2011 Federal Register, 76 FR 63444; Centralized Library: U.S. Fish and Wildlife Service - Federal Register, Volume 76 Issue 197 (Wednesday, October 12, 2011)

[Federal Register Volume 76, Number 197 (Wednesday, October 12, 2011)]
[Proposed Rules]
[Pages 63444-63478]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2011-25810]

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Vol. 76

Wednesday,

No. 197

October 12, 2011

Part IV

Department of the Interior

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Fish and Wildlife Service

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50 CFR Part 17

Endangered and Threatened Wildlife and Plants; 12-Month Finding on a
Petition To List Northern Leatherside Chub as Endangered or Threatened;
Proposed Rule

Federal Register / Vol. 76 , No. 197 / Wednesday, October 12, 2011 /
Proposed Rules

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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R6-ES-2011-0092; MO 92210-0-0008-B2]

Endangered and Threatened Wildlife and Plants; 12-Month Finding
on a Petition To List Northern Leatherside Chub 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 (Service), announce a
12-month finding on a petition to list the northern leatherside chub
(Lepidomeda copei) as endangered or threatened and to designate
critical habitat under the Endangered Species Act of 1973, as amended
(Act). After review of all available scientific and commercial
information, we find that listing the northern leatherside chub
rangewide is not warranted at this time. We ask the public to submit to
us any new information that becomes available concerning the threats to
the northern leatherside chub or its habitat at any time.

DATES: The finding announced in this document was made on October 12,
2011.

ADDRESSES: This finding is available on the Internet at http://www.regulations.gov at Docket Number FWS-R6-ES-2011-0092. 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, Utah Ecological Services Field Office, 2369
West Orton Circle, Suite 50, West Valley City, UT 84119. Please submit
any new information, materials, comments, or questions concerning this
finding to the above street address.

FOR FURTHER INFORMATION CONTACT: Larry Crist, Field Supervisor, Utah
Ecological Services Field Office (see ADDRESSES); by telephone at 801-
975-3330; or by facsimile at 801-975-3331; or Brian Kelly, Field
Supervisor, Idaho Ecological Services Field Office; by telephone at
208-378-5243; or by facsimile at 208-378-5262. 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 Act (16 U.S.C. 1531 et seq.) requires
that, for any petition to revise the Federal Lists of Endangered and
Threatened 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
endangered 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

On July 30, 2007, we received a petition dated July 24, 2007, from
Forest Guardians (now WildEarth Guardians), requesting that the
Service: (1) Consider all full species in our Mountain Prairie Region
ranked as G1 or G1G2 by the organization NatureServe, except those that
are currently listed, proposed for listing, or candidates for listing;
and (2) list each species as either endangered or threatened. The
petition included the northern leatherside chub (Lepidomeda copei),
which is addressed in this finding. The petition incorporated all
analysis, references, and documentation provided by NatureServe in its
online database at http://www.natureserve.org/into the petition. The
document clearly identified itself as a petition and included the
petitioners' identification information, as required in 50 CFR
424.14(a). We sent a letter to the petitioners, dated August 24, 2007,
acknowledging receipt of the petition and stating that, based on
preliminary review, we found no compelling evidence to support an
emergency listing for any of the species covered by the petition.
On March 19, 2008, WildEarth Guardians filed a complaint (1:08-CV-
472-CKK) indicating that the Service failed to comply with its
mandatory duty to make a preliminary 90-day finding on their two
multiple species petitions--one for mountain-prairie species, and one
for southwest species.
On February 5, 2009 (74 FR 6122), we published a 90-day finding on
165 species from the petition to list 206 species in the mountain-
prairie region of the United States as endangered or threatened under
the Act. We found that the petition did not present substantial
scientific or commercial information indicating that listing was
warranted for these species and, therefore, did not initiate further
status reviews in response to the petition. Two additional species were
reviewed in a January 6, 2009, 90-day finding (74 FR 419) and,
therefore, were not considered further in the February 5, 2009, 90-day
finding. For the remaining 39 species, we deferred our findings until a
later date. One species of the 39 remaining species, Sphaeralcea
gierischii (Gierisch mallow), was already a candidate species for
listing; therefore, 38 species remained. On March 13, 2009, the Service
and WildEarth Guardians filed a stipulated settlement in the District
of Columbia Court, agreeing that the Service would submit to the
Federal Register a 90-day finding on the remaining 38 mountain-prairie
species by August 9, 2009.
On August 18, 2009, we published a notice of 90-day finding (74 FR
41649) on 38 species from the petition to list 206 species in the
mountain-prairie region of the United States as endangered or
threatened under the Act. Of the 38 species, we found that the petition
presented substantial scientific and commercial information for 29
species indicating that a listing may be warranted. The northern
leatherside chub addressed in this 12-month finding was included in the
list of 29 species. We initiated a status review of the 29 species to
determine if listing was warranted. We also opened a 60-day public
comment period to allow all interested parties an opportunity to
provide information on the status of the 29 species. The public comment
period closed on October 19, 2009. We received 224 public comments. Of
these, five specifically mentioned northern leatherside chub. All
substantial information we received was carefully considered in this
finding. This notice constitutes the 12-month finding on the July 24,
2007, petition to list the northern leatherside chub as endangered or
threatened.

Species Information

The northern leatherside chub (Lepidomeda copei) is a rare desert
fish in the minnow family (Cyprinidae) that occurs in northern Utah and
Nevada, southern and eastern Idaho, and western

[[Page 63445]]

Wyoming (Johnson et al. 2004, pp. 842-843; Utah Division of Wildlife
Resources (UDWR) 2009, pp. 28-30; McAbee 2011, entire). The species is
native to smaller, mid-elevation, desert streams in the northeastern
portions of the Great Basin region (draining to the Great Salt Lake)
and the southern and eastern portions of the Pacific Northwest Region
(draining to the Pacific Ocean) (Johnson et al. 2004, pp. 842-843; UDWR
2009, pp. 28-30). Like many western North American non-game fish
species, little was known about its biology, ecology, or status until
recently (Belk and Johnson 2007, pp. 67-68).
Taxonomy and Species Description
The northern leatherside chub is one of two species, along with the
southern leatherside chub (Lepidomeda aliciae), recently re-classified
from the single species `leatherside chub' (Snyderichthys copei or Gila
copei) (Johnson et al. 2004, pp. 841, 852). Throughout the remainder of
this finding, references to leatherside chub indicate data collected
before the two species were delineated, and references to southern
leatherside chub and northern leatherside chub indicate data specific
to each species, exclusively. Because the northern and southern species
were only recently separated, most species descriptions and life-
history investigations are a combination of the two species. While many
characteristics are common to both species, we will describe
characteristics of only the northern leatherside chub when possible.
The taxonomic history of leatherside chub is complex. Even when
considered a single species, taxonomists classified the leatherside
chub in at least seven different genera over the past century and a
half (Johnson et al. 2004, p. 841). The type locality for leatherside
chub (Squalius copei; Jordan and Gilbert 1881) is from the Bear River
at Evanston, Wyoming (UDWR 2009, p. 24). Classification by Miller in
the mid-twentieth century (1945) placed leatherside chub in the
monotypic genus Snyderichthys, but shortly thereafter Uyeno (1960)
assigned it to the genus Gila (the chubs), subgenus Snyderichthys (UDWR
2009, p. 25). Many fisheries texts accepted Gila copei as the taxonomic
classification over the next 40 years (Sigler and Miller 1963, p. 74;
Sigler and Sigler 1996, p. 77), but acceptance was not unanimous, as
evidenced by the American Fisheries Society supporting Snyderichthys
copei in 2004 (UDWR 2009, p. 25). Taxonomic discrepancy was not fully
rectified until a short time ago. Recent research demonstrated that
what was previously considered the `leatherside chub' is in fact two
distinct species with discrete geographic, ecological, morphological,
and genetic characteristics (Johnson et al. 2004, pp. 841, 852).
Moreover, neither species belongs in the previously accepted genera,
but rather both belong in the genus Lepidomeda, a group commonly
referred to as the spinedaces (Johnson et al. 2004, pp. 841, 852).
Three different species concepts validate this taxonomic revision.
Genetic analysis endorses two evolutionarily separate species under the
phylogenetic species concept (defines a species as a set of organisms
with a unique genetic history) (Johnson and Jordan 2000, pp. 1029,
1033; Johnson et al. 2004, pp. 841, 851). In addition, morphologic
(cranial shape) and ecological (feeding and growth rates) divergence
support two distinct species under the similarity and ecological
species models, respectively (Johnson et al. 2004, p. 851). It also is
worth noting that current taxonomy aligns with discrete geographic
distributions of the species, with the unoccupied Weber River
separating the two species' ranges and the uninhabitable Great Salt
Lake preventing natural interaction between individuals of the two
species (Belk and Johnson 2007, p. 69). Supported by multiple lines of
evidence indicating that southern (Lepidomeda aliciae) and northern (L.
copei) leatherside chub are two distinct species, the American
Fisheries Society now recognizes the two species as such (Jelks et al.
2008, p. 390). Because northern leatherside chub is an acknowledged
species, it is a listable entity under the Act.
The northern leatherside chub is a small fish, less than 150
millimeters (mm) (6 inches (in.)) in length, that received its common
name from the leathery appearance created by small scales on a trim,
tapering body (Sigler and Sigler 1996, p. 78; UDWR 2009, p. 26). It has
rounded dorsal and anal fins, each with eight fin rays (Sigler and
Sigler 1996, p. 78). Typically, the northern leatherside chub is bluish
above and silver below, but orange to red coloration may occur on some
fins (Sigler and Sigler 1996, p. 78). Males also have a golden-red
speck at the upper end of the gill opening and between the eyes and the
upper jaw (Sigler and Sigler 1996, p. 78).
Two characteristics that distinguish northern and southern
leatherside chubs from each other are cranial shape and size-at-age
(UDWR 2009, p. 26). Northern leatherside chub have deeper heads with
shorter snouts (Johnson et al. 2004, p. 850) and are typically 15
percent smaller than southern leatherside chub of the same age, with
northern leatherside chub reaching total length of approximately 60 mm
(2.4 in.) at age 2 and 71 mm (2.8 in.) at age 3 (Belk et al. 2005, pp.
177, 181).
Life History
Before 1995, the life history of the leatherside chub was not well
known, with just a few observations of age, growth, or reproduction
(Johnson et al. 1995, p. 183). Investigations of populations now known
as southern leatherside chub demonstrated the species could live up to
8 years and reached sexual maturity at age 2 (Johnson et al. 1995, p.
185). Further work corroborated that the majority of northern
leatherside chub also mature at age 2, but some not until age 4 (Belk
et al. 2005, p. 181).
The bulk of our reproductive knowledge about this species comes
from the hatchery setting, where successful propagation has occurred.
Northern leatherside chub produce translucent, whitish fertilized eggs
that are adhesive and can clump together or adhere to substrate
(Billman et al. 2008a, p. 277). In natural populations, eggs typically
hatch in late June (Belk et al. 2005, p. 181), but in hatchery
conditions, spawning occurs between April and September (Billman et al.
2008a, p. 276). In controlled hatchery conditions, eggs hatch between 4
and 6 days to produce fry that still reside in the substrate (Billman
et al. 2008a, p. 277). Six days after hatching, fry emerge from the
substrate, and by 40 days after hatching most have tripled in length to
approximately 16 mm (0.63 in.) (Billman et al. 2008a, p. 277).
In the hatchery setting, spawning overwhelmingly occurs over cobble
substrate (which provides interstitial space for eggs) and in higher
velocity flows (which provide oxygen and remove fine sediment) (Billman
et al. 2008a, p. 277). These conditions indicate main channel riffle or
run habitats are likely the natural location of northern leatherside
chub spawning.
Northern and southern leatherside chub have similar, relatively
broad diets, with aquatic and terrestrial insects and crustaceans
accounting for 75 percent of their consumption in one study (Bell and
Belk 2004, p. 414). Aquatic and terrestrial insects dominated the
autumnal northern leatherside chub diet at the Sulphur Creek sample
site (Bell and Belk 2004, p. 414). The species foraged on a wide
variety of prey items common to both the substrate and stream drift
(Bell and Belk 2004, p. 414). However, it is likely

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that the species' diet varies throughout the year and at different
locations based on available food (Bell and Belk 2004, p. 414). The
study results indicate that the species' diet overlaps with other
native and nonnative fish, including sculpins (Cottidae family),
shiners (Cyprinids), and cutthroat (Oncorhynchus clarkii) and brown
(Salmo trutta) trout, suggesting possible competitive interactions
(Bell and Belk 2004, p. 414).
Habitat
Northern leatherside chub inhabit small desert streams between
elevations of approximately 1,250 to 2,750 meters (m) (4,100 to 9,000
feet (ft)) in the Bear, Snake, and Green River subregions (as defined
by the U.S. Geological Survey's (USGS) National Hydrography Dataset
(NHD)) (Idaho Department of Fish and Game (IDFG) 2005, p. 1). Streams
of this nature encounter extreme seasonal and annual physical
conditions because of variation in temperature and precipitation
(Wilson and Belk 2001, p. 40). Therefore, northern leatherside chub
must endure cold winters and hot summers (water temperature from 0 to
25 [deg]C (32 to 77 [deg]F); high, turbid spring runoff and low, clear
summer base flows; and periodic droughts that reduce water in streams
(Wilson and Belk 2001, p. 40). It is likely that enduring these
variable extreme habitat conditions adapted northern leatherside chub
to tolerate varied habitat conditions.
Most habitat descriptions are the result of investigations before
leatherside chub was divided into two species, but habitat descriptions
for the northern leatherside chub can be evaluated based on their
distinct geographic range. Summer water temperature of occupied habitat
is reportedly 10 to 23 [deg]C (50 to 73.4 [deg]F), but the current
belief is that northern leatherside chub's range is actually restricted
to 15.5 to 20 [deg]C (59.9 to 68 [deg]F) (UDWR 2009, p. 27). The
species does not persist in lakes or reservoirs (UDWR 2009, p. 27).
Northern leatherside chub prefer low water velocities (15 to 23
centimeters per second (cm/s) (0.5 to 0.75 feet per second (fps)), and
their probability of occurrence decreases at higher velocities (UDWR
2009, p. 40). Water velocity and temperature generally limit the
northern leatherside chub from occupying high headwater streams. Recent
habitat investigations show that northern leatherside chub habitat
associations are consistent with the results for the southern species
(Belk and Wesner 2010, p. 12), allowing us to consider habitat data for
southern leatherside chub as generally acceptable for northern
leatherside chub.
Distribution
Recent and ongoing investigations continue to revise the current
and historical distributions of northern leatherside chub by verifying
or invalidating historical specimens, intensely resampling specific
stream reaches suspected to harbor the species, and documenting new
northern leatherside chub occurrences. For this finding, we completed a
white paper summarizing current and historical distributions through
fall 2010 (McAbee 2011, entire). We analyzed current and historical
range at the subbasin level (otherwise known as 8-digit Hydrologic Unit
Code (HUC) in the USGS' NHD or HUC8), and current population locations
at the subwatershed level (otherwise known as 12-digit HUC or HUC12).
We identified population locations in one to multiple subwatersheds,
depending on the perceived interaction between individuals. State
wildlife agencies and universities reviewed the document to ensure that
it summarized their data collection correctly. Information from our
population summary (also known as `white paper') is used throughout
this finding to inform our conclusions (McAbee 2011, entire).
The documented historical range of northern leatherside chub
includes portions of the Bear River subregion that drain to the Great
Salt Lake, and discontinuous subbasins in the Upper Snake River
subregion that eventually drain to the Pacific Ocean (Figure 1; Table
1). It is unclear how this species came to inhabit two presently
unconnected hydrologic regions. Past geologic events associated with
the draining of Lake Bonneville or the connection of the Bear River to
the Snake River as recently as 30,000 years ago (Behnke 1992, p. 134)
are likely responsible for the separation (UDWR 2009, p. 25). The range
of northern leatherside chub has declined over the past 50 years
(Wilson and Belk 2001, p. 36; Johnson et al. 2004, pp. 841-842; UDWR
2009, p. 24), and the verified current range of the species is now
limited to five of the eight documented historical subbasins (Table 1).
However, additional survey efforts are planned or ongoing.
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Table 1--Documented Range of the Northern Leatherside Chub by Subbasin
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In addition to the historical range, two populations are now known
from the Upper Green River subregion in the Colorado River region
(Table 1). It is possible that these occurrences are the result of
human introductions. However, genetic analysis is necessary to confirm
the origin of these populations, and this information is not yet
available. For the purposes of this finding, we acknowledge these
populations' conservation value.
Because verifiable, historical records are sparse, we are unable to
produce a large-scale historical range boundary with this information.
Therefore, we rely on the known, verified collections to analyze the
status of the species.
Northern leatherside chub are difficult to identify in the field
because they can be confused with other species with similar
appearances. Therefore, many collections were incorrectly classified as
northern leatherside chub, when in fact they were later verified as
Utah chub (Gila atraria), speckled dace (Rhinichthys osculus), or
redside shiner (Richardsonius balteatus). Ichthyologists at Brigham
Young and Idaho State Universities worked to verify historical records
and validate recent collections in order to authenticate data. As a
result, many previously accepted collections were refuted, leading to a
clearer understanding of the species' range (Northern Leatherside Chub
Conservation Team 2010, p. 4). In fact, many subbasins once identified
as part of the species' current or historical range are now either
questioned or invalidated (Table 2). While we expect that the northern
leatherside chub's natural distribution is more continuous than
verifiable historical and current data indicate, we have no specific
data to describe this range other than what is presented in this
finding (Figure 1; Table 3).

Table 2--Suspected Subbasins That Are No Longer Considered Northern Leatherside Chub Current or Historical Range
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NATIONAL HYDROGRAPHY DATASET LOCATIONS
Status
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Subregion (code) Subregion code and name
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Upper Snake River (1704)............ 17040207 Blackfoot River........ Historical specimen
incorrectly classified; No
verified records.
17040210 Raft River............. Unvouchered historical
record not corroborated by
recent sampling; No
verified records.
17040213 Salmon Falls Creek..... Unvouchered recent record
not corroborated by
repeated sampling; No
verified records.
17040219 Big Wood River......... Unvouchered recent record
not corroborated by
repeated sampling; No
verified records.
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Middle Snake (1705)................. unknown Bruneau & Snake Rivers. Historical specimens
incorrectly classified; No
verified records.
17050104 Upper Owyhee........... Museum records need to be
checked.
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Great Salt Lake (1602).............. 16020309 Curlew Valley.......... Listed in conservation
agreement, but no
supporting data; No
records.
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Table 3--Extant Populations of Northern Leatherside Chub in 2010
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NATIONAL HYDROGRAPHY DATASET LOCATIONS
----------------------------------------------------------------- POPULATION NAME STATE
Subregion Subbasin
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Bear River............................ Upper Bear.............. Upper Mill/Deadman Creeks.... UT/WY
Upper Sulphur/La Chapelle WY
Creeks.

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Yellow Creek................. UT/WY
Upper Twin Creek............. WY
Rock Creek................... WY
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Central Bear............ Dry Fork Smiths Fork......... WY
Muddy Creek.................. WY
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Snake River........................... Snake Headwaters........ Pacific Creek................ WY
Salt River.............. Jackknife Creek.............. ID
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Goose Creek............. Trapper Creek................ ID
Beaverdam Creek.............. ID
Trout Creek.................. NV/ID
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Green River........................... Upper Green River/Slate North Fork Slate Creek....... WY
Creek.
Blacks Fork............. Upper Hams Fork.............. WY
----------------------------------------------------------------------------------------------------------------

Overall, our identification and confirmation of a northern
leatherside population for this finding required the presence of
multiple age classes, collection of a dense number of fish (more than
five individuals), and documentation of fish collections over multiple
years. Meeting these criteria demonstrated to us that northern
leatherside chub populations were resident, reproducing, and persisting
over time. Within the current range of the northern leatherside chub,
we thus delineated 14 extant populations, spread across the Bear (7),
Snake (5), and Green (2) River subregions (Table 3). Locations where
northern leatherside chub were collected, but were not classified as a
population, are detailed in our white paper analysis (McAbee 2011,
entire).

Bear River Subregion

The Bear River subregion harbors seven extant populations of
northern leatherside chub across two subbasins: Five in the Upper Bear
River subbasin and two in the Central Bear River subbasin (Table 3). We
are aware of the presence of some individual fish upstream (Hayden and
Stillwater Forks) (Nadolski and Thompson 2004, pp. 3, 4, 7; Chase 2010,
pers. comm.) and downstream (mainstem Bear River and lower Sulphur
Creek) (Wyoming Game and Fish Department (WGFD) 2008, pp. 1, 3; Belk
and Wesner 2010, p. 5) of these areas; however, we do not consider
these as populations because they do not meet the definition of a
population outlined above (specifically presence of multiple age
classes and collection of a dense number of fish) due to their low
densities and lack of juvenile fish.
In the Upper Bear River subbasin, the Upper Mill/Deadman Creeks and
Yellow Creek populations harbor dense, reproducing populations of
northern leatherside chub (McKay and Thompson 2010, pp. 4-7). In the
Upper Mill/Deadman Creeks population, approximately 1,000 individuals
per kilometer are found in Deadman Creek (McKay and Thompson 2010, pp.
6-7) and groups occur downstream in Mill Creek in Utah and Wyoming
(Nadolski and Thompson 2004, pp. 3, 7; Belk and Wesner 2010, p. 5). The
Yellow Creek population has groups of individuals from the upper
reaches in Utah downstream through Wyoming and in Thief Creek, a
tributary (Thompson et al. 2008, pp. 8-9; Zafft et al. 2009, p. 3; Belk
and Wesner 2010, p. 5). The Upper Sulphur/La Chapelle Creeks population
above Sulphur Creek Reservoir also harbors abundant northern
leatherside chubs (Zafft et al. 2009, p. 3). This population is likely
isolated by the presence of Sulphur Creek Reservoir, which is
unsuitable habitat and is stocked with predatory nonnative trout (brown
trout before 2000, rainbow trout (Oncorhynchus mykiss) currently) (WGFD
2010, pp. 3-6).
Twin Creek, a large tributary to the Bear River in the Upper Bear
River subbasin, contains two populations of northern leatherside chub:
Rock Creek and Upper Twin Creek. Multiple tributaries to Twin Creek
comprise the Upper Twin Creek population, including Clear Creek and the
North, East, and South Forks of Twin Creek (Belk and Wesner 2010, p. 5;
Colyer and Dahle 2010, p. 5). These populations can presumably interact
but are likely isolated from all other populations because sampling has
failed to detect downstream emigrants (McKay and Thompson 2010, p. 18).
In the Central Bear River subbasin, the Smiths Fork area harbors at
least two large populations: Dry Fork Smiths Fork and Muddy Creek. Both
contain hundreds of individuals (Colyer and Dahle 2007, p. 8; Belk and
Wesner 2010, p. 5). Individual fish from this population can disperse
downstream, but many perish in irrigation canals before reaching the
mainstem Bear River (Roberts and Rahel 2008, pp. 951, 955).

