting as
existing regulatory mechanisms to provide protections to the splittail.
Summary of Factor D
Federal and State regulations described in the analysis of the
entire species range provide protection for the splittail and its
habitat by limiting adverse affects from new projects, restoring
habitat and limiting contaminants discharged into the Estuary. Although
the Act does not directly regulate actions in splittail habitat, the
provisions in the Act that apply to other listed species benefit the
splittail. We conclude that the best scientific and commercial
information available indicates that the San Pablo DPS of the
Sacramento splittail is not now, nor in the foreseeable future,
threatened by inadequate regulatory mechanisms.
Factor E. Other natural or manmade factors affecting its continued
existence
We have identified the risk of water export facilities,
agricultural and power plant diversions, poor water quality,
environmental contaminants, climate change, or introduced species as
potential threats to the San Pablo DPS of splittail.
Water export facilities
Water export facilities (CVP and SWP pumps) and power plant
diversions which were analyzed in the range wide splittail finding are
not located within the range of the San Pablo DPS and therefore do not
represent potential threats to the San Pablo DPS. Water export
facilities do not exist in the area of the San Pablo DPs and therefore
are not considered to be a substantial threat to splittail now or in
the foreseeable future.
Agricultural Diversions for Irrigation
Agricultural diversions are a potential threat range wide to
splittail including in the area occupied by the San Pablo DPS. The
majority of agricultural diversions in the Napa River are utilized by
wineries for the production of grapes. Wine production in the Napa
Valley is a multimillion dollar industry. There are a total of 1200
agricultural diversions in Napa County. Of these, there are 99 active
diversions in the Napa River itself and they are primarily attributed
to wine production (California integrated water quality systems 2010,
p. 1). Splittail populations are persisting in the Napa and Petaluma
Rivers and we have no data to show that agricultural diversions are a
significant threat to the continued existence of the species at the
population level now or in the foreseeable future.
Power Plant Diversions
There are no power plant diversions within the range of the San
Pablo DPS of splittail. The Contra Costa Power Plant and the Pittsburg
Power Plant (discussed in the rangewide analysis) are not a factor
because they are located outside of the range of the San Pablo DPS of
splittail. Power plant diversions are not expected to be a threat to
the San Pablo population of splittail now or in the foreseeable future.
Water Quality and Environmental Contaminants
The Napa River exhibits a high eutrophication rate and has been
placed on California List of Impaired Water Bodies (303(d) list)
because nutrients, pathogens and sedimentation. The Petaluma River is
on the California List of Impaired Water Bodies (303(d) list) for
possessing high elevations of diazinon, nutrients, and sedimentation.
The primary symptom of excessive nutrient loading in this watershed is
dense algae growth. Eutrophication occurs when high nutrient levels
increase growth of plant and algal matter resulting in dissolved oxygen
removal from the system when the plants die and begin to decompose
(Wang et al. 2004, p. 10).
Efforts are underway by State water resource staff to address many
nutrient sources including faulty septic systems, agricultural and
urban runoff, and livestock through regulatory programs. These programs
will address multiple pollutants, including pathogens, nutrients, and
sediment. The Napa County resource conservation district has ongoing
restoration efforts including native plant re-vegetation, road
improvements, fish barrier removal, upland habitat improvements, and
stream and wetland restoration. A Napa sustainable winegrowing group is
active in educating wine growers on the benefits of reducing pesticide
use and promoting soil health through erosion control.
Although the Napa and Petaluma rivers do exhibit a high amount of
nutrients, we have no evidence at this time to suggest that nutrient
loading is causing a decline in the San Pablo DPS of splittail at the
population level now or that it will in the foreseeable future. The
known range of the species in the Napa and Petaluma rivers has
increased as new surveys have found presence of splittail in areas
where they were previously not believed to be found in the mid 1990's
(Sommer et al. 2007, p. 28).
Effects from selenium, mercury, organophosphates, pyrethroids and
bioaccumulation on the San Pablo DPS are expected to be comparable to
the effects that these potential threats are having on the overall
population of splittail. These contaminants are dispersed throughout
the estuary and we have no evidence to suggest that there is a higher
concentration of these contaminants in the range of the San Pablo DPS
than in the entire range of the species. Please refer to Factor E in
the range wide analysis for a full discussion of the effects of
contaminants on splittail. Based on a review of the best available
scientific and commercial data, we conclude that contaminants are not a
significant threat to splittail at the population level now or in the
foreseeable future.
Climate Change
Climate change is a potential threat to splittail range wide
including in the San Pablo Bay and the potential threat of climate
change is expected to be the same in scope and intensity as it is in
the overall range of the species. Please refer to Factor E in the range
wide analysis for a full discussion of the effects of climate change on
splittail. Based on a review of the best scientific information
available, we find that climate change is not a significant threat to
the San Pablo Bay population of splittail now or in the foreseeable
future.
Introduced Species
Introduced species are a potential threat to the splittail
rangewide and the effects of introduced species on the San Pablo DPS
are expected to be similar to the effects on the species range-wide.
However, several introduced species mentioned in the range-wide
analysis will not be present in the San Pablo Bay. The invasive Corbula
amurensis has become established in San Pablo Bay (USGS 2010); no
records exist for Corbicula fluminea, which is physiologically capable
of becoming established in the freshwater portions of the Petaluma and
Napa rivers. Corbicula fluminea is not expected to be present in the
San Pablo Bay because it is a
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freshwater clam. Largemouth bass are not expected to be present in San
Pablo Bay because they are a freshwater species.
Brazilian pondweed and water hyacinth are also not expected to be
present in this brackish environment because they are freshwater
plants. We are lacking any studies on introduced species present in the
Napa and Petaluma rivers. Although the non-native copepods and bivalves
discussed in the rangewide analysis have altered the food web in the
Delta ecosystem, we have no compelling evidence to suggest that this
has led to a decline in the splittail population. Therefore, we do not
consider introduced species to be a significant threat to splittail now
or in the foreseeable future.