Snake River Subregion

The Snake River subregion contains eight subbasins with historical
northern leatherside chub observations (UDWR 2009, pp. 44, 48).
However, biologists have reexamined museum records, resampled stream
reaches with presumed past observations, and refined the identification
key for the species. As a result, four of the eight subbasins, the
Raft, Big Wood, and Blackfoot Rivers, and Salmon Falls Creek, with past
records were downgraded to ``unlikely to have contained or to contain
northern leatherside chub'' (Table 2). One subbasin has verified
historical records but no current records (Little Wood River), and is
thus considered extirpated unless new information is obtained.
The remaining three subbasins with verified current records are
Goose Creek, Snake Headwaters, and Salt River (Table 1; McAbee 2011, p.
2). Within the Goose Creek subbasin, we know of three reproducing
populations at Trapper, Beaverdam, and Trout Creeks. All three
populations have persisted over the past 10 to 15 years (Grunder et al.
1987, p. 80; Wilson and Belk 1996, p. 17; Keeley 2010, pp. 3-29).
Trapper Creek is isolated from the other two by Oakley Reservoir, but
there are no barriers between Trout and Beaverdam Creeks, and the
populations likely interact. Collections of single northern

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leatherside chub individuals in mainstem Goose Creek (Keeley 2010, pp.
24-29) indicate individuals may be dispersing from these two
populations. Recent collections of individuals in Pole Creek in the
Goose Creek subbasin suggest a population may occur in this tributary
as well (Grunder 2010, p. 3). However, no juvenile fish were collected,
and this is the first year northern leatherside were documented in this
reach (Keeley 2010, pp. 6-11). Although these collections may
constitute a colonization event, we do not consider Pole Creek a
population in this finding because multiple age classes were not
present (demonstrating the area has not shown successful reproduction
or recruitment).
The single population in the Snake Headwaters subbasin is Pacific
Creek, which has persisted since its discovery in the 1950s (Grand
Teton National Park 2009, pp. 1-2; Zafft et al. 2009, pp. 2-5). In the
Salt River subbasin, a single population is found in Jackknife Creek
and its tributaries (Isaak and Hubert 2001, pp. 26-27; Keeley 2010, pp.
45-60). The Pacific Creek population is separated from the Jackknife
Creek population by large stream distances and large reservoirs, making
individual dispersal between the two populations unlikely. In addition,
both the Pacific Creek and Jackknife Creek populations are isolated
from the Goose Creek subbasin by upwards of 350 stream-kilometers (km)
and many large reservoirs.

Green River Subregion

There are two northern leatherside chub populations in the Green
River subregion, one each in the Upper Green River/Slate Creek and
Blacks Fork subbasins (Table 3). However, based on the lack of
historical collections in the Green River subregion, the lack of a
documented natural connection between the Green River subregion and the
Bear or Snake River subregions, and the prevalence of human
translocations of fish, we determine that it is unlikely that this is
the species' native range. The first population was identified in 1988
in North Fork Slate Creek (WGFD 1988 in Zafft et al. 2009, p. 2), and
represented the first population outside the Bear or Snake River
subregions. This population is approximately 30 km (18 mi) east of the
Bear and Snake River subregions, making it close enough to be the
result of a human introduction. The Upper Hams Fork population was
later identified (Wheeler 1997 in Zafft et al. 2009, p. 3), and is
located approximately 35 km (22 mi) northeast of the North Fork Slate
Creek population. In addition, this population is just across the
subregion boundary with the Dry Fork Smiths Fork population, making it
even more possible that the population is the result of a human
introduction. We also are aware of individual fish in the nearby West
Fork of the Hams Fork in 2006 (Zafft et al. 2009, p. 3), which we
include as part of the Upper Hams Fork population because they can
interact.
These two populations indicate that northern leatherside chub are
persisting in the Green River subregion. Whether these populations are
native, or are recent human introductions, has yet to be resolved.
Genetic analysis to answer this question is planned for completion in
the near future, and will hopefully resolve this question. Until proof
can be presented that these populations are not native, their
conservation value to the species must be considered.
It is worth noting that genetic analysis of southern leatherside
chub collections in the Fremont River (Green River subregion)
demonstrated that they were not native, but rather a genetic match to
an East Fork Sevier River population (Barrager and Johnson 2010, p. 7).
These results show that a successful human translocation of a surrogate
species has occurred, and is possible for the northern leatherside
chub.
In summary, 14 extant northern leatherside chub populations persist
across 3 subregions: 7 populations in the Bear River subregion; 5
populations in the Snake River subregion; and 2 populations in the
Green River subregion (Figure 1, Table 1). Land ownership is comprised
of privately owned land (31.5 percent in the States of Idaho, Nevada,
Utah, and Wyoming), as well as lands managed by BLM (30 percent), NPS
(3.5 percent), USFS (30.5 percent), and the States of Wyoming (4.3
percent) and Idaho (0.04 percent) (Service 2011, pp. 11-17). We will
investigate threats to these extant populations in the remainder of
this finding.

Summary of Information Pertaining to the Five 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 our 12-month finding on the petition we considered and
evaluated the best available scientific and commercial information.
Information pertaining to the northern leatherside chub in relation to
the five factors provided in section 4(a)(1) of the Act is discussed
below.

Factor A. The Present or Threatened Destruction, Modification, or
Curtailment of Its Habitat or Range

The following potential threats that may affect the habitat or
range of northern leatherside chub are discussed in this section,
including: (1) Livestock grazing; (2) oil and gas development; (3)
mining; (4) water development; (5) water quality; and (6) fragmentation
and isolation of existing populations.
Livestock Grazing
Livestock presence generally disturbs streamside and instream
habitats, particularly in the arid west where riparian and stream
habitats are fragile ecosystems (Kauffman and Krueger 1984, p. 431;
Helfman 2007, p. 102). Livestock grazing is especially detrimental to
riparian habitats because livestock spend disproportionately more time
near water (Helfman 2007, p. 102). They typically eat and trample
riparian vegetation and compact soil, which leads to impacts that
include increased sediment inputs from runoff, nutrient loading from
livestock waste, higher stream temperatures from lack of vegetation
shading, and reduction in invertebrate abundance (Kauffman and Krueger
1984, p. 432; Wohl and Carline 1996, p. 264; Stoddard et al. 2005, p.
8). These impacts combine to degrade habitats for many fish species,
especially species requiring cool, clear water and gravel substrate,
such as salmonids (Helfman 2007, p. 34).
However, some species, such as the northern leatherside chub, can
tolerate certain habitat changes and persist despite disturbed
conditions. Increased sediment may alter a fish community and allow for
domination by species that thrive or contend well with sandy substrates
(Sutherland et al. 2002, pp. 1801-1802) (see Water Quality section for
specific discussion of sedimentation and northern leatherside chub).
Similarly, increased water temperature also may alter the distribution
of species, forcing out cold-water species,

[[Page 63451]]

and allowing for warm-water species to enter a habitat (Field et al.
2007, p. 631). Northern leatherside chub apparently can tolerate
certain disturbances, largely because they can survive extreme
environmental conditions to which they are evolutionarily adapted (Belk
and Johnson 2007, p. 70), such as high water temperatures (Isaak and
Hubert 2001, p. 27; Wilson and Belk 2001, p. 39), with a critical
thermal maximum of approximately 30 [deg]C (86 [deg]F) (Billman et al.
2008b, p. 463) and persist in large numbers in areas deemed degraded
(Muddy Creek and Upper Twin Creek). However, we do not have specific
data indicating their tolerances to all water quality conditions. While
habitats impacted by grazing may not be preferred, populations of
northern leatherside chub persist in locations deemed degraded and
impaired.
For example, in the Bear River subregion, the Upper Twin Creek
population persists even though overgrazing has reduced the riparian
vegetation cover (Colyer and Dahle 2010, pp. 16, 19) to the point that
the streams are classified as degraded (BLM 2011, entire). In the same
subregion, Muddy Creek is another example of a dense northern
leatherside chub population that persists (Colyer and Dahle 2007, Table
6) despite altered conditions from overgrazing that result in a very
wide, shallow channel and degraded riparian habitats (BLM 1999, p. 7;
BLM 2007a, pp. 1-2; Prichard 1998, p. 8; BLM 2005, p. 5). In the Snake
River subregion, populations persist in Beaverdam and Trapper Creeks
although the water quality in both streams is impaired, most likely as
the result of overgrazing (Lay 2003, pp. 69-70, 125). However, it is
worth noting that impacts from grazing affect Beaverdam and Trapper
Creeks in qualitatively different ways (high suspended sediment) than
Muddy and Upper Twin Creeks (reduced riparian cover).
Data indicate that some level of livestock grazing occurs across
the entire range of the northern leatherside chub and near all existing
populations (Service 2011, pp. 18-24). Because of the prevalence of
grazing across the western United States, the species will likely
encounter livestock grazing effects. However, we expect effects from
livestock grazing will decrease over time on Federally managed lands as
management agencies address livestock grazing practices. For example,
the U.S. Forest Service (USFS) recently implemented changes in the
grazing management on the Goose Creek grazing allotment that occurs in
the upstream portions of Beaverdam and Trout Creeks (Northern
Leatherside Chub Conservation Team 2011, p. 3). On a broader scale,
Bureau of Land Management (BLM) guidelines in Idaho (BLM 1997, p. 4,
Standard 2), Wyoming (BLM 2007c, p. 1, Standard 2),
Utah (BLM 2009, p. 1, Standard 1b), and Nevada (BLM 2007b, p.
1, Standard 2) require all streams to have riparian health
consistent with natural, functional habitats, indicating that grazing
impacts will be improving on BLM lands. Upstream land ownership for all
but three occupied sub-watersheds (11 of 14) is over 50 percent
federally owned, demonstrating the importance of Federal land
management for northern leatherside chub (see detailed discussion of
land ownership under Factor D below).
In summary, there is no apparent indication that grazed areas are
negatively impacting existing populations of northern leatherside,
although grazing has likely affected water quality (discussed later).
Populations of northern leatherside chub occur in a wide variety of
habitat conditions, from unaltered locations to those with heavily
altered riparian conditions impacted by livestock grazing practices. In
fact, some of the densest populations occur in areas that are heavily
grazed. Also, there is evidence to indicate that livestock grazing
impacts will be declining in the future, as more sustainable rangeland
management practices are applied. We found no information that grazing
may act on this species to the point that the species itself may be at
risk, nor is it likely to become so.
Oil and Gas Development
Oil and gas exploration and development can impact fish habitats,
primarily through degraded watershed health. Increased land disturbance
from roads and pads reduce water quality because of increased sediment
loads (WGFD 2004, p. 25; Matherne 2006, p. 1). Road culverts also can
fragment fish habitats if they are designed in a way that impedes fish
migration (Aedo et al. 2009, p. 2). Drilling operations often require
water depletions from local water sources and can result in accidental
spills of contaminants into fish habitat (Stalfort 1998, p. ES-2; Etkin
2009, pp. 35-42). Accumulations of contaminants, such as hydrocarbons
and produced water (water locked away in formation with oil and gas
that is typically not suitable for human or wildlife use), can result
in lethal or sublethal impacts across the entire aquatic food chain,
including sensitive fish species (Stalfort 1998, Section 4). Water
depletions can reduce or eliminate aquatic habitat, creating multiple
negative effects (see Water Development, below).
To analyze the potential impacts from oil and gas development, we
investigated past and present levels of development and the potential
for future development in occupied populations. We summarized the
analysis in an internal white paper (Hotze 2011, pp. 1-8) and reference
the results throughout this finding. Data sources for the investigation
included Bureau of Land Management Resource Management Plans (BLM 1985,
entire; BLM 2010, entire); State databases of oil and gas development
(Hess et al. 2008, entire; Utah Division of Oil, Gas, and Mining 2009,
entire; Wyoming Oil and Gas Conservation Commission 2009, entire; State
of Idaho 2011, entire); and energy development maps (Garside and Hess
2007, map; Energy Information Administration (EIA) 2009a, map; EIA
2009b, map; EIA 2011, entire).

TABLE 4--Summary of Oil and Gas Development in Extant Northern Leatherside Chub Populations
----------------------------------------------------------------------------------------------------------------
National hydrography dataset locations Overlap with
-------------------------------------------------- Active oil & known coalbed
Population name State gas wells methane
Subregion Subbasin (inactive) reserves (%)
----------------------------------------------------------------------------------------------------------------
Bear River.................... Upper Bear....... Upper Mill/ UT/WY 0 (6) 4
Deadman Creeks.
Upper Sulphur/La WY 2 (1) 47
Chapelle Creeks.
Yellow Creek.... UT/WY 28 (63) 25
Upper Twin Creek WY 0 (0) 9

[[Page 63452]]

Rock Creek...... WY 0 (1) 131
Central Bear..... Dry Fork Smiths WY 0 (0) 0.1
Fork.
Muddy Creek..... WY 0 (0) 0
Snake River................... Snake Headwaters. Pacific Creek... WY 0 (0) 0
Salt River....... Jackknife Creek. ID 0 (0) 16.6
Goose Creek...... Trapper Creek... ID 0 (0) 0
Beaverdam Creek. ID 0 (0) 0
Trout Creek..... NV/ID 0 (0) 0
Green River................... Upper Green River/ North Fork Slate WY 0 (5) 32
Slate Creek. Creek.
Blacks Fork...... Upper Hams Fork. WY 0 (0) 0
----------------------------------------------------------------------------------------------------------------

We found that throughout the range of northern leatherside chub,
neither active development nor potential for future development of oil
and gas are common, with both being limited to one localized area, the
Yellow Creek population in the Bear River subregion (Table 4) (Hotze
2011, pp. 1-8). A quarter of the Yellow Creek population overlaps with
proven Federal oil and gas reserves, mostly in the western and northern
portions of the subwatershed (EIA 2009a, map; Hotze 2011, p. 5).
Current and past well activity follow this overlap, with 63 inactive
and 28 active wells in the population's subwatershed, mainly near the
occupied areas of Thief Creek and lower Yellow Creek in Wyoming (Hotze
2011, p. 2). No development activity has occurred in the upstream
portions of Yellow Creek, which contain high densities of northern
leatherside chub, and no proven Federal oil and gas reserves occur
there. A quarter of the Yellow Creek population overlaps with coalbed
methane reserves, in the eastern-central portion in Wyoming, suggesting
the potential for development (Hotze 2011, p. 7).
The populations in the northern portions of the Bear River
subregion have seen little past or current development and have a low
probability of future development. The Twin Fork drainage has only one
inactive well across the Rock and Upper Twin Creek populations (Hotze
2011, p. 2). A small portion (less than 1 percent) of the Rock Creek
population overlaps with the Collett Creek field, which contains proven
Federal oil and gas reserves (Hotze 2011, pp. 4-5). The Smiths Fork
drainage is north of the Wyoming Thrust Belt (an optimal geologic
formation for retrieving oil and gas resources), so development of oil
reserves has not historically occurred in the Muddy Creek and Dry Fork
Smiths Fork populations, and is not likely to occur in the future
(Hotze 2011, p. 2). Similarly, there is very little overlap between
these two populations and known coalbed reserves (less than 1 percent
of the Dry Fork Smiths Fork population) (Hotze 2011, p. 7), making it
unlikely that coalbed methane development will take place in these
populations.
In the remainder of the Bear River subregion, past and current
resource development is rare, but resource potential exists. The Upper
Sulphur/La Chapelle Creeks population has only one inactive and two
active wells, but half of the population area overlaps with coalbed
methane reserves (Hotze 2011, pp. 2, 7). However, the area has a low
potential for resource extraction demonstrated by the low presence of
current or past wells and the distance to the closest producing well.
The Upper Mill/Deadman Creeks population has only six inactive wells,
all in the Utah portion of the population's subwatershed (Hotze 2011,
p. 2). Less than 5 percent of the Upper Mill/Deadman Creeks population
overlaps with coalbed methane reserves, all in the most downstream
reaches that do not contain northern leatherside chub (Hotze 2011, p.
7).
The Snake River subregion populations occur in areas that do not
have active development and are characterized as low potential for
future development (Hotze 2011, pp. 1-2). Currently, all populations in
the Goose Creek subbasin (Trout, Trapper, and Beaverdam Creeks) are in
areas open for oil and gas leasing, but there are no producing wells in
either the Idaho or Nevada portions (Hotze 2011, p. 2). Further east,
there is potential for development of the Idaho-Wyoming Thrust Belt in
the Jackknife Creek population, but the probability of discovering and
developing oil in this area is considered low by BLM (BLM 2010, p. Q-
1). No wells are currently found in the Jackknife Creek population
(Hotze 2011, p. 2). Finally, the Pacific Creek population may overlap
with the Jackson Hole coalbed methane field, but management by Grand
Teton National Park makes it unlikely that development of these
resources will take place (Hotze 2011, p. 2).
In the portions of the Green River subregion occupied by northern
leatherside chub, there is little active or historical development of
any kind and minor potential for future development exists, chiefly
from coalbed methane reserves. The Upper Hams Fork is outside of any
known coalbed reserves, the population is north of the Wyoming Thrust
Belt and west of the Wyoming Overthrust coalbed reserves (Hotze 2011,
pp. 2, 7). As a result, it has no active or inactive wells within its
boundary, and we consider future development potential in this
population negligible (Hotze 2011, p. 2). The North Fork Slate Creek
population has only five inactive wells within its boundary, but
overlaps with the Wyoming Overthrust coalbed reserves in the upstream
third of the population (Hotze 2011, pp. 2, 7). It is possible that
development could occur in this population, but we have no data to
indicate that development is planned or imminent. Also, without
environmental planning for this development, we cannot say what impacts
the development would have on northern leatherside chub.
To summarize, past, present, and future oil and gas development is
likely to impact one population of northern leatherside chub, Yellow
Creek in the Bear River subregion, and only in the downstream half.
Only two populations overlay with proven Federal oil and gas reserves,
Yellow and Rock Creeks (Table 4). The Rock Creek overlap is
insignificant, accounting for less than 1 percent of the population's
subwatershed. However, the Yellow

[[Page 63453]]

Creek overlap is sizable, at approximately a quarter of the
population's subwatershed. Correspondingly, only Yellow Creek has
measurable levels of current energy development at a moderate scale.
Because the impacts to Yellow Creek are downstream of a large portion
of the occupied area within the population boundary, we find oil and
gas development does not threaten the persistence of the Yellow Creek
population. Although some resource potential is found throughout the
range of the species, future development is unlikely to occur or impact
all but one population (Yellow Creek). Oil and gas development impacts
only a small portion of the species' total range, and the impacted
population will likely persist in upstream reaches. We found no
information that oil and gas development may act on this species to the
point that the species itself may be at risk, nor is it likely to
become so.
Mining
Hardrock mining for such materials as gold, copper, iron ore,
uranium, and others is the most common mining activity in the western
United States (Trout Unlimited 2011, p. 1). Underground and surface
mining activities have the potential to negatively affect fish species
by releasing solid wastes and contaminated mine water (Helfman 2007,
pp. 160-161; Trout Unlimited 2011, p. 1).
Solid waste from mining includes overburden, which is the topsoil
and surface rock that is above a mineral deposit; waste rock, which is
the low grade ore that surrounds a mineral deposit; and tailings, which
are the fine-grained materials that are left over from the processing
of raw ore (Trout Unlimited 2011, p. 1). Abandoned and currently
operating mine sites can impact downstream fish species from the
sedimentation that results from erosion of waste rock (Helfman 2007,
pp. 112, 113) (see Water Quality section for specific discussion of
sedmentation and northern leatherside chub).
Contaminated mine water is the ground or surface water that
accumulates and is discharged from a mine or its associated waste rock
piles (Trout Unlimited 2011, p. 1). This water can cause deleterious
effects to fishes via acidification and heavy metal contamination
(Helfman 2007, pp. 160-161, 168-169). Stream acidification results from
drainage of waters from mines or their waste rock by-products. This
water is highly toxic because the associated low pH harms fish
respiratory function and can impact reproduction rates and rearing
outcomes (Helfman 2007, p. 159). Low pH in aquatic systems also can
negatively affect aquatic plants and macroinvertebrates and thereby
reduce food sources and habitat for fish (Helfman 2007, pp. 160-161;
Trout Unlimited 2011, p. 1). Heavy metal contamination of aquatic
habitats also can result from mine water that is discharged from mines
or that infiltrates and then runs out of waste rock or tailings piles.
Heavy metals such as lead, copper, zinc, cadmium, mercury, aluminum,
iron, manganese, and selenium can be toxic to fishes at low
concentrations and can ultimately interfere with embryonic development,
digestion, respiration, general growth, and survival (Helfman 2007, pp.
160, 161; Trout Unlimited 2011, p. 1).
We assessed mining activity within the range of northern
leatherside chub by reviewing mining location data as reported by State
agencies and in GeoCommunicator, the publication Web site for the
National Integrated Land System as operated by a joint venture between
the BLM and USFS (http://www.Geocommunicator.gov/GeoComm, Mining
Claims). This information shows that uranium, coal, and non-coal (all
other mine types) were prospected for in much of the northern
leatherside chub range (Service 2011, pp. 25-32). However, the majority
of these mines or prospects are historical and are no longer in
operation (Service 2011, pp. 25-32).
In the Bear River subregion, there are no abandoned mines, active
mines, or mining claims in the Upper Mill/Deadman Creeks, Upper
Sulphur/La Chapelle Creeks, Yellow Creek, or Muddy Creek populations
(Service 2011, pp. 28, 30). In the Rock Creek drainage, there are 11
quarter sections with 1 to 5 mining claims each; however, these are
located downstream of northern leatherside chub occupied habitat and
are not being actively developed (Service 2011, p. 29). The Upper Twin
Creek population has one abandoned mine about 2 miles (mi) upstream of
occupied habitat on North Fork Twin Creek, and approximately four
abandoned mines upstream of occupied habitat on East Fork Twin Creek
(Service 2011, p. 29). Also, a small portion of the headwaters of the
Upper Twin Creek population is under an active coal lease; however, the
active mining associated with this lease is found on the other side of
the watershed boundary, meaning impacts will not affect northern
leatherside chub (WSGS 2009, map). We have no information to indicate
that any of these abandoned mines are having an effect on adjacent
northern leatherside chub in the Upper Twin Creek population. In the
Dry Fork Smiths Fork population, there are eight quarter sections with
one to five mining claims; however, these are located primarily
downstream of northern leatherside chub occupied habitat, are not
developed, and thus should not have an effect on occupied habitat
(Service 2011, p. 30).
In the Snake River subregion, there are no abandoned mines, active
mines, or mining claims within northern leatherside chub habitats in
the Trout or Jackknife Creek populations (Service 2011, pp. 25, 26).
The Trapper Creek and Beaverdam Creek populations have several
abandoned mines of lignite and uranium prospects/deposits that are
adjacent to northern leatherside chub occupied habitat (about four to
five sites in each drainage) (Service 2011, p. 25). Because prospects
and identified deposits usually involve a small disturbance such as a
shallow hole or a short adit (an entrance to an underground mine which
is horizontal or nearly horizontal), we determine these features are
having negligible impact on northern leatherside chub occupied habitat.
In the Pacific Creek population where northern leatherside chub are
found, there are 11 quarter sections with 1 to 5 mining claims each
(Service 2011, p. 27). These mining claims occur upstream of northern
leatherside chub occupied habitat; these claims are not developed, and
we have no information to suggest that these will be developed. At this
time we have no information to suggest that any of these abandoned
mines or mining claims are having a significant effect on adjacent
northern leatherside chub at an individual or population level.
In the Green River subregion, neither the Slate Creek nor the Upper
Hams Fork populations have abandoned mines, active mines, or mining
claims (Service 2011, pp. 31-32). Thus, there are no effects from
mining on northern leatherside chub populations in these areas.
In summary, recent examination of mining activity in northern
leatherside chub habitat has determined that mining-related impacts are
limited. Mining was historically prevalent in occupied portions of the
Bear and Snake subregions, but largely absent in occupied portions of
the Green River subregion. Some mines do still operate in northern
leatherside chub populations. However, we have no information at this
time to suggest that mining activities are having an effect on water
resources or habitat of northern leatherside chub. We found no
information that mining activities may act on this species to the point
that the

[[Page 63454]]

species itself may be at risk, nor is it likely to become so.
Water Development
Water development in western North America has the potential to
impact native fish species by degrading aquatic habitats and altering
natural ecological mechanisms (Minckley and Douglas 1991, p. 15; Naiman
et al. 2002, p. 455). Water development can affect aquatic species
through desiccation (drying that results in loss of habitat), reduction
in available habitat from reduced flows, reduced population
connectivity, and decreases in water quality (e.g., higher water
temperatures in summer months because of lower water volume or
increased concentration of pollutants). In addition, water diversion
structures often entrain (pull in and trap) fish into canal systems
along with irrigation water, placing fish in lethal habitats because
water supplies are typically shut off at the end of the irrigation
season (Roberts and Rahel 2008, p. 951).
The development of water resources in the Bear, Snake, and Green
River subregions has led to the conversion of some northern leatherside
chub stream habitats into seasonally dewatered channels (complete
absence of flowing water) (Nadolski and Thompson 2004, p. 4; Thompson
et al. 2008, p. 20; McKay et al. 2009, p. iv; Yarbrough 2011, pers.
comm.), representing a complete loss of habitat in some areas. In the
following analysis, we consider the impact of complete dewatering and
entrainment on each northern leatherside chub population. We do not
consider impacts of reduced water volume for each population because
leatherside chub have a broad tolerance of extreme environmental
conditions (Belk and Johnson 2007, p. 70) and have persisted in a
number of locations where low water levels occurred. Leatherside chub
are adapted to periodic low water conditions and can survive in remnant
pools for several weeks after the water flow is completely eliminated
(Belk and Johnson 2007, p. 70). Therefore, complete dewatering
represents the highest risk for mortality of individuals and represents
the primary barrier for movement. Similarly, entrainment creates the
risk of direct mortality, as entrained fish, especially northern
leatherside chub, are not expected to survive in irrigation canals.

Dewatering of Streams

We determined occurrences and temporal extent of recent dewatering
events in occupied populations through agency reports and expert
accounts. In recent, recorded history, no known dewatering events
occurred near 8 of the 14 populations: Upper Mill/Deadman Creeks
(Thompson 2011, pers. comm.); Dry Fork Smiths Fork (BLM 2002, p. B-7);
Muddy Creek (Henderson 2011, pers. comm.); Pacific Creek (Clark et al.
2004, pp. 26-29; O'Ney 2011, pers. comm.); Jackknife Creek (Lyman 2011,
pers. comm.); Trapper Creek (Bisson 2011, pers. comm.); Trout Creek
(Lay 2003, p. 8); and Upper Hams Fork (Yarbrough 2011, pers. comm.). As
a result, we determine that these populations are not threatened by
current water development.
However, six northern leatherside populations did experience
complete dewatering events in areas adjacent to or within their known
habitat and we further analyzed effects to these populations (Table 5).
All dewatering events are seasonal in nature and occur in mid to late
summer (Nadolski and Thompson 2004, p. 4; Thompson et al. 2008, p. 20;
McKay et al. 2009, pp. 20-21), when dry weather and irrigation
pressures are highest. We will address dewatering conditions and the
population response for five population areas (two populations, Rock
and Upper Twin Creek, are experiencing the same nearby dewatering, so
will be considered together): (1) Upper Sulphur/La Chapelle Creeks; (2)
Yellow Creek; (3) Rock and Upper Twin Creeks, all in the Bear River
subregion; (4) Beaverdam Creek in the Snake River subregion; and (5)
North Fork Slate Creek in the Green River subregion.

Table 5--Northern Leatherside Chub Populations That Have Encountered Past Dewatering Events and the Nature of
These Events
----------------------------------------------------------------------------------------------------------------
National hydrography dataset locations
------------------------------------------------------------ Population Nature of dewatering event
Subregion Subbasin
----------------------------------------------------------------------------------------------------------------
Bear River......................... Upper Bear............ Upper Sulphur/La Dewatering upstream in
Chapelle Creeks. headwaters & downstream
near reservoir; No threat
to population.
Yellow Creek.......... In downstream portion;
Reproduction still occurs
locally & upstream
portions unaffected; No
threat to population.
Upper Twin Creek...... Downstream of both
Rock Creek............ populations; Does not
prevent movement between
populations; No threat to
populations.
Snake River........................ Goose Creek........... Beaverdam Creek....... In downstream portion;
Population sustains in
perennial portion but
becomes isolated; No
threat to population.
Green River........................ Slate Creek........... North Fork Slate Creek Downstream portions are
intermittent but local
areas perennial; No threat
to population.
----------------------------------------------------------------------------------------------------------------

Irrigation demands periodically dewater portions of Upper Sulphur
Creek directly upstream of Sulphur Reservoir (Amadio 2011, pers.
comm.), possibly preventing the migration of northern leatherside chub
between the two occupied areas of the Upper Sulphur/La Chapelle Creeks
population in the Bear River subregion. Additionally, headwater
portions of this area were dewatered in Utah in 2007 (Webber 2008, p.
21). However, neither of the dewatered areas are the primary occupied
portion of the population, as northern leatherside chub occupy portions
of Sulphur and La Chapelle Creek in Wyoming upstream of Sulphur Creek
Reservoir, and also downstream of the Utah border. Because dewatering
events do not impact habitats occupied by the population, we conclude
dewatering is not a threat to this population.
The lower reaches of Yellow Creek (Bear River subregion) have low
flows (Thompson et al. 2008, p. 21) or are completely dewatered
(Nadolski and Thompson 2004, p. 4) in the summer months. However,
successful reproduction was evident in nearby upstream portions of
Yellow Creek in 2002, 2005, and 2008 (Thompson et al.

[[Page 63455]]

2008, p. 11). Upper portions of Yellow Creek (from Utah-Wyoming border
to the headwaters) retain water throughout the year and are occupied by
a healthy northern leatherside chub community (Thompson et al. 2008, p.
21). The upper portions of Yellow Creek likely act as a source
population to lower Yellow Creek reaches in years of extreme low water,
and for this reason dewatering is not a threat to this population.
Lower portions of mainstem Twin Creek in the Bear River subregion
are completely dewatered by an irrigation diversion 6.75 km (4.2 mi)
upstream of the Utah-Wyoming border during most of the irrigation
season (Thompson et al. 2008, p. 20). However, northern leatherside
chub are present in several locations upstream of this diversion,
including two extant populations--the Rock and Upper Twin Creek
populations (Belk and Wesner 2010, p. 5; Colyer and Dahle 2010, p. 5).
Northern leatherside chub move through the lower mainstem Twin Creek
(downstream of the diversion) to the mainstem Bear River during
portions of the year when there is water (Thompson et al. 2008, p. 20),
demonstrating the connectivity of these rivers. Because of the
connection between upstream and downstream communities within this
population, and because the upstream communities of Rock and Clear
Creeks are perennial streams (Wyoming Department of Environmental
Quality 2010, p. 15), dewatering is not a threat to these populations.
Beaverdam Creek in the Snake River subregion begins at the
confluence of Left Hand Fork Beaverdam Creek and Right Hand Fork
Beaverdam Creek, with flow being supported by approximately seven
intermittent or ephemeral streams (Lay 2003, p. 99). Lower portions of
Beaverdam Creek are commonly dewatered, leading the Idaho Department of
Environmental Quality (IDEQ) to identify the lower two-thirds of
Beaverdam Creek as intermittent (Lay 2003, p. 99). These sections
include portions near the Emery Ranch and the lowest 3 to 5 km (1.9 to
3.1 mi) of stream from Emery Ranch to Goose Creek (Lay 2003, p. 99).
However, Upper Beaverdam Creek maintains high enough year-round flow to
sustain a cutthroat trout population (Lay 2003, p. 99). Northern
leatherside chub populations also are located in the perennial waters
of upper Beaverdam Creek. The effect of ephemeral dewatering in lower
Beaverdam Creek on northern leatherside chub is to seasonally isolate
this population from other Goose Creek populations in all but the
wettest conditions. Because this population is reproducing and self-
sustaining, we conclude that seasonal dewatering is not currently a
threat to the population.
Portions of Slate Creek in the Green River subregion and its
tributaries are intermittent (Yarbrough 2011, pers. comm.). The South
and Middle Forks of Slate Creek were completely dewatered in July 2003
(WGFD 2009, p. 4). We have little information regarding the demography
of this population, except that several age classes were found in
mainstem Slate Creek and North Fork of Slate Creek during 2003 (WGFD
2009, p. 5). This suggests reproduction and juvenile recruitment is not
impacted by dewatering in adjacent streams. There is no record of
dewatering in the North Fork or mainstem of Slate Creek where northern
leatherside chub are found. Because dewatering occurs downstream of
occupied habitat and reproduction is occurring, we do not consider
dewatering a threat to this population.
While the preceding analysis considered past and current water
development, future water development across the range of northern
leatherside chub may alter the level of impacts. Northern leatherside
chub-occupied subwatersheds in Utah and Idaho are closed to new water
appropriations for any significant consumptive use such as large-scale
irrigation (Dean 2011, pers. comm.; Jordan 2011, pers. comm.). In
contrast, subwatersheds occupied by northern leatherside chub in Nevada
and Wyoming are still open to new water appropriations (Randall 2011,
pers. comm.; Jacobs and Brosz 2000, p. 7). However, we expect minimal
future water development near the only population in Nevada (Trout
Creek) because of the low human population density in the area and
because we are not aware of any new water-intensive land use planned
for the area (Randall 2011, pers. comm.). Although irrigated
agriculture production is the largest water use in Wyoming's three
northern leatherside chub occupied subbasins (Schroeder and Hinckley
2007, p. 5-2), agricultural water use is expected to increase at most
9.2, 5.6, and 5.2 percent for the Green, Bear, and Snake subregions in
Wyoming, respectively, between 2007 and 2037 (Schroeder and Hinckley
2007, pp. 6-2--6-4). We consider these small increases and conclude
that this full development would not be a threat to northern
leatherside chub in Wyoming. Because predictions for future water
development for occupied subbasins indicate water development is either
prohibited or minimal, the available information indicates that the
northern leatherside chub is not threatened throughout all of its range
by water development, nor is it likely to become so.
In summary, while northern leatherside chub are adapted to endure
short-term low water conditions, complete dewatering events can result
in the temporary, seasonal loss of northern leatherside chub habitat.
However, in all of the dewatering events described above, individual
fish are either not locally impacted by dewatering or are able to move
to nearby perennial reaches during the dewatered period. Additionally,
future water development is closed in Utah and Idaho, unlikely in
Nevada, and small-scale in Wyoming. We found no information that
dewatering may act on this species to the point that the species itself
may be at risk, nor is it likely to become so.

Entrainment

Fish encountering unscreened irrigation intake structures are often
injured or killed, primarily through entrainment, the process by which
aquatic organisms are diverted into irrigation structures (Zydlewski
and Johnson 2002, p. 1276; Gale et al. 2008, p. 1541). Entrainment into
irrigation canals is considered a major source of mortality for fish
populations in the western United States because individual fish
entering canal systems typically cannot escape back into stream habitat
(Carlson and Rahel 2007, p. 1335; Roberts and Rahel 2008, p. 951). Near
100 percent mortality is expected once an individual enters an
irrigation canal structure because of the numerous unnatural conditions
in the canals. Individuals entrained into canals are exposed to higher
water temperatures and non-natural substrate (often concrete), while
also becoming easier prey for predatory birds and mammals. Those fish
that survive for long periods ultimately encounter the end of the
irrigation season, when water is often shut off from the canals
(Roberts and Rahel 2008, p. 954), trapping individual fish in
dewatered, lethal conditions. Screening intake structures is the most
common method to minimize entrainment of fish (Zydlewski and Johnson
2002, p. 1276; Moyle and Israel 2005, p. 20; Gale et al. 2008, p.
1541). However, screening facilities must be designed to meet
individual criteria at each location, taking into account the sizes and
swimming abilities of the fish species that will encounter the
structure.
Because they are small minnows with weak swimming abilities, all
northern leatherside chub entrained into canals are expected to die
(Roberts and Rahel

[[Page 63456]]

2008, p. 957). For example, irrigation facilities in the Smiths Fork
River entrained an estimated 195 northern leatherside chub downstream
of two populations, Dry Fork Smiths Fork and Muddy Creek (Roberts and
Rahel 2008, p. 957). Similarly, a large irrigation structure in lower
mainstem Twin Creek entrained native fish species, including northern
leatherside chub, downstream of two populations, Upper Twin and Rock
Creeks (Colyer and Dahle 2010, p. 5). These data show that where
northern leatherside encounter irrigation structures, they are
entrained.
Across the range of northern leatherside chub, irrigation is a
common practice. However, besides the large network of irrigation
intakes in the Smiths Fork (Carlson and Rahel 2007, p. 1336) and Twin
Creek drainages (Colyer and Dahle 2010, p. 6), we know of no other
documented instances of entrainment. In addition, many of the
diversions that could entrain northern leatherside chub in the Twin
Creek drainage were updated with screened, fish-friendly structures by
Trout Unlimited over the past few years (Colyer and Dahle 2010, p. 6),
thereby greatly reducing their threat to northern leatherside chub.
Based on the data from the Smiths Fork and Twin Creek drainages, we
conclude entrainment into canals is likely preferentially targeting
migrating individuals because entrainment is occurring primarily
downstream of populations. This makes entrainment more of an agent of
fragmentation than a threat to extant populations. We expect that when
irrigation diversions are not taking the entire water supply from the
stream, an unknown portion of individuals can bypass the structure,
likely providing enough population interaction (as shown in other
species: Hanson 2001, p. 331; Gale et al. 2008, p. 1546). For example,
because the documented entrainment in the Smiths Fork drainage is
downstream of both populations, individuals from the Dry Fork Smiths
Fork population could reach the Muddy Creek population without
encountering the entraining structure.
In summary, while the potential impact of entrainment occurs across
the species' range (anywhere an unscreened diversion exists), it has
been documented downstream of only four populations, all in the Bear
River subregion. While the loss of emigrating individuals is important
to adequate species metapopulation dynamics, entrainment likely affects
only a small fraction of migrating individuals and does not impact
resident individuals in the core population areas. Entrainment may
reduce the ability of northern leatherside chub to migrate between
populations, but without an irrigation structure diverting the entire
stream, some individuals should be able to bypass structures. We found
no information that entrainment may act on this species to the point
that the species itself may be at risk, nor is it likely to become so.
Summary of Water Development
We determined that current levels of water development--entrainment
and dewatering--impact only a small portion of the extant populations
of northern leatherside chub, and primarily occur downstream of the
inhabited population areas. Because these factors are not occurring
near the existing core areas, they are largely impacting migrating
individuals and reducing population connectivity, not imperiling
overall population persistence. Future water development is closed in
Utah and Idaho, unlikely in Nevada, and small-scale in Wyoming. We
found no information that water development may act on this species to
the point that the species itself may be at risk, nor is it likely to
become so.
Water Quality
Water pollution and habitat degradation impair the ability of
aquatic systems to support life for at least 34 percent of the river
and stream habitats in the United States (Environmental Protection
Agency (EPA) 2002, p. 12). Examples of pollutants of concern for
aquatic systems include heavy metals, biocides, endocrine disrupters,
acid rain, sediments, dissolved solids, and excess nutrients (Stoddard
et al. 2005, p. 8; Helfman 2007, p. 158). The effects of pollution on
fish can include immediate death or long-term disabilities, such as
increased incidence of disease, abnormalities, and altered behavioral
or metabolic responses (Helfman 2007, p. 160).
Waters that do not meet water-quality standards due to point and
non-point sources of pollution are listed on the EPA's 303(d) list of
impaired water bodies. Therefore, we used the EPA 303(d) list of
impaired waters (see discussion under Factor D) to assist in
determining if pollution or degraded water quality is a threat to
northern leatherside chub (EPA 2010, pp. 1-2). Because the EPA's water
quality standards are thought to be protective of aquatic life, we
determined that a stream not listed as impaired on the EPA 303(d) list
did not have a high enough magnitude of pollution impacts to warrant
further analysis. States must submit to the EPA a 303(d) list (water-
quality-limited waters) and a 305(b) report (status of the State's
waters) every 2 years, making our analysis up-to-date. Of the 14
northern leatherside populations, 2 populations that occur in the Goose
Creek subbasin (Trapper and Beaverdam Creeks) are found in streams
listed in Idaho's most recent 2008 integrated 303(d)/305(b) report.
Trapper Creek's water quality is listed as impaired from nutrients
(defined by Idaho as including phosphorus, nitrogen, and organic
compounds), specifically total phosphorous, sediment, and dissolved
oxygen (IDEQ 2010, p. vii). Beaverdam Creek is impaired by nutrients
(total phosphorous), bacteria, temperature, sediment, and dissolved
oxygen (Lay 2003, p. xxii). Impaired water-quality conditions in both
creeks may be the result of livestock grazing effects (Lay 2003, pp.
69-70, 125).
These impairments can have varying impacts to fish and stream
habitats, although we have no information on how these impacted water-
quality parameters potentially affect northern leatherside chub.
Phosphorus is typically in limited supply in aquatic systems and,
therefore, excess phosphorus is considered a nutrient pollutant. Excess
phosphorus can cause eutrophication, which often results in harmful
algal blooms. These algal blooms, in turn, lead to depleted oxygen
conditions as they decay (Helfman 2007, p. 176). The State of Idaho
adopted guidelines from EPA that monthly averages of total phosphorus
should not exceed 0.05 milligram per liter (mg/L) in streams that enter
a lake or reservoir and 0.1 mg/L in any stream or other flowing water
to avoid eutrophication (IDEQ 2010, p.1).
Trapper Creek, a stream that enters Oakley Reservoir, is currently
listed on Idaho's 303(d) list for phosphorous and sediment (Lay 2003,
p. 45). Although total phosphorus levels exceeded guidelines in Trapper
Creek in almost all sampling events, there was little evidence of
eutrophication (nuisance algae growth) (Lay 2003, p. 68). Beaverdam
Creek exceeded the 0.1 mg/L total phosphorus limit in 16 out of 41
sampling events (39 percent) in 2001 (Lay 2003, p. 45). Although no
eutrophication has been seen, these results suggest that eutrophic
conditions could affect aquatic habitats in the future.
Fish need adequate dissolved oxygen in the water to breath. At
extremely low oxygen levels, fish suffocation is possible; however, it
is very uncommon, as fish have evolved a number of mechanisms to escape
this fate (Kramer 1987, p. 81). More common nonlethal

[[Page 63457]]

effects of reduced dissolved oxygen include reduced growth rates and
greater susceptibility to bird predators (fish approach water surface
for higher oxygen water and are more easily identified by birds)
(Kramer 1987, p. 82). Idaho established a dissolved oxygen minimum
concentration of 6 mg/L (Lay 2003, p. 48). This limit considers
salmonid spawning requirements (Lay 2003, p. 48) and is likely adequate
for northern leatherside chub. Dissolved oxygen levels are not
specifically considered to be impaired for Trapper Creek (IDEQ 2010, p.
vii) and are likely sufficient to fully support aquatic life, including
the northern leatherside chub. It is likely that northern leatherside
chub can persist in periodic, short-term, low dissolved oxygen
situations because they have been documented to persist in isolated
pool environments even after other species have perished (Belk and
Johnson 2007, pp. 70-71). It is unclear how they would respond to low
dissolved oxygen in the long term, as dissolved oxygen is a key
attribute for fish health. However, unless conditions were severe, we
would expect any low dissolved oxygen events to be short-term in
nature.
Sediment in the water column, also called Total Suspended Solids
(TSS), affects fish by reducing feeding abilities (rate and success),
degrading habitat (filling interstitial substrate space), and removing
oxygen (Newcombe and Jensen 1996, pp. 694-695). Sediment pollution can
come from various sources, including, but not limited to, grazing,
mining, and dirt roads. Hatchery experiments showed that northern
leatherside chub prefer cobble substrates with adequate interstitial
space for egg deposition (Billman et al. 2008a, p. 278), and field
research determined that northern leatherside chub feed on insects in
both the water column and the stream substrate (Bell and Belk 2004, p.
414). High sediment loads could interfere with the natural ecology
(e.g., feeding and reproduction) of the northern leatherside chub
through sedimentation of spawning and feeding habitats.
Correspondingly, microhabitat analysis does indicate that sand-silt
substrate is negatively associated with leatherside chub presence and
leatherside chub are more abundant at locations with gravel substrate
(Wilson and Belk 2001, p. 40). However, this analysis did not include
any of the large populations now known to inhabit degraded areas, such
as Muddy and Upper Twin Creeks, and included only one population now
known as northern leatherside chub (Trapper Creek, which is impacted by
other ecological factors as well as sediment pollution; the other
populations analyzed were southern leatherside chub) (Wilson and Belk
2001, p. 38). Because many of the populations of northern leatherside
chub persist in degraded areas and no data exist to clearly link
sediment with negative impacts, we conclude that sediment alone is not
a threat to northern leatherside chub. However, sediment may act in
conjunction with other impacts to threaten populations.
Limits of 25 mg/L TSS will provide a high level of protection for
aquatic organisms and 400 mg/L TSS will provide low protection (Lay
2003, p. 47). Idaho uses a monthly average of 50 mg/L TSS and a daily
maximum of 80 mg/L TSS as the upper limits for sediment (Lay 2003, p.
47). Both Trapper Creek and Beaverdam Creek exceeded daily maximum and
monthly average limits for TSS in 2001. Sediment levels in Trapper
Creek are highest following runoff events in the spring (March-May)
(IDEQ 2010, p. 6), and appear to negatively affect salmonids in the
lower sections of Trapper Creek (Lay 2003, p. 68). One event, from
September 2001, documented a monthly average of 1,649 mg/L TSS in
Beaverdam Creek, which is about 33 times the established Idaho
threshold (Lay 2003, p. 102). Elevated TSS conditions such as this may
cause low reproductive or feeding success by filling in substrate used
for both egg deposition and macroinvertebrate habitat and reducing
visibility for northern leatherside chub.
Thermal pollution (unnatural water temperatures) can affect fish by
altering metabolism and stressing biological norms. Thermal limits are
unique for each fish species. Idaho has established an upper
temperature standard of 22 [deg]C (72 [deg]F) for an instantaneous
limit and 19 [deg]C (66 [deg]F) as a daily average for cold water biota
(IDEQ 2010, p. 11). We determined that these temperature thresholds are
adequately conservative for northern leatherside chub (Lay 2003, pp.
38-39). Northern leatherside chub can tolerate higher stream
temperatures than salmonids, are documented to persist in streams as
high as 23 [deg]C (73 [deg]F) (Isaak and Hubert 2001, p. 27), and have
an upper incipient lethal temperature of 26 to 30 [deg]C (79 to 86
[deg]F) (as temperatures are increased in a tank, this is the
temperature at which 50 percent die) (Billman et al. 2008b, pp. 463,
468-469). Beaverdam Creek has reached daily averages of 19.32 [deg]C
(66.78 [deg]F) and 21.75 [deg]C (71.15 [deg]F), although we do not
consider these temperatures to be outside the thermal tolerance range
for northern leatherside chub.
Water-quality issues have been documented in Beaverdam and Trapper
Creeks within the Goose Creek subbasin, although aquatic communities in
each of these creeks still persist. For example, macroinvertebrate
communities in Trapper Creek and the upper portions of Beaverdam Creek
were considered healthy, and the fish community included species
believed to tolerate moderately impaired water quality (Lay 2003, pp.
99-100). However, the macroinvertebrate community in lower Beaverdam
Creek was indicative of poor water quality. Although Trapper Creek does
not harbor native trout normally associated with cool water systems
(Lay 2003, pp. 67, 68), Trapper Creek has been shown to support the
designated beneficial uses of cold-water biota and salmonid spawning
(IDEQ 2010, p. 9).
In summary, impaired water quality (based on 303(d) lists from the
various States) affects the habitat of two populations of northern
leatherside chub rangewide (Beaverdam and Trapper Creeks), both in the
Idaho portion of the Goose Creek subbasin (Snake River subregion),
although we know of no specific information on how impaired water
quality may affect the species. Levels of total phosphorus and
suspended sediment have been elevated in these streams and resulted in
correspondingly low dissolved oxygen levels. Because research cited
above demonstrates that elevated sediment, elevated phosphorus, and
reduced dissolved oxygen affect fish life-history traits, such as
reducing reproductive success (from clogged interstitial space),
decreasing feeding success (through impacts to macroinvertebrates), or
restricting growth (from low dissolved oxygen levels), it is possible
that these conditions have depressed population abundance in these
streams.
Only 2 of 14 populations occur in water-quality-impaired streams
and these streams are not known to be lethal to aquatic biota. We found
no information that water quality may act on this species to the point
that the species itself may be at risk, nor is it likely to become so.
Fragmentation and Isolation of Existing Populations
The arrangement, or interconnected nature, of species occurrences
is especially important when assessing species vulnerability, because
numerous studies link habitat fragmentation to population declines and
increased extinction risk (Dunham et al. 1997, p. 1126; Fagan et al.
2002, p. 3250; Fagan et al. 2005, p. 34 and references therein).