We conclude that the best scientific and commercial information
available indicates that the San Pablo DPS of the Sacramento splittail
is not now, nor in the foreseeable future, threatened by other natural
or manmade factors affecting its continued existence.
Finding
As required by the Act, we considered the five factors in assessing
whether the San Pablo DPS of Sacramento splittail is endangered or
threatened. We examined the best scientific and commercial information
available regarding the past, present, and future threats faced by the
San Pablo DPS.
The rate of habitat loss in San Pablo Bay that occurred the 1900's
is no longer occurring today and efforts undertaken in the past decade
have benefited the species by restoring its habitat. There is presently
sufficient habitat to maintain the species: inundation frequency and
duration in key areas is sufficient to provide spawning to maintain the
species. Based on a review of the best scientific information
available, we find that the present or threatened destruction,
modification, or curtailment of splittail habitat or range (Factor A)
is not a significant threat to the San Pablo DPS throughout all or a
part of its range.
The new CDFG regulation enacted in March 2010 limiting take of
splittail to two individuals per day has eliminated any potential
threat that fisheries may have posed. There is no indication that the
current level of scientific take adversely affects the San Pablo DPS,
and there is no indication that the level of mortality will increase in
the future. Based on a review of the best scientific information
available, we find that overutilization for commercial, recreational,
scientific, or educational purposes (Factor B) is not a significant
threat to the San Pablo DPS now or in the foreseeable future.
We found disease occurs at low levels in the population, but does
not constitute a significant threat to the species (Factor C).
Predation by striped bass appears to be unchanged from past levels and
is currently not a significant threat to the San Pablo DPS. Other
freshwater predators are absent from the San Pablo Bay due to elevated
salinity levels. Based on a review of the best scientific information
available, we find that disease and predation (Factor C) are not
significant threats to the San Pablo DPS in all or a significant
portion of its range, now or in the foreseeable future.
Federal and State regulations provide protection for the San Pablo
DPS and its habitat by limiting adverse effects from new projects,
restoring habitat and limiting contaminants discharged into the
Estuary. Based on a review of the best scientific information, we find
that a lack of regulatory mechanisms (Factor D) does not constitute a
significant threat to the San Pablo DPS.
Based on the best available science, we find that other natural or
manmade factors affecting the continued existence of the San Pablo DPS
described in Factor E have not been shown to be significant threats to
the San Pablo DPS at this time. Furthermore, there is no compelling
evidence to suggest that these factors will increase and become threats
to the San Pablo DPS in the foreseeable future. The San Pablo DPS is
not threatened by water export facilities, agricultural and power plant
diversions, poor water quality, environmental contaminants, climate
change, or introduced species (Factor E).
The existing data fails to show a significant long-term decline of
the San Pablo DPS. The accepted range of the species in the Napa and
Petaluma rivers has increased as new surveys have found presence of
splittail in areas where they were previously not believed to be in the
mid-1990's (Sommer et al. 2007, p. 28).Therefore, based on the best
available data, we do not find an overall declining trend in the
species' population.
Based on our review of the best available scientific and commercial
information pertaining to the five factors, we find that the threats
are not of sufficient imminence, intensity, or magnitude to indicate
that the San Pablo DPS is in danger of extinction (endangered), or
likely to become endangered within the foreseeable future (threatened).
Therefore, we find that listing the San Pablo DPS as an endangered or
threatened species is not warranted at this time.
Significant Portion of the Range Analysis
Having determined that the splittail does not meet the definition
of an endangered or threatened species, we must next consider whether
there are any significant portions of the range where the splittail is
in danger of extinction or is likely to become endangered in the
foreseeable future.
We have analyzed the potential for the San Pablo DPS to make up a
significant portion of the species range by looking at areas where
there may be a significant concentration of threats. We evaluated the
San Pablo DPS in the context of whether any potential threats are
concentrated in one or more areas of the projected range, such that if
there were concentrated impacts, those splittail populations might be
threatened, and further, whether any such population or complex might
constitute a significant portion of the species range. In the case of
the San Pablo DPS, we conclude that the potential threats to the
species are uniform throughout the DPS. After reviewing the range of
the species, we find that no areas have a significant concentration of
threats such that a significant portion of the range analysis on them
would be necessary.
We do not find that the Sacramento splittail is in danger of
extinction now, or is it likely to become endangered within the
foreseeable future throughout all or a significant portion of its
range. Therefore, listing the Sacramento splittail as endangered or
threatened under the Act is not warranted at this time.
We request that you submit any new information concerning the
status of, or threats to, the Sacramento splittail or the markedly
separate San Pablo DPS to our San Francisco Bay Delta Fish and Wildlife
Office (see ADDRESSES) whenever it becomes available. New information
will help us monitor the Sacramento splittail and encourage its
conservation. If an emergency situation develops for the splittail or
any other species, we will act to provide immediate protection.
References Cited
A complete list of references cited in this finding is available on
the Internet at http://www.regulations.gov and upon request from the
San Francisco Bay Delta Fish and Wildlife Office (see ADDRESSES).
Author(s)
The primary authors of this notice are the staff members of the San
Francisco Bay Delta Fish and Wildlife Office, Sacramento, California.
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Authority
The authority for this section is section 4 of the Endangered
Species Act of 1973, as amended (16 U.S.C. 1531 et seq.).
Dated: September 24, 2010
Daniel M. Ashe,
Acting Director, Fish and Wildlife Service.
[FR Doc. 2010-24871 Filed 10-6-10; 8:45 am]
BILLING CODE 4310-55-S