[[Page 63458]]

Human modifications to stream systems in the western United States,
such as reservoir creation, nonnative fish introductions, and
irrigation practices, fragment native fish distributions (Dunham et al.
1997, p. 1128; Hilderbrand and Kershner 2000, p. 513), including those
of the northern leatherside chub (UDWR 2009, pp. 5, 31). In the western
United States, physical barriers to dispersal (i.e., dams or culverts)
and unsuitable habitat (i.e., lakes, dewatered stretches, or areas with
increased predator abundance) are the most common agents of stream
fragmentation (Fagan et al. 2002, p. 3255).
Fragmentation of stream systems is unique, because unlike
terrestrial organisms, fish species are limited to movement through the
stream corridor and cannot simply move around an obstruction such as a
dam (Neraas and Spruell 2001, p. 1153; Fagan 2002, p. 3243). Because
stream fragmentation is often caused by impassable barriers, such as
dams or lakes, fish populations become isolated. Whether it is the
result of human alterations or natural patchiness in habitat, isolation
of local populations increases the risk of extirpation events because
immigration and recolonization events, ``rescue effects,'' are
precluded (Stacey and Taper 1992, p. 26; Dunham et al. 1997, p. 1131;
Fagan et al. 2002, p. 3250). When new individuals are unable to enter
into an area to supplement declining populations or to re-establish a
population after a catastrophic extirpation event, it is much more
likely the population will disappear permanently. It has been
demonstrated that the overall number of occurrences of a species is
less important to extinction risk than the fragmentation of occurrences
when other variables remain constant (abundance, etc.), with species
having a few clustered, interacting populations being less vulnerable
to extinction than a species with many, isolated populations (Fagan et
al. 2002, p. 3254).
It is important to consider the species' mobility and colonization
ability when fragmentation is discussed. For many freshwater fish
species, most individual fish do not emigrate from their resident home
area, but those that do tend to move great distances (Fagan et al.
2002, p. 3255). These long-distance dispersers are likely the primary
mechanism for the quick recolonization of extirpated stream reaches
(Peterson and Bayley 1993, p. 199). We know that the surrogate species
southern leatherside chub follows this pattern, with many individuals
having high site fidelity, but a small cohort (not dependent on
individual size) moving long distances for a small minnow species (0.5
to 2 km (0.3 to 1.25 mi)) over short time spans (within 1 year)
(Rasmussen 2010, pp. 42, 48-49). Based on similar physical capabilities
and life histories, it is likely that northern leatherside chub can
move similar distances. This ability to move provides a mechanism for
individuals to leave unsuitable habitat when conditions warrant and to
emigrate to new areas for natural demographic reasons.
We conclude that when suitable migratory corridors exist, northern
leatherside chub will successfully use them. Supporting this
conclusion, the collection of individual northern leatherside chub
throughout habitats downstream of known populations may indicate that
either yet undocumented populations exist or individuals are migrating
into new habitats. Regardless of the distinction, the collection of
individual northern leatherside chub found large distances away from
known populations, as defined in this finding, supports the conclusion
that northern leatherside chub can move large distances when suitable
pathways exist. For example, collections of individuals in lower
Sulphur Creek and the mainstem Bear River are between 17 and 29 km
(10.5 and 18 mi) downstream of the Yellow Creek population and between
11 and 19 km (7 and 12 mi) from the Upper Mill/Deadman Creeks
population (approximate distances) (McAbee 2011, p. 6). The occurrence
of individuals many kilometers downstream in the large inter-population
corridor (whether they be resident or emigrants) supports a conclusion
that these two populations could potentially interact because
individual presence demonstrates a suitable, occupied pathway exists
and is being used. Additionally, individuals collected downstream of
the Rock Creek population were between 8 and 13 km (5 and 8 mi) away
from the population center (Colyer and Dahle 2010, p. 5), which is a
distance similar to that separating the Rock Creek and Upper Twin Creek
populations. Similarly, individuals entrained in irrigation canals were
8 km (5 mi) downstream of the Muddy Creek population (Roberts and Rahel
2008, p. 951). Finally, individuals collected in mainstem Goose Creek
were between 6 and 18 km (4 and 11 mi) downstream of the Beaverdam
Creek population, which is distance similar to that separating the
Trout Creek population from Beaverdam (in the opposite direction).
Therefore, based on our knowledge of the northern leatherside chub's
movement ability and based on the occurrence of individuals many
kilometers downstream of extant populations, we conclude that
populations separated by moderate-distance (up to about 48 km (30 mi)),
barrier-free corridors are able to interact (Table 6).

Table 6--Summary of Fragmentation for Extant Northern Leatherside Chub Populations
--------------------------------------------------------------------------------------------------------------------------------------------------------
NATIONAL HYDROGRAPHY DATASET LOCATIONS
------------------------------------------------------ Population name State Connected to Multiple Occurrences within
Subregion Subbasin another population occurrences population
--------------------------------------------------------------------------------------------------------------------------------------------------------
Bear River...................... Upper Bear......... Upper Mill/Deadman UT/WY Yes............... Yes............... Throughout Mill Creek
Creeks. (UT & WY); Deadman
Creek.
Upper Sulphur/La WY No................ Yes............... Upper Sulphur Creek; La
Chapelle Creeks. Chapelle Creek.
Yellow Creek....... UT/WY Yes............... Yes............... Throughout Yellow Creek
(UT & WY); Thief
Creek.
Upper Twin Creek... WY Yes............... Yes............... Clear Creek; North Fork
Twin Creek.
Rock Creek......... WY Yes............... No................ Rock Creek.
-----------------------------------------------------------------------------------------------------------------------
Central Bear....... Dry Fork Smiths WY No................ No................ Dry Fork Smiths Fork.
Fork.
Muddy Creek........ WY Yes............... Yes............... Muddy Creek; Mill
Creek.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Snake River..................... Snake Headwaters... Pacific Creek...... WY No................ No................ Pacific Creek.
Salt River......... Jackknife Creek.... ID No................ Yes............... Jackknife Creek; Squaw
Creek; Trail Creek.
-----------------------------------------------------------------------------------------------------------------------

[[Page 63459]]

Goose Creek........ Trapper Creek...... ID No................ No................ Trapper Creek.
Beaverdam Creek.... ID Yes............... No................ Beaverdam Creek.
Trout Creek........ NV/ID Yes............... No................ Trout Creek.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Green River..................... Upper Green River/ North Fork Slate WY No................ Yes............... North Fork Slate Creek;
Slate Creek. Creek. Slate Creek.
Blacks Fork........ Upper Hams Fork.... WY No................ Yes............... Upper Hams Fork; West
Fork Hams Fork.
--------------------------------------------------------------------------------------------------------------------------------------------------------

When analyzing the potential threat of fragmentation of northern
leatherside chub, we considered two patterns of isolation. First, we
assessed the distribution of populations (defined in this finding as an
individual or set of 12-digit HUC(s)) across the species' range. For
example, we can say that the Jackknife and Pacific Creek populations
are isolated from other populations over the range, but the Upper Twin
Creek and Rock Creek populations can interact with each other (Table
6). Second, we assessed the occurrences of individuals within the
population boundaries, or, more simply stated, how widespread
individuals are within the population boundary. For example, we can say
that the Pacific and Rock Creek populations have one local occurrence,
but that the Jackknife and Upper Twin Creek populations have multiple
occurrences within one population boundary (Table 6). In other words,
the Jackknife Creek population has a more continuous distribution
within the subwatershed, while the Pacific Creek population is isolated
to one area.
This two-tiered approach lets us determine the overall extirpation
(localized extinction) risk to populations because catastrophic events
can range in scale from the entire population area to smaller areas
within the population. In the above population isolation example
(Jackknife and Pacific Creeks vs. Upper Twin and Rock Creeks), there
are no nearby populations to recolonize the Jackknife or Pacific Creek
populations if all individuals died from a large-scale disturbance.
However, if all individuals in the Rock Creek population died,
downstream emigrants from the Upper Twin Creek population could
recolonize the area. In the second example, if a catastrophic event
affected only part of the Jackknife Creek population (such as the Squaw
Creek tributary) and all individuals died, the area could be
recolonized by another occurrence (such as the Trail Creek tributary).
However, if a catastrophic event affected the single occurrence in
Pacific Creek and killed all individuals, the entire population would
be extirpated.
For this finding, we classified each population as either isolated
or not isolated based on known barriers preventing movement into the
population (reservoirs, culverts (Aedo et al. 2009, p. 1), or
impassable stream distances) (Table 6). If a population could interact
with at least one other population, we considered it not isolated.
Also, we focused only on permanent barriers, such as large reservoirs
or stream distances, instead of temporary barriers, because we assumed
permanent barriers will never be bypassed, but temporary barriers could
be bypassed at a low frequency with proper conditions. For example,
dewatered stretches were not considered a large scale barrier, because
in wetter years and wetter seasons they may carry enough water for
bypass. Conditions for recolonization or immigration need to occur only
sporadically to repopulate areas devoid of fish. Finally, we focused on
barriers affecting dispersal only into the population, because we are
primarily concerned with recolonization of extirpated areas.
Large reservoirs isolate three populations of northern leatherside
chub: Trapper and Jackknife Creeks in the Snake River subregion; and
Upper Sulphur/La Chapelle Creeks in the Bear River subregion. Large
stream distances isolated three additional populations from all other
populations: Pacific Creek in the Snake River subregion; and North Fork
Slate Creek and Upper Hams Fork in the Green River subregion.
Impassable culverts isolated one more population: Dry Fork Smiths Fork
in the Bear River subregion (Trout Unlimited 2010a, p. 7-8). The other
seven populations were considered connected to at least one other
population. Populations connect primarily in pairs: Muddy Creek and Dry
Fork Smiths Fork (Dry Fork Smiths Fork is isolated from Muddy Creek,
but not vice versa because culverts are impassable only in the upstream
direction); Yellow and Upper Mill/Deadman Creeks; and Rock and Upper
Twin Creeks in the Bear River subregion; and Beaverdam and Trout Creeks
in the Snake River subregion. These results are summarized in Table 6.
We next determined if each population contained multiple
occurrences within the population boundary. We considered a population
to have multiple occurrences if multiple tributaries were occupied or
northern leatherside chub were in divergent areas of the same stream
(separated by at least 10 km (6 mi) of approximate stream distance). Of
the 14 northern leatherside chub populations, 3 (Pacific and Trapper
Creeks in the Snake River subregion, and Dry Fork Smiths Fork in the
Bear River subregion) are isolated and likely contain only one
occurrence, making them vulnerable to a large-scale disturbance or
stochastic event.
The Trapper Creek population occurs in an upstream tributary to
Oakley Reservoir. Oakley Reservoir, and other reservoirs, act as
``environmental filters,'' preventing movement of small-bodied fish
between tributaries and fragmenting distributions (Matthews and Marsh-
Matthews 2007, p. 1042). Given the difference in stream and lake
habitats, and the presence of large-bodied predators in most
reservoirs, we believe it is unlikely that northern leatherside chub
could survive migrating through Oakley Reservoir because it supports
large populations of piscivorous (fish-eating) rainbow trout
(Oncorhynchus mykiss) and walleye (Sander vitreus) (IDFG 2010a, p. 2;
2010b, p. 3). We are not aware of other northern leatherside chub
populations that are located in direct tributaries to a reservoir.
Within the Bear River subregion, culverts surrounding the Dry Fork
Smiths Fork population likely prevent any immigration of northern
leatherside chub into the population, but do not prevent emigration of
individuals out of the population, as the barriers primarily prevent
upstream movement. However, the large population size upstream of

[[Page 63460]]

these culverts indicates that these barriers have not caused a
quantifiable impact to population size. In fact, these barriers may be
preventing downstream nonnative trout from entering the area, thus
protecting the population. Alternatively, these barriers may be causing
genetic isolation that could negatively impact the population.
Rangewide, 7 of the 14 northern leatherside chub populations are
isolated, which increases risk to large-scale disturbances or
stochastic events, such as extreme drought, large wildfire, or invasion
of nonnative species (Table 6). Four of the seven have multiple
occurrences within the population, offering the potential for rescue
effect dynamics. In fact, this situation may have recently played out
in the Jackknife Creek population, where a wildfire in 1991 burned a
significant portion of the sub-watershed, but did not affect upstream
portions of Squaw Creek (Isaak and Hubert 2001, pp. 26-27). It is
possible that northern leatherside chub either retreated to suitable
habitat within Squaw Creek during and after the fire, or that emigrants
from Squaw Creek recolonized other portions of Jackknife Creek.
In summary, isolation and fragmentation of northern leatherside
chub populations in stream systems can substantially reduce
recolonization potential, and increase the risk of a local extirpation
event due to a large-scale disturbance or stochastic event (Fagan et
al. 2002, p. 3255). When migratory pathways exist, fish species tend to
quickly recolonize a stream (Peterson and Bayley 1993, p. 199).
However, in desert systems, human modifications have reduced
opportunities for recolonization, eliminating the natural
counterbalance against extirpation (Fagan et al. 2002, p. 3255).
Populations able to interact, such as closely distributed populations,
are more likely to persist because clustered occurrences increase the
probability of recolonization (Fagan et al. 2002, p. 3255).
Two fragmented populations of northern leatherside chub, Trapper
and Pacific Creeks in the upper Snake River subregion, are isolated
from other populations and are vulnerable to stochastic events,
including local disturbances, such as disease, pollution, or floods.
Conversely, we believe the isolated Dry Fork Smiths Fork population is
not as vulnerable to a stochastic event due to its relatively large
population and its isolation (due to culverts surrounding the
population), which is precluding the migration of the predatory
nonnative brown trout into its habitats. Other isolated populations are
not impacted by fragmentation (Upper Sulphur/La Chapelle Creek; North
Fork Slate Creek; Upper Hams Fork), but their isolation puts them at an
increased risk from other large-scale threats and stochastic events. We
found no information that fragmentation may act on this species to the
point that the species itself may be at risk, nor is it likely to
become so.
Summary of Factor A
We found no information that livestock grazing, oil and gas
development, mining, water development, water quality, or fragmentation
of populations may act on this species to the point that the species
itself may be at risk, nor is it likely to become so. While these
factors individually have been shown to affect one or a few extant
populations of northern leatherside chub, none is considered a
significant threat to the species' persistence. For example, stable,
reproducing northern leatherside chub populations occur at many
locations where degraded habitat conditions exist. While these habitat
characteristics may not be optimal for northern leatherside chub
populations, their continued persistence and successful reproduction
demonstrate that they have some level of tolerance for less than
optimal environmental conditions. Because of the sufficient number of
populations, the interaction between several population locations, and
the large size of many populations, we conclude that local extirpation
risk to a small number of populations does not constitute a substantial
threat to the species. The best scientific and commercial information
available indicates that rangewide the northern leatherside chub is not
threatened by the present or future destruction, modification, or
curtailment of its habitat or range, nor is it likely to become so.

Factor B. Overutilization for Commercial, Recreational, Scientific, or
Educational Purposes

Commercial, recreational, scientific, and educational utilizations
are not common northern leatherside chub-related activities, and
protections are in place to limit their effect on the species. The use
of live baitfish, including northern leatherside chub, is not permitted
in the species' range (Harja 2009, p. 4; Miller et al. 2009, p. 3; UDWR
2009, p. 32). In addition, we are aware of no evidence that northern
leatherside chub are being illegally collected for any purposes.
Across the northern leatherside chub's range, permits are required
to collect the species for any reason. Individuals have been collected
for genetic analysis from various populations across the species' range
(Northern Leatherside Chub Conservation Team 2011, p. 4). These
collections were permitted under each State's regulatory authority (see
below), and because they are a small portion of the local population,
should not negatively impact local population persistence.
Northern leatherside chub are considered a ``prohibited'' species
under Utah's Collection, Importation, and Possession of Zoological
Animals Rule (R-657-3-1), which makes it unlawful to collect, import,
or possess northern leatherside chub without a permit (Harja 2009, p.
4). Use of the species for scientific or educational purposes also is
controlled by the UDWR, and the agency reviews requests to make sure
that no negative population impacts will occur (Harja 2009, p. 4).
Recently, northern leatherside chub were collected for a hatchery
population housed in Logan, Utah (Billman et al. 2008a, p. 274), and
future collections will be required for this population to persist
(Northern Leatherside Chub Conservation Team 2010, p. 5). However, the
number of northern leatherside chub taken for scientific and
educational purposes is low (UDWR 2009, p. 32).
The species is considered ``protected non-game'' under Idaho's
Rules Governing Classification and Protection of Wildlife (IDAPA
13.01.06), which makes it unlawful to take or possess northern
leatherside chub except with a permit under Rules Governing the
Importation, Possession, Release, Sale, or Salvage of Wildlife (IDAPA
13.01.10) (Schriever 2009, p. 1). In Wyoming, a rigorous collection
permitting system restricts commercial, scientific, and educational
activities (Miller et al. 2009, p. 3). Small-scale permits are given to
local residents to seine the Bear River drainage for baitfish (dead),
but these few permits are not impacting populations of northern
leatherside chub (Miller et al. 2009, p. 4). Northern leatherside chub
is not a protected species in Nevada. However, the Nevada Department of
Wildlife (NDOW) regulates collections of northern leatherside chub
through a permitting process (Johnson 2011a, pers. comm.).
Summary of Factor B
Northern leatherside chub are not overutilized for commercial,
recreational, scientific, or educational purposes. A limited number of
northern

[[Page 63461]]

leatherside chub are collected from wild populations for hatchery
augmentation or scientific investigation purposes, but the level of
collection is very small. The best scientific and commercial
information available indicates that the northern leatherside chub is
not threatened by overutilization for commercial, recreational,
scientific, or educational purposes, nor is it likely to become so.

Factor C. Disease or Predation

Disease and Parasitism
Disease and parasitism do not affect northern leatherside chub to a
significant degree. It is likely that the species encounters natural
diseases and parasites. However, we are not aware of any extant, wild
population that was substantially impacted by a disease or parasite; no
research project or collection effort has documented a disease or
parasite problem.
There is no discussion of disease or parasites in the threats
section of the Rangewide Conservation Agreement and Strategy for
Northern Leatherside Chub (described in detail under Factor D below)
(UDWR 2009, p. 32). However, one of the conservation elements in the
Conservation Agreement and Strategy is `Disease Management,' the goal
of which is to determine the extent of infections, monitor any known
infections, and prevent further infections by implementing biosecurity
protocols (UDWR 2009, p. 37). An example of disease management already
occurred in Utah, where UDWR raised a broodstock of wild northern
leatherside chub and used progeny to repatriate (reintroduce a
population) multiple sites (McKay et al. 2010, p. 1-3). Fishes brought
into the hatchery setting were treated for internal and external
parasites (Billman et al. 2008a, p. 274), ensuring that all restocked
and progeny fish are pathogen-free (Harja 2009, p. 4). The UDWR also
minimizes within-hatchery diseases, as demonstrated by their efforts to
disinfect eggs for maximum survival (FES 2010, pp. 25, 26).
There are no known disease or parasite problems for the northern
leatherside chub. We found no information that disease or parasites may
act on this species to the point that the species itself may be at
risk, nor is it likely to become so.
Predation
Northern leatherside chub are small minnows, and as such, are prey
for larger fish and sometimes birds (Sigler and Sigler 1996, pp. 77-
78). Historically, the main piscivorous (fish-eating) predator in
northern leatherside chub habitats was cutthroat trout--Bonneville
cutthroat trout (Oncorhynchus clarkii utah) in the Bear River
subregion, and Yellowstone cutthroat trout (Oncorhynchus clarkii
bouvieri) in the upper Snake River subregion (Greswell 1995, pp. 42-43;
May and Albeke 2005, p. 20; Nannini and Belk 2006, p. 458; May et al.
2007, p. 15). However, these subspecies likely exerted moderately weak
predation pressure on northern leatherside chub over much of their
evolutionary history because cutthroat trout only become primarily
piscivorous at larger sizes, when they tend to inhabit larger river
systems where northern leatherside chub are typically not found (Walser
et al. 1999, p. 276; Nannini and Belk 2006, pp. 458-459).
Weak predation pressure over evolutionary timescales often results
in species losing strong antipredator responses, which in fish species
includes escape (strong burst speeds) or concealment (effective
camouflage) (Nannini and Belk 2006, pp. 453, 460). In contrast, short
timescale adaptations to predation pressure include habitat shifts or
populations of lower carrying capacity. Meeting this expectation,
southern leatherside chub have slow and non-complex escape responses
(Nannini and Belk 2006, p. 460) and respond to intense predation by
shifting habitat usage (Walser et al. 1999, p. 272). Southern
leatherside chub may be more vulnerable to predation risks than other
native minnows because they lack effective predator responses, making
them a preferred prey (Nannini and Belk 2006, p. 460).
Because they share similar ecological niches, such as habitat
associations (Belk and Wesner 2010, p. 12) and native predators, we
expect that northern leatherside chub have predator responses similar
to southern leatherside chub and also are likely vulnerable to
predation. By losing effective antipredator responses, northern
leatherside chub were able to divert more energy to other life-history
characteristics, such as foraging, reproduction, and growth (Nannini
and Belk 2006, p. 460). This adaptation produces benefits under
natural, evolutionarily historical conditions where northern
leatherside chub primarily coexisted with other small-bodied fish and
cutthroat trout species, but places it at a disadvantage when
encountering highly predatory species.
One such predatory species is brown trout. Native to Europe and
western Asia, brown trout is an introduced predator that was widely
stocked throughout the United States for its value as a sportfish
(Sigler and Sigler 1996, p. 205; Stoddard et al. 2005, pp. 11-12).
Brown trout are highly predatory to the detriment of native fish
communities, often out-competing and preying on native predators, while
also consuming many small, native fish species (Garman and Nielsen
1982, p. 862; Behnke 1992, p. 54; Wang and White 1994, p. 475; Walser
et al. 1999, p. 272; Budy et al. 2005, pp. xii-xiii, 58-73). Brown
trout are now commonly distributed throughout adequate habitats in the
Bear and upper Snake River subregions and have affected native fish in
these areas. They have displaced native cutthroat species (Budy et al.
2005, p. xii), limiting cutthroat trout populations to mostly headwater
streams where temperatures are generally too cold for brown trout
survival. Therefore, it is likely that this introduced predator reduced
the historical range of northern leatherside chub.
The closely related southern leatherside chub has altered habitat
selection because of predation pressure by brown trout (Walser et al.
1999, p. 272). This outcome is not surprising, given that: (1)
Piscivory is a dominant factor shaping fish community structure in
stream ecosystems (Jackson et al. 2001, p. 157); (2) other prey species
retreat to safer periphery habitat when faced with predation risks
(Fraser et al. 1995, p. 1466); and (3) introduced populations of brown
trout have affected native species worldwide (McDowall 2003, pp. 230-
231). For example, in Diamond Fork Creek, Utah, southern leatherside
chub inhabited less suitable, lateral habitats (cutoff pools and
backwaters) when the main channel contained brown trout, despite the
presence of suitable main channel microhabitats (Walser et al. 1999, p.
272). Because unoccupied main channel habitats were identical to those
occupied in streams without brown trout, it is likely that southern
leatherside chub select poorer quality habitat to avoid brown trout
predation (Walser et al. 1999, p. 275). This hypothesis was confirmed
on a broad geographic scale. In areas where brown trout populations
overlapped with juvenile mountain sucker (Catostomus platyrhynchus) and
southern leatherside chub, the latter two species used backwaters and
cut-off pools almost exclusively, whereas in the absence of brown
trout, they commonly used main channel pools (Olsen and Belk 2005, pp.
501, 503). This suggests that predation is an important factor
affecting habitat use by small native fish, limiting them to areas of
less suitable habitat.
Although considered poorer habitats than the main channel, lateral
areas

[[Page 63462]]

likely offer native fish their only chance of persistence, because
brown trout will prey on individuals in main channel habitats.
Therefore, it is important to preserve lateral habitats where northern
leatherside chub and brown trout overlap, because even with brown trout
present, small native fish can survive with adequate habitat complexity
(Olsen and Belk 2005, p. 504). Side channel habitats are only available
in natural systems with adequate flow, not degraded or simplified
systems, such as de-watered or channelized streams (Olsen and Belk
2005, p. 504). In the event that refuge areas are not available, it is
not likely that northern leatherside chub populations can persist under
such heavy predation pressure.
Based on an analysis of brown trout and southern leatherside chub,
we expect that when refuge habitat is not available, brown trout
predation exerts direct mortality on northern leatherside chub. Stream
experiments revealed that southern leatherside chub are 16 times more
likely to survive if brown trout are absent than if present (Nannini
and Belk 2006, p. 458), which explains why lateral habitats are a safer
option. For example, in Diamond Fork Creek, southern leatherside chub
were absent in upstream areas without lateral habitats in 1999 (Walser
et al. 1999, p. 276). Later, when flows were permanently reduced
throughout Diamond Fork Creek by a water conveyance pipeline, lateral
habitats disappeared completely and southern leatherside chub were soon
extirpated from the entire system, presumably from brown trout
predation (Hepworth and Wiley 2007, pp. 3-4).
Although brown trout and northern leatherside chub can co-occur,
the presence of brown trout potentially impacts northern leatherside
population densities in 3 of 14 populations (Jackknife Creek, Dry Fork
Smiths Fork, and Muddy Creek). Brown trout were negatively correlated
with the probability of encountering southern leatherside chub over
many tributaries in the Sevier River drainage (Wilson and Belk 2001, p.
39). Areas with high densities of southern leatherside chub were always
free of brown trout, and areas where the two species overlapped had
consistent low densities of southern leatherside chub (Wilson and Belk
2001, p. 41). Low population densities are likely a result of
cumulative losses of individuals to predation, preventing populations
from reaching carrying capacity.
Even when brown trout do not inhabit the same location as northern
leatherside chub, brown trout can exert indirect pressure on the
species by acting as a migration barrier. Effective aquatic predators
can act as a dispersal barrier by killing prey (Fraser et al. 1995, pp.
1461, 1468). Therefore, the predation pressure on main channel habitats
(Walser et al. 1999, p. 272) may prevent northern leatherside chub from
moving between populations, exacerbating an already fragmented species
distribution. However, like resident fish, emigrants are more likely to
survive migrations when complex habitat (through adequate water supply)
is available (Gilliam and Fraser 2001, pp. 267, 270).
More broadly, predators can fragment an otherwise consolidated
distribution of prey species, forcing the prey to abandon otherwise
habitable areas for constricted peripheral locations (Fraser et al.
1995, p. 1461). In fact, it is possible that through past population
extirpations combined with current migration impediments, brown trout
are the cause of the current fragmentation of leatherside populations
(Wilson and Belk 2001, p. 41).
An analysis of the range contraction of northern leatherside chub
compared to brown trout stocking offers some insight into the
relationship between the two species (current fish stocking policies
are analyzed under Factor D). Between 1975 and 2005, the States of Utah
and Wyoming stocked at least 2.28 million brown trout in the Bear River
subregion (IDFG 2010c, entire; UDWR 2010, pp. 1-747; WGFD 2010, pp. 1-
10). Recent surveys indicate that no extant northern leatherside chub
populations are in close proximity to the stocking locations (Service
2011, pp. 33-34). While this could be simply an artifact of suitable
habitat or preferential stocking locations, we conclude that the
instances of historical extirpation combined with the ecological
influences described above suggest a more causative effect.
Further support of this causative effect is documented in Utah.
Between 1981 and 2005, approximately 400,000 brown trout were stocked
in the Little Bear/Logan subbasin (UDWR 2010, pp. 1-747), where
northern leatherside chub historically occurred but are no longer found
(UDWR 2009, p. 42). Surveys of historical northern leatherside chub
locations in the nearby Lower Bear subbasin also yielded no northern
leatherside chub, but did document large numbers of brown trout (UDWR
2009, p. 42). Although there are no voucher specimens of northern
leatherside chub for these historical locations, UDWR considers
collections in the Little Bear River (four preserved skeletons) as
reliable because of the reputation of the collector (W.F. Sigler)
(McKay 2011, pers. comm.). It is not unreasonable to conclude that high
densities of brown trout removed northern leatherside chub from these
locations.
Stocking of brown trout also occurred in subbasins with extant
northern leatherside chub. Near the Utah-Wyoming border, Utah and
Wyoming stocked around 250,000 brown trout in the mainstem Bear River
from 1980 to 1997, and Wyoming stocked around 500,000 in Woodruff
Reservoir from 1985 to 1997 (UDWR 2010, pp. 1-45; WGFD 2010, pp. 7-10).
These locations centralize an area of unoccupied habitat between the
two sets of populations in the Upper Bear subbasin. In the Salt River
subbasin, northern leatherside chub no longer occur in any tributaries
stocked with brown trout. Lastly, Wyoming stocked around 250,000 brown
trout in Sulphur Creek Reservoir, directly downstream of the Sulphur/
LaChapelle Creeks population before 2000 (WGFD 2010, pp. 3-6), possibly
isolating that population of northern leatherside chub completely.
Therefore, it is possible that past stocking events and subsequent
migration of brown trout shaped the current distribution of northern
leatherside chub and could prevent many populations from interacting in
the future.
Within the Snake River drainage, populations of northern
leatherside chub persist in at least two streams where brown trout were
historically stocked. In the Goose Creek subbasin, Nevada has not
stocked brown trout since 1950 (Johnson 2010, pers. comm.), nor has
Utah recently stocked any nonnative trout (Schaugaard and Thompson
2006, pp. 5-6). Idaho stocked about 5,500 brown trout in Trapper Creek
in 1988 (IDFG 2010c, p. 10), but they did not persist, as rainbow trout
are the only salmonid recently collected in the stream (Keeley 2010,
pp. 3-4). Leatherside chub and brown trout also were found together at
two sites in Jackknife Creek, but brown trout made up less than 6
percent of salmonid abundance at both sites (Univeristy of Wyoming
2010, pp. 1-4). In contrast, in the Twin Creek drainage, where a solely
native fish community resides, two northern leatherside chub
populations currently persist, with individuals in many tributaries
(Colyer and Dahle 2010, p. 5).
The presence of brown trout can cumulatively intensify abiotic
factors, such as reduced water level from drought or irrigation, or
increased stream temperature from climate change (see discussion under
Factor E). As was demonstrated in Diamond Fork Creek, reduced water
levels force native, small-

[[Page 63463]]

bodied fish from refuge habitat to main channel habitat, where brown
trout can easily prey on them. In fact, brown trout will prey on
southern leatherside chub preferentially over redside shiner (Nannini
and Belk 2006, p. 458). The relationship between water level and brown
trout presence also potentially impacts migration patterns. Water
levels do not affect prey fish movement in the absence of predators;
however, water levels are an issue when predators are present (Gilliam
and Fraser 2001, p. 270). In other words, when stream levels are low
from drought or human use, northern leatherside chub are predicted to
move freely if brown trout are absent, but will likely not move if
brown trout are present. Water level is rendered influential only when
a predator is present (Gilliam and Fraser 2001, p. 270).
Northern leatherside chub populations can endure if brown trout are
absent or at very low densities. However, based on the ecological
mechanisms described above and the lack of strong overlapping
distribution, we conclude that future introduction of brown trout into
streams with extant northern leatherside chubs, although not currently
anticipated, would likely impact those populations.
Other salmonid species, both native and nonnative, could impact
northern leatherside chub populations through predation as well.
Although not normally as piscivorous as brown trout, introduced rainbow
trout impact native fish communities worldwide (Lintermans 2000 in
Blinn et al. 1993, p. 139; McDowall 2003, p. 231; Vigliano et al. 2009,
p. 1406). In fact, rainbow trout likely influence habitat use,
behavior, and distribution of another Lepidomeda species, the Little
Colorado spinedace (L. vittata) (Blinn et al. 1993, pp. 141-142). The
Little Colorado spinedace is similar to northern leatherside chub, in
that it evolved without strong predation pressure but is now forced
into suboptimal habitats by an introduced predator (Blinn et al. 1993,
p. 142). We conclude that the introduction of rainbow trout also poses
a threat, albeit less than brown trout, because rainbow trout exert
similar nonnative predation pressure on northern leatherside chub.
Brook trout (Salvelinus fontinalis) are another nonnative trout
species occurring in the northern leatherside chub's range. While brook
trout are commonly referred to as carnivorous, voracious feeders, they
primarily feed on insects throughout their life but will eat fish when
possible (Sigler and Sigler 1996, p. 211). Amazingly, they are known to
eat amphibians, reptiles, and mammals on rare occasions, demonstrating
their variable diet (Sigler and Sigler 1996, p. 211). However, it is
important to note that even large brook trout are not especially
piscivorous (Sigler and Sigler 1996, p. 211), making them less of a
predatory threat than either brown or rainbow trout.
The most likely impact of brook trout on northern leatherside chub
is competition for available resources. Brook trout populations are
known to become locally overabundant to the point that the size class
of the population is stunted and resources are scarce (Sigler and
Sigler 1996, pp. 212-213). However, brook trout inhabit coldwater
habitats, such as cool, clear headwater streams and spring-fed streams
and lakes (Sigler and Sigler 1996, p. 212). They seek water
temperatures of 10 to 14.4 [deg]C (50 to 58 [deg]F), high-gradient
streams (3 to 6 percent), and gravel substrate (Sigler and Sigler 1996,
pp. 211-212; Nadolski 2008, p. 63). In contrast, northern leatherside
chub occupy streams with higher temperatures (15.6 to 20 [deg]C or 60
to 68 [deg]F) (Sigler and Sigler 1996, p. 79), prefer low stream
gradients (0.1 to 4 percent (Wilson and Belk 2001, p. 39)), and can
tolerate sediment-laden habitats (UDWR 2009, p. 27).
Based on available information, we conclude that brook trout pose a
very limited threat to northern leatherside chub even though brook
trout occur both upstream and concurrently with 6 of 14 northern
leatherside chub populations. Habitats that are occupied by northern
leatherside chub are likely suboptimal for brook trout. While
populations of the two species overlap, densities of brook trout are
generally low in these locations, while densities of northern
leatherside chub are generally stable and relatively high. We also
conclude that upstream populations of brook trout are not a threat
because many are characterized by abundant, small individuals that are
not piscivorous and inhabit areas unlikely to support northern
leatherside chub if they were removed (Nadolski 2008, pp. 78-79; WGFD
2009, p. 5). For example, at Deadman Creek, brook trout have seemingly
overpopulated the portions upstream of a dense northern leatherside
population (Nadolski 2008, p. 78). However, the brook trout population
is comprised of small, sedentary, non-piscivorous fish (Nadolski 2008,
p. 38; 2011 pers. comm.). We note that this is the only population
where brook trout stomach contents have been collected, and it would
improve our understanding of the species if more investigations studied
the interactions between brook trout and northern leatherside chub. As
discussed in more detail under Factor E (climate change), predation
impacts from brook trout are not expected to increase if climate change
predictions are accurate. Warming waters (either from increased air
temperatures or drought conditions) may benefit northern leatherside
chub and harm brook trout, as northern leatherside chub are more
tolerant and ecologically adapted to warmer water temperatures.
The presence of native cutthroat trout species poses a very limited
risk to northern leatherside chub persistence because cutthroat trout
are a natural predator that does not exert excessive predation
pressure. In fact, conservation actions that remove nonnative trout and
introduce native cutthroat will likely produce beneficial effects to
northern leatherside chub through reduced predation.
To fully assess the threat of nonnative trout, we assessed the
probability that nonnative trout could currently alter populations or
invade existing northern leatherside chub populations in the future.
Fish stocking policies have recently changed, resulting in a large
reduction of brown trout stocking in the area. An analysis of recent
collection data shows that nonnative trout populations are nearby 8 of
the 14 extant northern leatherside chub populations, although the
number is reduced to only 5 when brook trout (which are less
piscivorous) are excluded (Table 7).

TABLE 7--Presence of Nonnative Salmonids (brook, brown, and rainbow trout) and Native Cutthroat Trout at Extant
Northern Leatherside Chub Populations
----------------------------------------------------------------------------------------------------------------
National Hydrography Dataset Boundaries Presence of Salmonids
---------------------------------------------------- ----------------------------------------
Population Nonnative (brook,
Subregion Subbasin brown, or rainbow) Native cutthroat
----------------------------------------------------------------------------------------------------------------
Bear River..................... Upper Bear........ Upper Mill/Deadman Brook trout Yes.
Creeks. upstream.

[[Page 63464]]

Upper Sulphur/La No................ Yes.
Chapelle Creeks.
Yellow Creek...... No................ Yes.
Upper Twin Creek.. No................ Downstream.
Rock Creek........ No................ Yes.
Central Bear...... Dry Fork Smiths Brown & brook Downstream.
Fork. trout downstream.
Muddy Creek....... Brown & brook Downstream.
trout downstream.
Snake River.................... Snake Headwaters.. Pacific Creek..... Brook trout Yes.
present.
Salt River........ Jackknife Creek... Brown trout Yes.
downstream.
Goose Creek....... Trapper Creek..... Rainbow trout No.
present.
Beaverdam Creek... No................ No.
Trout Creek....... No................ Yes.
Green River.................... Upper Green River/ North Fork Slate Brook trout No.
Slate Creek. Creek. upstream.
Blacks Fork....... Upper Hams Fork... Rainbow present/ No.
Brook trout
upstream.
----------------------------------------------------------------------------------------------------------------

In the Bear River subregion, the only populations accessible by
nonnative trout are the Dry Fork Smiths Fork, Muddy Creek, and Upper
Mill/Deadman Creeks populations. Although the Muddy Creek and Dry Fork
Smiths Fork populations do not currently have nonnative trout in
occupied northern leatherside chub habitat, downstream tributaries in
the Smiths Fork drainage (not occupied by northern leatherside chub)
contain brown and brook trout (Roberts and Rahel 2008, p. 951; Trout
Unlimited 2010b, pp. 78-91, Table 6). Muddy Creek is accessible to
these downstream populations, because there is no barrier separating
the areas (Colyer and Dahle 2007, p. 8), but Dry Fork Smiths Fork is
isolated by impassable culverts (Trout Unlimited 2010a, pp. 7-8, 10-
12). However, the aquatic habitat in Muddy Creek is currently
unsuitable for brown trout, likely preventing their colonization of the
area. Brook trout are currently found upstream of occupied northern
leatherside habitat in Deadman Creek, but not in the rest of the system
(Nadolski and Thompson 2004, p. 3; Nadolski 2008, p. 78; Belk and
Wesner 2011, pp. 1-4).
Although Sulphur Creek Reservoir, downstream of the Upper Sulphur/
La Chapelle Creeks population, contains brown and rainbow trout, we
conclude they cannot access northern leatherside chub habitat. Prior to
2000, the WGFD stocked thousands of brown trout in Sulphur Creek
Reservoir (WGFD 2010, pp. 3-6), creating a possible source for
colonization into the Upper Sulphur/La Chapelle Creeks population.
However, no brown trout were collected in upstream reaches occupied by
northern leatherside (Belk and Wesner 2011, pp. 1-4). Brown trout have
not moved upstream likely because there are abundant food resources in
the reservoir and habitat directly upstream of the reservoir is
degraded by irrigation return flow (Amadio 2011, pers. comm.).
In the upper Snake River subregion, nonnative trout co-occur with
leatherside chub in two of the five populations and are downstream of
another population. Brown trout are found in lower reaches of Jackknife
Creek and were previously shown to co-occur with northern leatherside
chub (Isaak and Hubert 2001, pp. 6, 27), although more recently brown
trout were not found at occupied northern leatherside chub sites
(Keeley 2010, pp. 45-60). Although brook trout inhabit the same reach
of Pacific Creek occupied by northern leatherside chub, they generally
use different habitats (Grand Teton National Park 2009, p. 1).
Introduced rainbow trout are documented in Trapper Creek (Keeley 2010,
pp. 4-5), although information is lacking on what if any impact they
have on the northern leatherside chub population.
In the Green River subbasin, both northern leatherside chub
populations occur downstream of brook trout (WGFD 2009, pp. 1-5). In
addition, low densities of rainbow trout occur in the Upper Hams Fork,
but they are likely not reproducing (WGFD 2009, pp. 1-3).
Summary of Predation
Nonnative predators, especially brown trout, impact northern
leatherside chub populations. In the presence of brown trout,
leatherside chub occupy lateral habitats that could provide refuge
against predation (Walser et al. 1999, p. 272), likely reducing
reproductive and forage success. Brown trout hold leatherside chub
populations at low density (Wilson and Belk 2001, p. 41), likely
because leatherside chub are preferred prey (Nannini and Belk 2006, p.
458).
While the stocking of brown trout has been greatly reduced in
recent years in several streams within the range of northern
leatherside chub, established brown trout populations are likely
sustainable in many locations, as shown in the Salt River subbasin
(Isaak and Hubert 2001, p. 6). Currently, the distribution of brown and
rainbow trout overlaps with northern leatherside chub populations only
in a few locations (Trapper Creek, Upper Hams Fork, and the lowest
portion of Jackknife Creek). Any changes in current stream conditions
(i.e., changing water quality and temperatures) could facilitate
upstream distributional shifts for these nonnatives, putting northern
leatherside chub at increased risk of predation. For example, if the
projected changes in climate warms waters across the western United
States (EPA 2008, p. 8), brown trout could possibly move upstream into
currently occupied northern leatherside chub habitats; however, we have
no specific information to indicate that this is likely to happen.
In summary, we found no information that predation may act on this
species to the point that the species itself may be at risk, nor is it
likely to become so. Most populations (9 of 14) do not share habitats
with nonnative trout of concern, and 3 of 5 potentially impacted
populations occur where habitats are

[[Page 63465]]

likely not suitable for salmonids (i.e., Muddy Creek), contain
migration barriers in the form of impassable culverts (i.e., Dry Fork
Smiths Fork), or have only low densities of the nonnative rainbow trout
(i.e., Upper Hams Fork). Therefore only two northern leatherside chub
populations (in the Snake River subregion) may be vulnerable to the
effects of nonnative trout. However, we have no information to indicate
how the species and its habitats have been impacted. Brown trout occur
in the lower reaches of Jackknife Creek, primarily downstream of
northern leatherside chub populations in warmer waters (although they
have been found to co-occur in past samples). Rainbow trout continue to
co-occur with northern leatherside chub in Trapper Creek where the IDFG
continues to stock nonnative rainbow trout into Oakley Reservoir.
Because nonnative trout impact a small proportion of populations,
predation does not act on this species to the point that the species
itself may be at risk, nor is it likely to become so.
Summary of Factor C
At this time we know of no information that indicates that the
presence of parasites or disease significantly affects northern
leatherside chub, or is likely to do so. There is strong evidence that
northern leatherside chub can be impacted by predation from nonnative
trout, especially brown trout. Nonnative trout currently occur near or
downstream to 5 of 14 northern leatherside chub populations. While
these populations are more vulnerable to predation and other effects
from nonnative trout, we have no information that indicates nonnative
trout are currently impacting these populations or the species as a
whole. We found no information that disease or predation may act on
this species to the point that the species itself may be at risk, nor
is it likely to become so.

Factor D. The Inadequacy of Existing Regulatory Mechanisms

The Act requires us to examine the inadequacy of existing
regulatory mechanisms with respect to extant threats that place
northern leatherside chub in danger of becoming either endangered or
threatened. Regulatory mechanisms affecting the species fall into three
general categories: (1) Land management; (2) State mechanisms; and (3)
Federal mechanisms.
Land Management
Land ownership in the entire upland watershed affects aquatic
habitats because land activities distribute effects downslope into the
stream corridor. Subwatersheds harboring populations of northern
leatherside chub are distributed across BLM, private, State, USFS, and
National Park Service (NPS) lands and incur varying regulatory
mechanisms depending on land ownership (USFWS 2011, pp. 11-17). The
following section provides a brief description of how land ownership
affects regulatory mechanisms where extant northern leatherside chub
populations occur. We first analyze the land ownership of the entire
upland area to analyze general effects, and then analyze local riparian
corridor ownership to investigate more local effects.
Currently occupied northern leatherside chub streams are contained
in 14 populations based on subwatersheds (HUC12) covering approximately
242,864 hectares (938 square mi). Land ownership in occupied
subwatersheds is comprised of privately owned land (31.5 percent in the
States of Idaho, Nevada, Utah, and Wyoming), as well as lands managed
by BLM (30 percent), NPS (3.5 percent), USFS (30.5 percent), and the
States of Wyoming (4.3 percent) and Idaho (0.04 percent) (Service 2011,
pp. 11-17). Aside from the subwatersheds in the Upper Bear River
subbasin (Upper Mill/Deadman Creeks, Upper Sulphur/La Chapelle Creeks,
and Yellow Creek), which are almost entirely privately owned, most
northern leatherside chub subwatersheds are affected by upstream lands
that are managed by the BLM and the USFS, or the NPS for Pacific Creek
(Table 8). However, more than three-quarters of northern leatherside
chub subwatersheds have some, or their entire, occupied habitat on
private lands, which typically encompasses the wetted channel and the
riparian buffer surrounding the stream (Table 9).

Table 8--Land Ownership by Percent of Subwatersheds (12-Digit HUC) With Northern Leatherside Chub Populations
----------------------------------------------------------------------------------------------------------------
Upland watershed land ownership by entity (% land
owned)
Population name ------------------------------------------------------
BLM Private State USFS NPS
----------------------------------------------------------------------------------------------------------------
Bear River Subregion
----------------------------------------------------------------------------------------------------------------
Upper Mill/Deadman Creeks................................ 0 68 1 31 0
Upper Sulphur/La Chapelle Creeks......................... 6 88 6 0 0
Yellow Creek............................................. 1 95 4 0 0
Upper Twin Creek......................................... 77 14 6 0 3
Rock Creek............................................... 61 19 10 0 10
Dry Fork Smiths Fork..................................... 40 26 10 24 0
Muddy Creek.............................................. 63 19 18 0 0
------------------------------------------------------
Total................................................ 45 41 8 3 3
----------------------------------------------------------------------------------------------------------------
Snake River Subregion
----------------------------------------------------------------------------------------------------------------
Pacific Creek............................................ 0 4 0 48 48
Jackknife Creek.......................................... 1 5 0 94 0
Trapper Creek............................................ 12 5 1 82 0
Beaverdam Creek.......................................... 19 8 1 72 0
Trout Creek.............................................. 41 8 0 51 0
------------------------------------------------------
Total................................................ 9 5 <1 71 15
----------------------------------------------------------------------------------------------------------------

[[Page 63466]]

Green River Subregion
----------------------------------------------------------------------------------------------------------------
North Fork Slate Creek................................... 88 9 3 0 0
Upper Hams Fork.......................................... 12 13 2 73 0
------------------------------------------------------
Total................................................ 30 13 2 55 0
----------------------------------------------------------------------------------------------------------------

Table 9--Estimated Land Ownership in Miles for Occupied Habitat of Northern Leatherside Chub Populations
----------------------------------------------------------------------------------------------------------------
Land ownership of occupied habitat Approximate
------------------------------------------------------- river miles of
Population name BLM Private State USFS NPS occupied
(percent) (percent) (percent) (percent) (percent) habitat
----------------------------------------------------------------------------------------------------------------
Bear River Drainage
----------------------------------------------------------------------------------------------------------------
Upper Mill/Deadman Creeks................ 0 100 0 0 0 10
Upper Sulphur/La Chapelle Creeks......... 0 100 0 0 0 15
Yellow Creek............................. 2 96 2 0 0 27
Upper Twin Creek......................... 40 40 20 0 0 9
Rock Creek............................... 30 70 0 0 0 3
Dry Fork Smiths Fork..................... 65 35 0 0 0 3
Muddy Creek.............................. 5 0 95 0 0 5
----------------------------------------------------------------------------------------------------------------
Snake River Drainage
----------------------------------------------------------------------------------------------------------------
Pacific Creek............................ 0 0 0 0 100 2
Jackknife Creek.......................... 0 0 0 100 0 8
Trapper Creek............................ 15 60 0 25 0 8
Beaverdam Creek.......................... 20 50 0 30 0 3
Trout Creek.............................. 10 90 0 0 0 5
----------------------------------------------------------------------------------------------------------------
Green River Drainage
----------------------------------------------------------------------------------------------------------------
North Fork Slate Creek................... 80 20 0 0 0 9
Upper Hams Fork.......................... 10 15 15 60 0 10
----------------------------------------------------------------------
Total Estimated River Miles.......... ......... ......... ......... ......... ......... 117
----------------------------------------------------------------------------------------------------------------

Quantifying riparian habitat ownership for areas surrounding
occupied northern leatherside chub stream reaches required an internal
investigation. No published information is available regarding the
number of river-kilometers occupied by northern leatherside chub
populations; therefore, we calculated a basic estimate by using
presence and absence data supplied by various researchers and agencies.
Our estimate indicates that occupied river-kilometers for northern
leatherside chub are approximately 188 km (117 mi). This total includes
approximately 115 km (72 mi) on private land in Idaho, Nevada, Utah,
and Wyoming; 29 km (18 mi) on lands managed by the BLM; 14 km (9 mi) on
lands managed by the States of Wyoming and Idaho; and 3 km (2 mi) and
27 km (17 mi) on lands managed by the NPS and USFS, respectively (Table
9). Thus, a total of 61 percent of the estimated occupied northern
leatherside chub habitat in the 4-State area occurs on privately owned
land (Service 2011, pp. 11-17).
Subwatersheds with significant portions of federally owned land
allow for greater regulatory control over land management practices
(oil and gas development, grazing, water development, mining, etc.)
that have the potential to negatively affect northern leatherside chub
populations and their habitat. Federal agencies conduct land management
activities under various legislations (see Federal Mechanisms below)
that do not apply to private lands. On private lands, the Clean Water
Act (CWA; 33 U.S.C. 1251 et seq.) and State mechanisms (see below) are
the primary regulatory mechanisms that regulate land use activities.
State Mechanisms
Collection or Possession
Northern leatherside chub are considered ``prohibited'' species
under the Utah Collection Importation and Possession of Zoological
Animals Rule (R-657-3-1), making them unlawful to collect or possess
(UAC 2011, pp. 18-19). These species receive protection from
unauthorized collection and take. In Wyoming, the use of live baitfish
is prohibited throughout the range of northern leatherside chub and
very few live baitfish collection licenses are sold in the Bear River
drainage. Persons that have these permits collect baitfish on a small
scale for individual use (Miller et al. 2009, pp. 3-4) (see discussion
under Factor B). The State of Idaho has classified northern leatherside
chub as a ``Protected Nongame'' species, and State

[[Page 63467]]

regulations specify that no person shall take or possess such species
at any time or in any manner except as provided for in authorized
circumstances (Schriever 2009, p. 1). Northern leatherside chub are not
listed as a protected species in the State of Nevada; however, the use
of live baitfish is prohibited in the State within the species' range,
and the NDOW monitors collection of rare species by researchers (UDWR
2009, pp. 32-33). These policies are adequately protecting northern
leatherside chub from overutilization (see Factor B discussion) and are
not expected to change in the future.
Conservation and Protection
The States of Idaho, Wyoming, Nevada, and Utah provide protection
and conservation direction for northern leatherside chub under their
State comprehensive wildlife conservation strategies, which are
required by the Service for a State wildlife agency to receive State
wildlife grants. In addition, all States within the range of the
species are signatory to the ``Rangewide Conservation Agreement and
Strategy for Northern Leatherside''. The goals of this document are to
ensure the long-term persistence of the northern leatherside chub
within its historical range and to support the development of multi-
State conservation efforts through coordinated conservation actions and
regulatory consistency. The objectives of the document are to identify
and reduce threats to northern leatherside chub and its habitat,
determine the existing range of the species, maintain and monitor
existing self-sustaining populations and their habitat, restore
populations at selected localities within the historical range, augment
selected populations if necessary, maintain genetic diversity, and
pursue additional research questions (UDWR 2009, p. 1). Other
signatories to the document include the Service, BLM, NPS, Bureau of
Reclamation, USFS, Trout Unlimited, and The Nature Conservancy (UDWR
2009, pp. 2-3). While we do not rely on these strategies for our
finding, they are extremely valuable because they help prioritize
conservation actions within each State and form partnerships across the
species' range (UDWR 2009, entire). These policies are not expected to
change in the future.
Fish Stocking
The UDWR follows their Policy for Fish Stocking and Transfer
Procedures, and no longer stocks nonnative fish into northern
leatherside chub habitat (UDWR 2009, p. 32). This Statewide policy
specifies protocols for the introduction of nonnative species into Utah
waters and states that all stocking actions must be consistent with
ongoing recovery and conservation actions for State of Utah sensitive
species, including northern leatherside chub. The Nevada Board of
Wildlife Commissioners has enacted Commission Policy Number 33, which
states that waters or reaches of waters managed as ``wild'' or
``native'' will not be stocked with hatchery trout (State of Nevada
Board of Wildlife Commissioners 1999, p. 5). This includes northern
leatherside chub waters; therefore, no stocking is done within the
range of the species in Nevada (Johnson 2011b, pers. comm.). In
Wyoming, northern leatherside chub waters were historically stocked.
There is now better awareness of northern leatherside chub-occupied
habitat, and the State generally does not stock in these waters (Miller
2011, pers. comm.). The State of Idaho operates similar to Wyoming, and
there is an informal policy that discourages stocking of salmonids in
northern leatherside chub habitat (Grunder 2011, pers. comm.). Although
we did not rely on these policies for our finding, the implementation
of such policies affords adequate protection to northern leatherside
chub. These policies are not expected to change in the future.
Water Rights
To a considerable extent, water rights are managed under State law
in the four States with northern leatherside chub-occupied habitat. The
doctrine of prior appropriation or ``first in time--first in right'' is
the basis for administering surface water rights, and each State does
so via a State agency, a State Engineer, or some combination of the two
(BLM 2001, entire). As discussed under Factor A (Water Development),
much of the northern leatherside chub-occupied habitat was historically
impacted by surface water development and diversion. Currently,
occupied subwatersheds in Utah and Idaho are closed to new water
appropriations for any significant consumptive use such as large-scale
irrigation (Dean 2011, pers. comm.; Jordan 2011, pers. comm.). However,
subwatersheds occupied by northern leatherside chub in Nevada and
Wyoming are still open to new water appropriations (Randall 2011, pers.
comm.; Jacobs and Brosz 2000, p. 7). As described under Factor A (Water
Development), this level of water development is not a significant
threat to extant populations of northern leatherside chub because
populations are able to reoccupy temporarily dewatered areas when flows
return, and because low water conditions do not threaten the species
because they evolved to persist in drought conditions. Future water
development in Utah and Idaho is limited, and limited increases in
surface water usage are predicted for Nevada (Randall 2011, pers.
comm.) and Wyoming (Schroeder and Hinckley 2007, pp. 6-2 to 6-4) within
the range of the species, indicating that water development in these
States is not a significant threat, nor is it likely to become so.
Available information indicates that the State regulatory mechanisms in
existence adequately protect the northern leatherside chub from the
threat of reduction of habitat due to water development projects.
Federal Mechanisms
The major Federal mechanisms for protection of northern leatherside
chub and its habitat are through the CWA section 404 permitting
process, the CWA section 303(d) impaired water body list, and the
National Environmental Policy Act (42 U.S.C. 4231 et seq.) (NEPA).
Various Executive Orders (11990 for wetlands, 11988 for floodplains,
and 13112 for invasive species) provide guidance and incentives for
Federal land management agencies to manage for habitat characteristics
essential for conservation. As explained below, Federal land management
agencies (BLM, USFS, and NPS) have legislation that specifies how their
lands are managed for sensitive species.
As stated above in the Land Management section, approximately two-
thirds of the lands in subwatersheds with northern leatherside chub are
managed by Federal land agencies, and approximately one-third of all
occupied stream miles are on these lands. The northern leatherside chub
is designated as a sensitive species by the BLM in Utah, Wyoming,
Nevada, and Idaho. The policy in BLM Manual 6840-Special Status Species
Management states: ``Consistent with the principles of multiple use and
in compliance with existing laws, the BLM shall designate sensitive
species and implement species management plans to conserve these
species and their habitats and shall ensure that discretionary actions
authorized, funded, or carried out by the BLM would not result in
significant decreases in the overall range-wide species population and
their habitats'' (BLM 2008, p. 10). BLM land management practices are
intended to avoid negative effects whenever possible, while also
providing for multiple-use mandates; therefore, maintaining or
enhancing northern

[[Page 63468]]

leatherside chub habitat is being considered in conjunction with other
agency priorities. Available information indicates that BLM management
policies are currently adequately reducing impacts to northern
leatherside chub on BLM land.
The USFS Sensitive Species Policy in Forest Manual 2670 outlines
procedures for conserving sensitive species. The policy applies to
projects executed under the 1982 National Forest Management Act (NFMA)
implementing regulations. The range of the northern leatherside chub is
within USFS Region 4 (Intermountain Region), where it is designated a
sensitive species by the USFS (USFS 2010, p. 5), and where the National
Forests have land and resource management plans developed under NFMA.
The USFS manuals and handbooks codify the agency's policy, practices,
and procedures and are sources of administrative direction for USFS
employees.
The USFS Region 4 applies practices outlined in their Soil and
Water Conservation Practices Handbook to northern leatherside chub
habitat (USFS 1988, pp. 1-71). This handbook states that the USFS will
apply watershed conservation practices to sustain healthy soil,
riparian, and aquatic systems. The handbook provides management
measures with specific criteria for implementation. For example,
Management Measure No. 11.01 states: ``The Northern and Intermountain
Regions will manage watersheds to avoid irreversible effects on the
soil resource and to produce water of quality and quantity sufficient
to maintain beneficial uses in compliance with State Water Quality
Standards.'' Irreversible effects include reduced natural woody debris,
excess sediment production that could reduce fish habitat, water
temperature and nutrient increases that could affect beneficial uses,
and compacted or disturbed soils that could cause site productivity
loss and increased soil erosion. The USFS land management practices are
intended to avoid these effects whenever possible, while also providing
for multiple-use mandates; therefore, maintaining or enhancing northern
leatherside chub habitat is being considered in conjunction with other
agency priorities. Available information indicates that USFS and BLM
management policies are adequately reducing impacts to northern
leatherside chub on USFS land.
The National Park Service Organic Act (16 U.S.C. 1 et seq.)
specifies that the NPS will ``promote and regulate the use of the
Federal areas known as national parks, monuments, and reservations * *
* which purpose is to conserve the scenery and the natural and historic
objects and the wild life therein and to provide for the enjoyment of
the same in such manner and by such means as will leave them unimpaired
for the enjoyment of future generations.'' Consequently, livestock
grazing, timber harvest, mining, and water development do not occur in
Grand Teton National Park. The 2006 NPS Management Policies' section
4.4.1.1 (Plant and Animal Population Management Principles) states that
the NPS will maintain all native plant and animal species and their
habitats inside parks. In addition, these policies state that ``the
(National Park) Service will work with other land managers to encourage
the conservation of the populations and habitats of these species
outside parks whenever possible'' (NPS 2006, p. 43). The implementation
of previously described policies should afford some protection to
northern leatherside chub. Available information indicates that NPS
statutes, regulations, and management policies adequately reduce
impacts to the species.
The NEPA provides authority for the Service to assume a cooperating
agency role for Federal projects undergoing evaluation for significant
impacts to the human environment. This includes participating in
updates to resource management plans. As a cooperating agency, we have
the opportunity to provide recommendations to the action agency to
avoid impacts or enhance conservation for northern leatherside chub and
its habitat. For projects where we are not a cooperating agency, we
often review proposed actions and provide recommendations to minimize
and mitigate impacts to fish and wildlife resources. Acceptance of our
NEPA recommendations is at the discretion of the action agency. The BLM
and USFS land management practices are intended to ensure avoidance of
negative effects to species whenever possible, while also providing for
multiple-use mandates; therefore, maintaining or enhancing northern
leatherside chub habitat is considered in conjunction with other agency
priorities. We determine that NEPA and its implementing regulations and
policies are currently adequately reducing impacts to northern
leatherside chub.
The CWA is the primary legislation protecting water quality in U.S.
aquatic habitats and establishes a process to identify and clean
polluted waters. Section 303(d) of the CWA requires each State to
develop a list of impaired waters, defined as a waterbody that does not
meet certain water-quality uses (CWA 1977, entire). States must
evaluate all existing and readily available information in developing
their lists of impaired waters (EPA 2002, p. 9). There are several
established water quality uses including drinking water supply,
swimming, and aquatic life support (EPA 2002, p. 11). To meet the
aquatic life support use, a waterbody must provide suitable habitat for
a balanced community of aquatic organisms (EPA 2002, p. 11). Best
professional judgment, along with numeric and narrative criteria
created by the State and the EPA, is considered when evaluating the
ability of a water body to serve its uses.
Northern leatherside chub population areas contain wetland and
stream habitats, and section 404 of the CWA regulates fill in wetlands
and streams that meet certain jurisdictional requirements. Activities
that result in fill of jurisdictional wetland and stream habitat
require a section 404 permit. We can review permit applications and
provide recommendations to avoid and minimize impacts and to implement
conservation measures for fish and wildlife resources, including the
northern leatherside chub. However, incorporation of Service
recommendations into section 404 permits is at the discretion of the
U.S. Army Corps of Engineers (Corps). In addition, not all activities
in wetlands or streams involve fill and not all wetlands or streams
fall under the jurisdiction of the Corps. Regardless, earlier in this
finding we evaluated threats to northern leatherside chub habitat where
fill of wetlands or streams may occur, including mining and oil and gas
development. We found no information indicating that impacts from
stream or wetland fill are acting on the species to the point that the
species itself may be at risk, nor is it likely to become so.
Summary of Factor D
Available information indicates that land management regulatory
mechanisms are sufficiently minimizing and mitigating potential threats
from land development to extant northern leatherside chub populations.
The BLM and USFS continue to work with permittees on Federal lands to
implement beneficial land use practices and minimize impacts. The BLM
and USFS have provided protective mechanisms for conservation agreement
and sensitive species, including the northern leatherside chub, which
can minimize impacts from oil and gas drilling, mining, and grazing. We
have the ability to comment on NEPA evaluations for other projects on
BLM

[[Page 63469]]

and USFS lands that may impact the northern leatherside chub. The NPS
mandate to conserve wildlife and leave it unimpaired has allowed NPS
lands to currently be adequately and sufficiently protected and will
sufficiently minimize future threats on NPS-managed lands. As discussed
above, the BLM, USFS, and NPS are also signatories to the ``Rangewide
Conservation Agreement and Strategy for Northern Leatherside'', the
goals of which are to ensure the long-term persistence of the northern
leatherside chub and to support the development of multi-State
conservation efforts through coordinated conservation actions and
regulatory consistency. As signatories to this conservation strategy
these agencies are addressing issues related to the northern
leatherside chub.
Although regulatory mechanisms are not in place to sufficiently
protect the northern leatherside chub from local or large-scale water
withdrawal and development in Wyoming and Nevada, projected development
in these States should be minimal in the areas where northern
leatherside chub occurs (see Factor A: Water Development for more
information regarding water withdrawal and development). We found no
information that inadequacy of existing regulatory mechanisms may act
on this species to the point that the species itself may be at risk,
nor is it likely to become so.

Factor E. Other Natural or Manmade Factors Affecting Its Continued
Existence

Natural and manmade threats to northern leatherside chub include:
(1) Hybridization; (2) climate change; and (3) cumulative effects of
all activities that may impact the species.
Hybridization
Hybridization can be a concern for some fish populations. An
introgressed population can result when a genetically similar species
is introduced into or invades northern leatherside chub habitat, the
two species interbreed (i.e., hybridize), and the resulting hybrids
survive and reproduce. If the hybrids backcross with one or both of the
parental species, genetic introgression occurs (Schwaner and Sullivan
2009, p. 198). Continual introgression can eventually lead to the loss
of genetic identity of one or both parent species, thus resulting in a
``hybrid swarm'' consisting entirely of individual fish that often
contain variable proportions of genetic material from both of the
parental species (Miller and Behnke 1985, p. 514).
Hybridization is commonly associated with disturbed environments
(Helfman 2007, p. 215) because in natural, complex habitats, different
species are able to reproduce separately by using different habitat
types. Additionally, disturbances allow dispersal of species to
habitats where they did not naturally occur. For example, water
diversions and transfers may allow isolated habitat that previously
held distinctly separate populations (allopatric) to overlap habitats
(sympatric) and present an opportunity for hybridization to occur.
We are aware of a historical record that fish collections from
Sulphur Creek in the Bear River subregion contained redside shiner x
leatherside chub hybrids and that it is possible for leatherside chub
to hybridize with speckled dace (Baxter and Stone 1995, pp. 70-71);
however, we do not know how this determination was made (i.e.,
morphologically or via genetic analysis), or when these fish were
collected. Northern leatherside chub populations coexist with speckled
dace in La Chapelle, Mill, Sulphur, and Yellow Creeks, where both
species are native to these drainages (Amadio et al. 2009, p. 1).
Examination of northern leatherside chub from these drainages using
morphological characteristics suggested that populations in La Chapelle
Creek and Yellow Creek were genetically pure, but that specimens from
the other two creeks exhibited intermediate morphological
characteristics of both species, thereby suggesting potential
hybridization. However, subsequent genetic analysis determined that
there was no evidence of genetic mixing; thus we conclude that
hybridization is not occurring in these drainages at significant levels
(Amadio et al. 2009, entire). Although no other hybridization-specific
studies were conducted on northern leatherside chub, other recent
genetic investigations have not documented hybridization in extant
northern leatherside chub populations (Johnson and Jordan 2000, entire;
Johnson et al. 2004, entire).
In summary, recent examination of northern leatherside chub from
habitats where potential northern leatherside chub hybrids were
historically found has determined that hybridization is not present.
Genetically pure northern leatherside chub still occur at these sites,
and no new evidence of hybridization has surfaced. Despite the
historical supposition of hybridization in some localized areas, there
are no known new occurrences. We found no information that
hybridization may act on this species to the point that the species
itself may be at risk, nor is it likely to become so.
Climate Change
Stream conditions across the range of the northern leatherside chub
are shaped by regional climatic conditions, primarily precipitation and
temperature. Water and precipitation is limited in this arid region.
Seasonally, conditions range from cold, snowy winters to hot, dry
summers. Annually, extended oscillations between wet and dry periods
also are common (Barnett et al. 2008, p. 1080). Hydrological patterns
are dominated by high-elevation snow accumulation that subsequently
supports spring runoff and groundwater recharge (Haak et al. 2010, p.
1). Northern leatherside chub evolved in this arid ecosystem,
demonstrating their ability to withstand historical climatic
variability, including drought conditions.
Predictions of future climatic conditions can no longer rely on
analysis of past climatic trends, but must instead take into account
predicted global climate change. Both the Intergovernmental Panel on
Climate Change and the U.S. Global Climate Change Program conclude that
changes to climatic conditions, such as temperature and precipitation
regimes, are occurring and are expected to continue in western North
America over the next 100 years (Parson et al. 2000, p. 248; Smith et
al. 2000, p. 220; Solomon et al. 2007, p. 70, Table TS.76; Trenberth et
al. 2007, pp. 252-253, 262-263). Climate variability adds uncertainty
to predictions of water availability in stream systems, both in volume
of water and timing of flows (Haak et al. 2010, p. 2). Therefore, it is
important to consider how future climatic conditions may impact
northern leatherside chub.
In western North America, surface warming and precipitation changes
resulting in reduced mountain snowpack (Trenberth et al. 2007, p. 310;
Mote et al. 2005 and Regonda et al. 2005, cited in Vicuna and Dracup
2007, p. 330) and a trend toward earlier snowmelt (Stewart et al. 2004,
pp. 217, 219, 223) are climatic conditions most likely to impact stream
ecosystems (Field et al. 2007, p. 619; EPA 2008, p. 11; American
Fisheries Society 2010, p. 7). Less snow accumulation, along with
earlier and more rapid snowmelt, can affect physical ecosystem
properties in many ways, such as: Reducing aquifer recharge and
groundwater supplies for consistent stream flows; increased water
temperatures associated with lower summer stream flows; increased
spring flooding from rain storms onto snowpack; increased wildfire risk
from earlier snowmelt and drier vegetation;

[[Page 63470]]

and prolonged drought conditions (American Fisheries Society 2010, p.
11; many citations in Haak et al. 2010, p. 2). The alterations,
especially reduction in consistent flows and increased water
temperatures, also will have a myriad of biotic ecosystem effects,
including: Reduction in available aquatic habitat and resources
(increasing competition, while simultaneously reducing carrying
capacity); alteration of migration and reproduction patterns; shifting
species assemblages as suitable conditions move geographically; and
increased nonnative species invasions (Helfman 2007, pp. 185-186;
American Fisheries Society 2010, p. 11). Out of this large set of
impacts, we will analyze the following potential impacts of climate
change on northern leatherside chub because they are the most likely to
negatively impact the species: Increased chance of extreme events
(spring floods, severe wildfire, and prolonged drought); shift in
distribution to higher elevation or latitude; and upstream shift of
nonnative trout.

Increased Chance of Extreme Events

The first potential impact from climate change is increased
likelihood of extreme events, such as spring floods, wildfire, and
drought. Because northern leatherside chub populations mostly occur in
small, localized areas and in smaller streams, a localized extreme
event that alters stream conditions to lethal levels could extirpate a
local population isolated or fragmented from other populations.
Furthermore, isolated populations are at a greater risk of extirpation
because recolonization following the event may be precluded (American
Fisheries Society 2010, p. 9). The three most likely extreme events
that would affect northern leatherside chub are atypical spring floods,
severe wildfire, and prolonged drought. Northern leatherside chub
seemingly have a tolerance of short-term, extreme environmental
conditions (Belk and Johnson 2007, pp. 70-71), suggesting the species
may be able to adapt to short-term disturbances resulting from climate
change.
Uncharacteristic flooding may be a large stressor for fish species
(Williams et al. 2009, p. 533; American Fisheries Society 2010, p. 7),
especially small-bodied individuals (Harvey 1987, p. 851) like the
northern leatherside chub. A flood event could wash individuals from
local habitats, carrying them downstream to unsuitable habitats, such
as reservoirs, mainstem channels, or even onto upland habitat, or could
cause direct mortality (Poff 2002, p. 1500). Even if individuals
survived, they may not be able to return to their native location if
they were carried over fish barriers. As an example of this for closely
related minnow species, biologists hypothesize that a monsoonal flood
event in Clay Creek, a tributary to the East Fork of the Sevier River,
may be responsible for the extirpation of aquatic populations,
including the southern leatherside chub (Golden et al. 2009, p. 2;
Borden and Cox 2010, p. 2). The likelihood of entrainment during flood
conditions is reduced because canals carry less percentage of the river
into the canal and during high flows, most canals are closed to
preserve infrastructure and fields likely have enough water.
All species of native fish could be impacted by wildfire effects,
elevating the topic to a primary concern for western forest ecosystem
management (Rinne 2004, p. 151). Severe wildfires (complete denuding of
landscape and death of all vegetation) can alter stream systems both
instantaneously (ash inputs changing water chemistry or flames heating
stream water) and chronically (debris and sediment inputs from denuded
uplands, or water warming from lack of riparian vegetation) (multiple
citations in American Fisheries Society 2010, p. 9). These changes
cannot only cause fish mortality and population loss, but also have
long-term effects on the food web through macroinvertebrate mortality
(Rinne 1996, p. 653). Severe wildfire events have caused documented
local extirpation events for multiple salmonid populations in the
western United States (Rinne 1996, p. 653; 2004, p. 151), but in areas
where nearby source populations exist, recolonization has occurred
(Howell 2006, p. 983). We expect similar responses from northern
leatherside chub because severe wildfires often produce conditions that
are more extreme than the occupied habitats discussed in previous
sections, such as under Factor A: Grazing. Additional impacts arise
from fire suppression efforts that can create physical disturbances
(increased erosion and overland flow, temporary reduction or cessation
of flows in small streams when drafting or dipping water (Backer et al.
2004, p. 939, Table 1), or chemical disturbances (commonly used fire
retardants and suppressant foams are toxic to aquatic species))
(Gaikowski et al. 1996, p. 252; Buhl and Hamilton 2000, p. 408;
McDonald et al. 1996, p. 63). It is possible that a severe wildfire
could threaten northern leatherside chub through both immediate and
long-term effects.
Northern leatherside chub are resilient to moderate wildfire
conditions (charred landscape but some vegetation remains). For
example, a 1991 fire centered in the Trail Creek portion of the
Jackknife Creek subwatershed (Snake River subregion) did not extirpate
the population (Isaak and Hubert 2001, p. 27). Five years after the
fire, individuals were found in multiple locations throughout the
Jackknife Creek subwatershed, indicating population persistence (Isaak
and Hubert 2001, pp. 26-27). It is worth noting that the entire
subwatershed was not burned and that individuals caught in 1996 may be
emigrants from a nearby population from the tributary Squaw Creek.
Regardless, northern leatherside chub were found to be persisting in
the still degraded post-fire Trail Creek area, with stream temperatures
often exceeding 23 [deg]C (73 [deg]F) in the summer because of a lack
of riparian cover (Isaak and Hubert 2001, p. 27).
Prolonged drought is the third category of extreme event we
considered as a potential threat to northern leatherside chub.
Prolonged drought alters stream conditions by reducing available water,
leading to diminished habitat and habitat of lower quality (e.g.,
increased temperature, decreased oxygen) (Helfman 2007, p. 184). The
presence of suitable water conditions in streams is fundamentally
linked to the distribution, reproduction, fitness, and survival of fish
species (Helfman 2007, p. 97; American Fisheries Society 2010, p. 7).
Less available habitat space causes niches to overlap, increasing
predatory pressure on prey species and competitive pressures throughout
the food web, and causing an overall reduction in carrying capacity and
supported biomass (Helfman 2007, p. 13). Northern leatherside chub
diets overlap with many other native fish species (Bell and Belk 2004,
p. 414), and they are a prey species for others, demonstrating that
these biotic effects could potentially arise.
Prolonged drought also has a human component, as drought conditions
generally lead to increased irrigation demands on stream and
groundwater resources (Alley et al. 1999, pp. 20-21). This suggests
that human demands could exacerbate natural drought conditions created
by climate change (EPA 2008, p. 12). Additionally, within the Bear
River subbasin, irrigation canals might take larger percentages of the
river flow in low-flow years, which would likely entrain a
correspondingly higher percentage of fish, including northern
leatherside chub (Gale et al. 2008, p. 1546), but the relationship may
not be one to one (Hanson 2001, p. 331).
All of these disturbance events currently occur in localized areas
across the species' range. Nevertheless, future

[[Page 63471]]

climate conditions may increase the severity or frequency of the events
(EPA 2008, p. 11). To test this possibility, the USGS and Trout
Unlimited recently analyzed how predicted future climatic conditions
would alter the risk of extreme floods, wildfire, and drought for all
subbasins containing inland native trout species. With this information
they produced risk classifications applied at the subwatershed scale
(Haak et al. 2010, pp. 1-16; Service 2011, pp. 1-4). Because the risk
of these three events are species-independent (results are based on
climate, elevation, etc., and not species characteristics), and because
northern leatherside chub distribution overlaps with Yellowstone,
Bonneville, and Colorado River cutthroat trout, the risk models created
in this report can be applied to all extant northern leatherside chub
populations.
Researchers used existing broad-scale data, combined with local
drainage characteristics, to describe potential future disturbance
regimes (Haak et al. 2010, pp. 5-16). Using their results, we
determined potential risk to northern leatherside chub populations from
these disturbances. All extant northern leatherside chub populations
had a low risk of extreme winter flooding except the three populations
in the Goose Creek subbasin, which had moderate risk resulting from a
future forecasted transition from snow to snow/rain mix (Table 10)
(Haak et al. 2010, pp. 9, 30, 59; Service 2011, pp. 1-4). Rangewide,
all northern leatherside chub populations occur in watersheds assessed
at high risk for increased wildfires because they inhabit elevational
bands that are expected to have earlier snowmelt and subsequent longer
fire seasons, except the Goose Creek subbasin (Table 10) (Haak et al.
2010, pp. 12, 30, 59; Service 2011, pp. 1-4). However, wildfire effects
will likely be local in scale and we expect northern leatherside chub
can either retreat to habitat refuges during a fire, or recolonize
extirpated areas after a fire has ended because most populations have a
recolonization potential. All populations except for the Pacific Creek
population (moderate risk from higher elevation and higher mean
precipitation) were at a high risk for future forecasted drought
impacts (Table 10) (Haak et al. 2010, pp. 15, 31, 60; Service 2011, pp.
1-4).

Table 10--Risk Assessment of Northern Leatherside Chub Populations [Haak et al. 2010]
----------------------------------------------------------------------------------------------------------------
Risks classifications from USGS climate change paper
National hydrography dataset Population -----------------------------------------------------------------
subbasin Flood Wildfire Drought
----------------------------------------------------------------------------------------------------------------
Upper Bear................... Upper Mill/ Low................. High................ High.
Deadman Creeks.
Upper Sulphur/ Low................. High................ High.
La Chapelle
Creeks.
Yellow Creek... Low................. High................ High.
Upper Twin Low................. High................ High.
Creek.
Rock Creek..... Low................. High................ High.
Central Bear................. Dry Fork Smiths Low................. High................ High/Moderate.
Fork.
Muddy Creek.... Low................. High................ High.
Snake Headwaters............. Pacific Creek.. Low................. High................ Moderate.
Salt River................... Jackknife Creek Low................. High................ High.
Goose Creek.................. Trapper Creek.. Moderate............ Low................. High.
Beaverdam Creek Moderate/High....... Low................. High.
Trout Creek.... Moderate/High....... Low................. High.
Upper Green River/Slate Creek North Fork Low................. High................ High.
Slate Creek.
Blacks Fork.................. Upper Hams Fork Low................. High................ High/Moderate.
----------------------------------------------------------------------------------------------------------------

This analysis demonstrates that most subwatersheds harboring
northern leatherside chub (11 of 14) are at risk for increased wildfire
impacts. Even more strikingly, all extant northern leatherside chub
populations are at risk for increased drought conditions because local
conditions will not mitigate predicted regional extreme drought.
However, most northern leatherside chub populations (11 of 14) are not
at risk for increased flooding caused by earlier rain on snow events.
Based on this analysis we conclude that enhanced spring flooding is
not a threat to populations of northern leatherside chub because only a
fraction of the populations are at risk from this factor. Northern
leatherside chub populations assessed at moderate to moderate/high risk
of spring flooding occur in the Goose Creek subbasin, Snake River
subregion. Spring flooding could be a factor or become a threat
depending upon the magnitude of the flooding event, which could
displace fish downstream into reservoir habitats where predation is a
concern or strand individuals into unsuitable habitats or out of the
water channel.
Although there is evidence that wildfire risks will increase, we
conclude that wildfire also is not a substantial risk to the entire
species, because wildfires and wildfire effects will likely be local in
scale relative to the large, multi-state, widely distributed range of
the species. Local wildfires may extirpate populations, but we expect
northern leatherside chub can either retreat to habitat refuges during
a fire, or recolonize extirpated areas after a fire has ended because
most populations have a recolonization potential (see discussion under
Factor A: Fragmentation and isolation section). We hypothesize that a
similar mechanism took place in Jackknife Creek in the early 1990s,
allowing the population to persist after a wildfire.
Increased drought is a predicted rangewide problem for northern
leatherside chub populations (Table 10). While this species evolved in
an arid region and dealt with historical drought conditions, human
modifications to riverine systems for water consumption (irrigation
diversions, reservoir construction and management, municipal water use,
etc.) have greatly altered the natural hydrology over the past 200
years. Therefore, current conditions, including human water
development, must be analyzed. An analysis of water development in
extant population locations indicates that dewatering is not common in
most populations, suggesting that these populations have elasticity to
deal with lower water availability in the future. In addition, northern
leatherside chub are documented to persist in degraded habitats, such
as remnant pools, and seem to persist in short-term low water
conditions (Belk and Johnson 2007, p.

[[Page 63472]]

71). Because of these adaptations to deal with harsh conditions, and
their ability to shift habitats as drought conditions warrant, drought
has a limited effect on the species rangewide. We found no information
that drought may act on this species to the point that the species
itself may be at risk, nor is it likely to become so.

Northern Leatherside Chub and Nonnative Trout Habitat Shifts

Large-scale climatic warming trends are expected to result in
warmer water temperatures nationwide (EPA 2008, p. 8). Because water
temperature is a keystone feature of fish community distribution,
predicted changes are expected to negatively affect cold-water
fisheries continent-wide and cool-water fisheries in the southern
latitudes, while benefiting warm-water species continent-wide and cool-
water species in the northern latitudes (Field et al. 2007, p. 631).
Northern leatherside chub are adapted to warmer water temperatures,
including seasonal water temperature changes associated with late
summer baseflows in mid-elevation streams (Wilson and Belk 2001, p. 39;
Belk and Johnson 2007, p. 71). As such, northern leatherside chub may
not be as vulnerable to warming water trends as cold-water species such
as brook trout.
Where suitable upstream habitats are available and stream gradient
permits, we expect that northern leatherside chub populations can
transition upstream, tracking suitable habitat conditions. Across the
range of the species, most extant northern leatherside chub populations
occur in mid-headwater reaches with upstream habitat often unoccupied
by individuals. For example, for a few populations in the Bear River
and Green River subregions, their upstream distribution is demarcated
by the presence of brook trout or possibly cooler water temperatures,
which are predicted to shift upstream and decline as water temperatures
warm if forecasted climate change impacts occur (Field et al. 2007, p.
624).
If predicted water temperatures conditions change across the range
of the northern leatherside chub, the distribution of other fish
species will shift as well, including those that could impact northern
leatherside chub (see discussion under Factor C: Predation). Low water
temperatures are believed to currently restrict the distribution of
brown trout (Sigler and Sigler 1996, p. 206), suggesting that region-
wide warming water temperatures may benefit the species through
increasing suitable upstream habitats. On the other hand, because
rainbow trout are able to tolerate more wide-ranging water temperatures
(Sigler and Sigler 1996, p. 184), their distribution may only
moderately change.
Because brown trout are more tolerant of warmer waters than other
trout species, increased stream temperatures as a result of climate
change effects may allow brown trout populations to expand their range
upstream and possibly impact three populations of northern leatherside
chub, two in the central Bear River subbasin and one in the Salt River
subbasin. For example, brown trout in lower Jackknife Creek are
currently limited by cooler water temperatures and may be able to
migrate (shift) upstream if increasing water temperatures result from
climate change effects, as there are no physical barriers to movement.
Although the Jackknife Creek leatherside chub population may be
vulnerable to any future brown trout upstream re-distribution from
warming waters, it is unclear how Jackknife Creek water temperatures
will change, and how chub and brown trout will respond in terms of
migration into currently unoccupied upstream and adjacent tributary
habitats. Because northern leatherside chub currently occur in an
approximately 13-km reach and at least two adjacent tributaries, it is
highly unlikely that the species would be eliminated throughout this
reach in the event brown trout redistributed upstream in response to
warming water temperatures. Northern leatherside chub populations in
the Dry Fork Smiths Fork or Muddy Creek (Bear River subregion) are not
considered vulnerable to future impacts from downstream brown trout
populations as a result of climate change, as existing fish passage
barriers and degraded habitat conditions will likely inhibit their
movement.
We expect that the distribution of existing rainbow trout
populations will likely remain similar to today, or only change
moderately because they are thermal generalists. Rainbow trout overlap
with two extant northern leatherside chub populations, and any existing
impacts are not likely to increase as a result of climate change.
Brook trout populations will likely be negatively impacted by
climate change because they are a cold-water fish (Sigler and Sigler
1996, p. 212). We expect any future climate change effects will reduce
brook trout abundance upstream of extant northern leatherside chub
populations (i.e., brook trout occurrences that are not currently
threatening the northern leatherside chub), which could benefit
northern leatherside chub that may migrate upstream into suitable
habitats no longer inhabited by brook trout.
We found no information that warming stream temperatures may act on
this species to the point that the species itself may be at risk, nor
is it likely to become so. Northern leatherside chub are adapted to
warmer water temperatures, including seasonal water temperature changes
associated with late summer baseflows in mid-elevation streams. Most
populations occur in streams with currently upstream habitats that may
become suitable as stream temperatures change, allowing populations to
shift into currently unoccupied upstream or adjacent stream habitats.
One northern leatherside chub population in Jackknife Creek may become
vulnerable to future brown trout predation if brown trout redistribute
upstream as a result of warming waters due to climate change, although
it is unclear how Jackknife Creek water temperatures will change and
how both chub and brown trout will respond in terms of migration into
currently unoccupied upstream and adjacent tributary habitats.
Summary of Impacts of Climate Change
Because northern leatherside chub are able to survive in broad
habitat conditions and tolerate warm water temperatures (Wilson and
Belk 2001; Nannini and Belk 2006, p. 454), we believe that populations
will be resilient to small-scale abiotic changes to habitat because of
climate change (upstream habitat shift caused by temperature changes,
etc.). We also believe there is adequate upstream habitat to facilitate
upstream migration of populations in the face of warming stream
temperatures.
Recent modeling efforts predict increased frequency of catastrophic
events, especially increased wildfires and prolonged drought. We expect
connected, large populations to weather these disturbances with natural
demographic fluctuations. Wildfire impacts will likely take place on a
small enough geographic scale to allow some portion of northern
leatherside populations to survive, which will allow for recolonization
and population expansion after the fire has receded and habitat has
recovered. Prolonged or more frequent drought will likely occur on a
larger scale. However, we expect northern leatherside chub to persist
during these periods because individuals can survive in broad habitat
conditions and are tolerant of low water levels. While the smaller,
more isolated northern leatherside chub populations are at an increased
risk from increased frequency of possible stochastic events associated
with climate change, there is

[[Page 63473]]

still uncertainty on how, when, or if, these impacts may occur.
Shifting distributions of nonnative trout also are not expected to
create undue risk to the species. Only one population of northern
leatherside chub in Jackknife Creek may be at increased risk from
shifting nonnative trout; therefore, we believe the species as a whole
is resilient to this threat. We found no information that climate
change effects may act on this species to the point that the species
itself may be at risk, nor is it likely to become so.
Cumulative Impacts
Some of the threats discussed in this finding can work in concert
with one another to cumulatively create situations that will impact
northern leatherside chub beyond the scope of each individual threat.
For example, as discussed under Factor C: Predation, the impacts of
nonnative trout are exacerbated by drought conditions because
individual northern leatherside chub will be exposed to brown trout if
their side channel habitats are eliminated. In the absence of drought
conditions, northern leatherside chub can potentially persist in the
presence of brown trout, albeit in low densities. Similarly, in the
absence of brown trout, drought conditions are not a threat to northern
leatherside chub because the species is adapted to withstand a broad
range of habitat conditions including higher stream temperatures and
low water levels. Because of this relationship, we will analyze the
cumulative impact of drought (as a result of climate change), water
development (human-caused water reduction), and nonnative trout
presence.
We also analyze the relationship between population size,
isolation, and potential threats. Dense, connected populations are able
to withstand impacts more vigorously than small, isolated populations.
Dense populations are able to lose individuals without a corresponding
loss of the entire population, but small populations are vulnerable if
even a few individuals are lost. Similarly, connected populations are
more secure from threats because nearby populations can provide rescue
effects (immigrants and recolonization). In contrast, isolated
populations have no potential to be rescued, so local extirpation is
likely permanent.

Drought, Water Development, and Nonnative Trout

As mentioned previously, when nonnative trout are present, drought
conditions greatly intensify northern leatherside chub mortality risk.
Five northern leatherside populations harbor nearby or resident
populations of rainbow or brown trout (Table 7): Dry Fork Smiths Fork
and Muddy Creeks in the Bear River subregion; Jackknife and Trapper
Creeks in the Snake River subregion; and Upper Hams Fork in the Green
River subregion. All five of these populations have either high or
moderate-to-high risk of increased drought from climate change (Table
10); however, none of these five populations have experienced
dewatering events in the past (Table 5), indicating that natural flow
(not irrigation) conditions will drive the water supply for habitat.
Increased drought will not increase the risk of nonnative trout in
the Dry Fork Smiths Fork or Muddy Creek populations because lower water
conditions will only reduce the chance of brown trout invasion. As a
result of decreased water supply, Muddy Creek habitat conditions will
become even less suitable for trout and Dry Fork Smiths Fork will be
even more isolated by culverts.
We believe that the northern leatherside chub populations in the
Upper Hams Fork and Trapper Creek will become more impacted by the
resident rainbow trout in drought conditions. However, the low density
of rainbow trout and the high density of northern leatherside chub in
the Upper Hams Fork do not put this population at risk of extirpation.
The Trapper Creek northern leatherside chub population is less dense
and could experience more of an impact from rainbow trout predation in
drought conditions than Upper Hams Fork.
Under drought conditions as a result of climate change, habitat
conditions in the Jackknife Creek subwatershed may facilitate upstream
movement by brown trout. Such warming conditions will initially be
within the tolerable range of northern leatherside chub, but may expand
the availability of brown trout habitat. However, with the possible
exception of the northern leatherside chub population in Jackknife
Creek, the species should be resilient to small-scale abiotic changes
to habitat because of climate change (upstream habitat shift caused by
temperature changes, etc.) and there is likely adequate upstream and
nearby tributary habitats to adapt to under future drought conditions.

Drought and Water Quality

Two northern leatherside chub populations that occur in streams
listed as 303(d) water quality impaired (Beaverdam and Trapper Creeks)
may be at increased risk due to future drought severity effects (Table
10). The water quality impairments in these streams that would likely
impact northern leatherside chub (elevated sediment and phosphorous,
and low dissolved oxygen) would be exacerbated under lower flow
conditions that result from future drought conditions. However, because
there is no current information on how impaired water quality may be
impacting existing northern leatherside chub populations, we cannot
predict how future drought conditions will effect the species' habitats
or water quality.

Population Fragmentation and Isolation in Relation to Other Threats

As demonstrated in the preceding section, impacts that do not
threaten northern leatherside chub independently may work together and
have substantial, cumulative impacts. In this analysis, we will analyze
the cumulative impacts to populations and the species as a whole,
paying particular attention to population isolation and fragmentation.
In the preceding analysis, we determined that 7 of 14 northern
leatherside chub populations were isolated, and 6 of 14 contained only
a single documented occurrence of the species (see Factor A discussion
and Table 6). Because 3 populations were both isolated and contained a
single occurrence, the remaining 11 populations were considered
sufficiently resilient in terms of population size and distribution
(connected to other occurrences or populations) and only minimally
impacted from the previously analyzed threats and, therefore, not at
increased vulnerability from various threat factors due to isolation
and fragmentation.
Summary of Factor E
Recent examination of northern leatherside chub from habitats where
suspected hybrids were historically found has determined that
hybridization is not present. Therefore, with no known instances of
hybridization, we conclude that hybridization is not a threat to
northern leatherside chub.
Projected impacts from future climate change effects will likely
impact all northern leatherside chub populations to some degree,
although the synergistic effect of these impacts with identified and
potential threats are uncertain. Because stable, reproducing northern
leatherside chub populations occur at many locations where degraded
habitat conditions exist, their continued persistence and successful
reproduction demonstrates that they have some level of tolerance for
less than optimal environmental conditions. We found no

[[Page 63474]]

information that other natural or manmade factors affecting its
continued existence may act on this species to the point that the
species itself may be at risk, nor is it likely to become so.

Finding

As required by the Act, we considered the five factors in assessing
whether the northern leatherside chub (Lepidomeda copei) is endangered
or threatened throughout all or a significant portion of its range. We
examined the best scientific and commercial information available
regarding the past, present, and future threats faced by the northern
leatherside chub. We reviewed the petition, information available in
our files, other available published and unpublished information, and
we consulted with recognized northern leatherside chub experts, other
Federal and State agencies, and university researchers. We also
prepared a white paper that analyzed specific issues to the species. In
considering what factors might constitute threats, we must look beyond
the mere exposure of the species to the factor to determine whether the
species responds to the factor in a way that causes actual impacts to
the species. If there is exposure to a factor, but no response, or only
a positive response, that factor is not a threat. If there is exposure
and the species responds negatively, the factor may be a threat and we
then attempt to determine how significant a threat it is. If the threat
is significant, it may drive or contribute to the risk of extinction of
the species such that the species warrants listing as endangered or
threatened as those terms are defined by the Act. This does not
necessarily require empirical proof of a threat. The combination of
exposure and some corroborating evidence of how the species is likely
impacted could suffice. The mere identification of factors that could
impact a species negatively is not sufficient to compel a finding that
listing is appropriate; we require evidence that these factors are
operative threats that act on the species to the point that the species
meets the definition of endangered or threatened under the Act.
Northern leatherside chub are a small, mid-elevation fish endemic
to streams within the Bear River, Upper Green River, and Upper Snake
River Basins. The range of the northern leatherside chub has declined
over the past 50 years, and there are currently 14 extant populations
spread over the Bear (7), Snake (5) and Green (2) River subregions. The
species evolved in an arid ecosystem characterized by extreme seasonal
and annual changes in physical conditions.
The most widely distributed, relatively large populations occur in
the Bear River subregion. Most populations in the Bear River subregion
are largely free of threats (Upper Mill/Deadman Creeks), contain
multiple populations, can easily interact (Upper Twin Creek and Rock
Creek), and include relatively high-density populations (Upper Mill/
Deadman Creeks, Yellow Creek, Dry Fork Smiths Fork, Muddy Creek, Rock
Creek, and Upper Twin Creek). As a result, we concluded that the size,
connectedness, and stability of the Bear River populations are
sufficient to ensure the long-term persistence of the species as a
whole. Although less monitoring and collection information is available
to characterize northern leatherside chub populations within the Snake
River subbasin, most extant populations in the Snake River subbasin are
discontinuous from other populations and have relatively low population
numbers. Three of five Snake River populations have one or more factors
affecting each population, primarily impaired water quality and
nonnative trout. These and other factors were not considered
significant or imminent. We do not fully understand how these current
or potential threats are impacting the species, and it is believed that
northern leatherside chub tolerate some level of degraded or short-
term, extreme conditions. Although the isolation of some Snake River
populations likely increases their vulnerability to the effects of
identified threats, these threats do not currently or in the
foreseeable future pose a substantial risk to species rangewide.
When evaluating the potential impact to northern leatherside chub
and their habitat from future climate change effects, it is likely that
warming water temperatures predicted to occur will likely benefit the
species, especially in those stream systems with currently unoccupied
habitats upstream. The species is tolerant of short-term extreme
environmental conditions, suggesting the species may be able to survive
some of the shorter-term disturbances from climate change. Because of
the uncertainty associated with future climate change predictions, the
synergistic effect of future climate change scenarios, with identified
or potential threats on stream systems where the northern leatherside
chub occurs, are unknown.
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 northern leatherside chub is in danger of extinction
(endangered), or likely to become endangered within the foreseeable
future (threatened), throughout its range. Therefore, we find that
listing the northern leatherside chub as an endangered or threatened
species throughout its range is not warranted at this time.

Significant Portion of the Range

Having determined that the northern leatherside chub is not
endangered or threatened throughout its range, we must next consider
whether there are any significant portions of the range where the
northern leatherside chub is in danger of extinction or is likely to
become endangered in the foreseeable future.
The Act defines ``endangered species'' as any species which is ``in
danger of extinction throughout all or a significant portion of its
range,'' and ``threatened species'' as any species which is ``likely to
become an endangered species within the foreseeable future throughout
all or a significant portion of its range.'' The definition of
``species'' is also relevant to this discussion. The Act defines
``species'' as follows: ``The term `species' includes any subspecies of
fish or wildlife or plants, and any distinct population segment [DPS]
of any species of vertebrate fish or wildlife which interbreeds when
mature.'' The phrase ``significant portion of its range'' (SPR) is not
defined by the statute, nor addressed in our regulations: (1) The
consequences of a determination that a species is either endangered or
likely to become so throughout a significant portion of its range, but
not throughout all of its range; or (2) what qualifies a portion of a
range as ``significant.''
Two recent district court decisions have addressed whether the SPR
language allows the Service to list or protect less than all members of
a defined ``species'': Defenders of Wildlife v. Salazar, 729 F. Supp.
2d 1207 (D. Mont. 2010), concerning the Service's delisting of the
Northern Rocky Mountain gray wolf (74 FR 15123, April. 2, 2009); and
WildEarth Guardians v. Salazar, 2010 U.S. Dist. LEXIS 105253 (D. Ariz.
Sept. 30, 2010), concerning the Service's 2008 finding on a petition to
list the Gunnison's prairie dog (73 FR 6660, February. 5, 2008). The
Service had asserted in both of these determinations that it had
authority, in effect, to protect only some members of a ``species,'' as
defined by the Act (i.e., species, subspecies, or DPS), under the Act.
Both courts ruled that the determinations were arbitrary and capricious
on the grounds that this

[[Page 63475]]

approach violated the plain and unambiguous language of the Act. The
courts concluded that reading the SPR language to allow protecting only
a portion of a species' range is inconsistent with the Act's definition
of ``species.'' The courts concluded that once a determination is made
that a species (i.e., species, subspecies, or DPS) meets the definition
of ``endangered species'' or ``threatened species,'' it must be placed
on the list in its entirety and the Act's protections applied
consistently to all members of that species (subject to modification of
protections through special rules under sections 4(d) and 10(j) of the
Act).
Consistent with that interpretation, and for the purposes of this
finding, we interpret the phrase ``significant portion of its range''
in the Act's definitions of ``endangered species'' and ``threatened
species'' to provide an independent basis for listing; thus there are
two situations (or factual bases) under which a species would qualify
for listing: A species may be endangered or threatened throughout all
of its range; or a species may be endangered or threatened in only a
significant portion of its range. If a species is in danger of
extinction throughout an SPR, it, the species, is an ``endangered
species.'' The same analysis applies to ``threatened species.'' Based
on this interpretation and supported by existing case law, the
consequence of finding that a species is endangered or threatened in
only a significant portion of its range is that the entire species will
be listed as endangered or threatened, respectively, and the Act's
protections will be applied across the species' entire range.
We conclude, for the purposes of this finding, that interpreting
the SPR phrase as providing an independent basis for listing is the
best interpretation of the Act because it is consistent with the
purposes and the plain meaning of the key definitions of the Act; it
does not conflict with established past agency practice (i.e., prior to
the 2007 Solicitor's Opinion), as no consistent, long-term agency
practice has been established; and it is consistent with the judicial
opinions that have most closely examined this issue. Having concluded
that the phrase ``significant portion of its range'' provides an
independent basis for listing and protecting the entire species, we
next turn to the meaning of ``significant'' to determine the threshold
for when such an independent basis for listing exists.
Although there are potentially many ways to determine whether a
portion of a species' range is ``significant,'' we conclude, for the
purposes of this finding, that the significance of the portion of the
range should be determined based on its biological contribution to the
conservation of the species. For this reason, we describe the threshold
for ``significant'' in terms of an increase in the risk of extinction
for the species. We conclude that a biologically based definition of
``significant'' best conforms to the purposes of the Act, is consistent
with judicial interpretations, and best ensures species' conservation.
Thus, for the purposes of this finding, and as explained further below,
a portion of the range of a species is ``significant'' if its
contribution to the viability of the species is so important that
without that portion, the species would be in danger of extinction.
We evaluate biological significance based on the principles of
conservation biology using the concepts of redundancy, resiliency, and
representation. Resiliency describes the characteristics of a species
and its habitat that allow it to recover from periodic disturbance.
Redundancy (having multiple populations distributed across the
landscape) may be needed to provide a margin of safety for the species
to withstand catastrophic events. Representation (the range of
variation found in a species) ensures that the species' adaptive
capabilities are conserved. Redundancy, resiliency, and representation
are not independent of each other, and some characteristic of a species
or area may contribute to all three. For example, distribution across a
wide variety of habitat types is an indicator of representation, but it
may also indicate a broad geographic distribution contributing to
redundancy (decreasing the chance that any one event affects the entire
species), and the likelihood that some habitat types are less
susceptible to certain threats, contributing to resiliency (the ability
of the species to recover from disturbance). None of these concepts is
intended to be mutually exclusive, and a portion of a species' range
may be determined to be ``significant'' due to its contributions under
any one or more of these concepts.
For the purposes of this finding, we determine if a portion's
biological contribution is so important that the portion qualifies as
``significant'' by asking whether without that portion, the
representation, redundancy, or resiliency of the species would be so
impaired that the species would have an increased vulnerability to
threats to the point that the overall species would be in danger of
extinction (i.e., would be ``endangered''). Conversely, we would not
consider the portion of the range at issue to be ``significant'' if
there is sufficient resiliency, redundancy, and representation
elsewhere in the species' range that the species would not be in danger
of extinction throughout its range if the population in that portion of
the range in question became extirpated (extinct locally).
We recognize that this definition of ``significant'' (a portion of
the range of a species is ``significant'' if its contribution to the
viability of the species is so important that without that portion, the
species would be in danger of extinction) establishes a threshold that
is relatively high. On the one hand, given that the consequences of
finding a species to be endangered or threatened in an SPR would be
listing the species throughout its entire range, it is important to use
a threshold for ``significant'' that is robust. It would not be
meaningful or appropriate to establish a very low threshold whereby a
portion of the range can be considered ``significant'' even if only a
negligible increase in extinction risk would result from its loss.
Because nearly any portion of a species' range can be said to
contribute some increment to a species' viability, use of such a low
threshold would require us to impose restrictions and expend
conservation resources disproportionately to conservation benefit:
Listing would be rangewide, even if only a portion of the range of
minor conservation importance to the species is imperiled. On the other
hand, it would be inappropriate to establish a threshold for
``significant'' that is too high. This would be the case if the
standard were, for example, that a portion of the range can be
considered ``significant'' only if threats in that portion result in
the entire species' being currently endangered or threatened. Such a
high bar would not give the SPR phrase independent meaning, as the
Ninth Circuit held in Defenders of Wildlife v. Norton, 258 F.3d 1136
(9th Cir. 2001).
The definition of ``significant'' used in this finding carefully
balances these concerns. By setting a relatively high threshold, we
minimize the degree to which restrictions will be imposed or resources
expended that do not contribute substantially to species conservation.
But we have not set the threshold so high that the phrase ``in a
significant portion of its range'' loses independent meaning.
Specifically, we have not set the threshold as high as it was under the
interpretation presented by the Service in the Defenders litigation.
Under that interpretation, the portion of the range would have to be so
important that current imperilment there would mean that the species

[[Page 63476]]

would be currently imperiled everywhere. Under the definition of
``significant'' used in this finding, the portion of the range need not
rise to such an exceptionally high level of biological significance.
(We recognize that if the species is imperiled in a portion that rises
to that level of biological significance, then we should conclude that
the species is in fact imperiled throughout all of its range, and that
we would not need to rely on the SPR language for such a listing.)
Rather, under this interpretation we ask whether the species would be
endangered everywhere without that portion, i.e., if that portion were
completely extirpated. In other words, the portion of the range need
not be so important that even the species being in danger of extinction
in that portion would be sufficient to cause the species in the
remainder of the range to be endangered; rather, the complete
extirpation (in a hypothetical future) of the species in that portion
would be required to cause the species in the remainder of the range to
be endangered.
The range of a species can theoretically be divided into portions
in an infinite number of ways. However, there is no purpose to
analyzing portions of the range that have no reasonable potential to be
significant or to analyzing portions of the range in which there is no
reasonable potential for the species to be endangered or threatened. To
identify only those portions that warrant further consideration, we
determine whether there is substantial information indicating that: (1)
The portions may be ``significant,'' and (2) the species may be in
danger of extinction there or likely to become so within the
foreseeable future. Depending on the biology of the species, its range,
and the threats it faces, it might be more efficient for us to address
the significance question first or the status question first. Thus, if
we determine that a portion of the range is not ``significant,'' we do
not need to determine whether the species is endangered or threatened
there; if we determine that the species is not endangered or threatened
in a portion of its range, we do not need to determine if that portion
is ``significant.'' In practice, a key part of the determination that a
species is in danger of extinction in a significant portion of its
range is whether the threats are geographically concentrated in some
way. If the threats to the species are essentially uniform throughout
its range, no portion is likely to warrant further consideration.
Moreover, if any concentration of threats to the species occurs only in
portions of the species' range that clearly would not meet the
biologically based definition of ``significant,'' such portions will
not warrant further consideration.
Decisions by the Ninth Circuit Court of Appeals in Defenders of
Wildlife v. Norton, 258 F.3d 1136 (2001) and Tucson Herpetological
Society v. Salazar, 566 F.3d 870 (2009) found that the Act requires the
Service, in determining whether a species is endangered or threatened
throughout a significant portion of its range, to consider whether lost
historical range of a species (as opposed to its current range)
constitutes a significant portion of the range of that species. While
this is not our interpretation of the statute, we first address the
lost historical range before addressing the current range.
Lost Historical Range
The available literature provides limited information on the
historical distribution of northern leatherside chub. The type locality
for the northern leatherside chub was discovered in 1881 from the
mainstem Bear River near Evanston, Wyoming (Jordan and Gilbert 1881 in
UDWR 2009, p. 39). The species is historically documented in portions
of the Bear River and Upper Snake River subregions (Figure 1; Table 1).
These historical collections demonstrate that the species existed over
a wide geographic area from Idaho, to Wyoming, and into Utah.
Specifically, historical records (during the 1950s, 1960s, and
1970s) document the existence of individuals from three subbasins
containing four locations that we consider populations today; one
population in the Snake River subregion (Pacific Creek) and three
populations in the Bear River subregion (Yellow Creek, Rock Creek, and
Muddy Creek) (McAbee 2011, pp. 10, 19). Northern leatherside chub were
also historically found in three subbasins that do not contain extant
populations (McAbee 2011, p. 2). More recent investigations documented
northern leatherside chub at two subbasins (Salt River and Goose Creek)
within the Snake River subregion, thus adding four populations
(Jackknife Creek, Trapper Creek, Beaverdam Creek, and Trout Creek) to
the accepted historical range (McAbee 2011, p. 19).
The best scientific data allow us to document the historical
existence of northern leatherside chub only at the subbasin scale.
These historical data have more recently been compared to current
distributional information to determine the presence of extant
historical populations as explained above. We conclude that the
historical range of northern leatherside chub included the following
subbasins: Upper Bear River, Central Bear River, Logan River, Lower
Bear River, Snake Headwaters, Salt River, Goose Creek, and Little Wood
River.
Over the past 50 years, the range of the northern leatherside chub
has declined, and the current range of the species is now contained in
five of the eight documented historical subbasins (Wilson and Belk
2001, p. 36; Johnson et al. 2004, pp. 841-842; UDWR 2009, p. 24).
Northern leatherside chub are likely extirpated from the Little Wood
River in Idaho, where verified museum records exist, but recent
collections failed to document any extant populations. Similarly,
northern leatherside chub are likely extirpated from the Logan and
Lower Bear Rivers in Utah and Idaho, where recent collections failed to
document extant populations, and past collection records, while
accepted as true, cannot be verified (McKay 2011, pers. comm.).
Although we acknowledge that there is some ambiguity in the
historical and current ranges of northern leatherside chub (see
Background: Distribution), we conclude that the species is extirpated
from three of the eight historically occupied subbasins: The Logan
River, Lower Bear River, and Little Wood River subbasins.
As described earlier (see Background: Distribution), despite the
loss of the three historical populations, there remain 14 northern
leatherside populations distributed across the Bear River, Upper Snake
River, and Upper Green River subregions (see Figure 1). We now consider
if the loss of the three historical populations (Logan River, Lower
Bear River, and Little Wood River) is so important that individually or
collectively this loss of range qualifies as ``significant'' by asking
whether without these portions, the representation, redundancy, or
resiliency of the species is so impaired that the species has an
increased vulnerability to threats to the point that the overall
species is in danger of extinction (see below for more information on
justification for this assessment).
Although each of the three lost northern leatherside chub subbasins
discussed above likely has features that make it unique, we determine
that the historical populations were similar geographically and
biologically to the current species' locations. For example, the
species' potential spawning, feeding, and sheltering habitat in these
locations was likely similar to current population locations (see
Background: Life History, Habitat), and all occurred within

[[Page 63477]]

subregions that are currently occupied (see Figure 1).
The loss of the three historically occupied subbasins in portions
of the species' range likely resulted in a reduction in the species
overall population, but the remaining populations are independent of
these populations and do not rely on any of the lost population's
habitat for life-history processes (e.g., spawning, feeding,
sheltering). Furthermore, this potential reduction of reproductive
output has not reduced the species' range of variation or adaptive
capabilities to such a level that they would be in danger of
extinction. Despite the loss of these three historically occupied
subbasins, the resiliency of northern leatherside chub has not been
appreciably impacted, and the species will continue to be able to
recover from periodic disturbance and withstand catastrophic events in
other parts of its range.
In summary, although the species is extirpated from three
historically occupied subbasins, the species is found in five other
historically occupied subbasins and two additional subbasins in the
Upper Green River subregion and now comprises 14 populations in these
subbasins. We conclude that these remaining 14 populations provide
sufficient representation and redundancy of northern leatherside chub
habitat throughout the species' current range such that northern
leatherside chub is not in danger of extinction despite the loss of
historical habitat. Thus, the lost historical range of northern
leatherside chub does not constitute a significant portion of the range
of the subspecies.
Current Range
After reviewing the potential threats throughout the range of
northern leatherside chub, we determine that five of fourteen
populations within the species' current range could be considered to
have concentrated threats (see discussion under Factor A, Factor C, and
Factor E). Below, we outline the elevated risk from potential threats
found at the five populations and then assess whether these portions of
the species' range may meet the definition of ``significant,'' that is,
whether the contributions of these portions of the northern leatherside
chub's range to the viability of the species is so important that
without those portions, the species would be in danger of extinction.
The Dry Fork Smiths Fork population (Central Bear River subbasin)
is isolated and likely contains only one occurrence of northern
leatherside chub, making it vulnerable to a large-scale disturbance or
stochastic event such as drought. The Pacific Creek population (Snake
Headwaters subbasin) is similarly isolated (see discussion under Factor
A: Fragmentation and Isolation of Existing Populations). In Jackknife
Creek (Salt River subbasin), a brown trout population occurs downstream
of the northern leatherside chub population (see discussion under
Factor C: Predation). Although this population currently coexists with
brown trout, there is the potential that a climate change-induced
increase in water temperature could force a habitat shift, pushing
predacious brown trout into core northern leatherside chub habitat (see
discussion under Factor E: Climate Change). The Beaverdam Creek and
Trapper Creek populations (Goose Creek subbasin) both occur in streams
listed as 303(d) water quality impaired, although aquatic communities
continue to persist (see discussion under Factor A: Water Quality).
These populations could be at increased risk if future drought
conditions occur (see discussion under Factor E: Drought and Water
Quality). The Trapper Creek population co-occurs with rainbow trout and
may be vulnerable to predation from this nonnative species (see
discussion under Factor C: Predation and Table 7). Also, this
population is isolated, making it vulnerable to a large-scale
disturbance or stochastic event such as drought (see discussion under
Factor A: Fragmentation and Isolation of Existing Populations and Table
6).
Because the northern leatherside chub faces elevated risk from
potential threats at the five population locations discussed above, we
next assess whether these portions of the species' range may meet the
biologically based definition of ``significant.'' For these areas, we
evaluate whether the populations' biological contributions are so
important that individually or collectively this hypothetical loss of
range would qualify as ``significant'' by asking whether without that
portion, the representation, redundancy, or resiliency of the species
would be so impaired that the species would have an increased
vulnerability to threats to the point that the overall species would be
in danger of extinction.
Although each of the five northern leatherside chub population
locations discussed above likely has features that make it unique, we
determine that they are similar geographically and biologically to
other species' locations. For example, the species' spawning, feeding,
and sheltering habitat is essentially the same at all population
locations (see Background: Life History, Habitat). If the Dry Fork
Smiths Fork, Pacific Creek, Jackknife Creek, Trapper Creek, and
Beaverdam Creek populations could no longer support northern
leatherside chub, other existing population locations could support the
species' persistence. The remaining nine population locations are
distributed within the species' current and historical range in the
Bear River, Upper Snake River, and Upper Green River subregions (see
Figure 1), and offer sufficient representation and redundancy of
habitat and range such that northern leatherside chub would not be in
danger of extinction if these five population locations were completely
lost.
The loss of these five populations in portions of the species'
range would directly result in a reduction in the species' overall
population size, but the loss of individual populations would not cause
a reduction in the local population size of any remaining population
because each northern leatherside chub population is independent and
does not rely on other population's habitat for life-history processes
(e.g., spawning, feeding, sheltering). Also, the loss of the five
populations would not reduce the species' range of variation or
adaptive capabilities to such a level that they would be in danger of
extinction. Without these five population locations, we expect that the
resiliency of northern leatherside chub would not be appreciably
impacted; the species would continue to be able to recover from
periodic disturbances and withstand catastrophic events in other parts
of its range.
In summary, despite having some locations of elevated risk to
potential threats, we conclude that the portions of the northern
leatherside chub's range where these threats occur are not significant
portions of its range. Even if all of these population locations were
extirpated at some time in the future, northern leatherside chub would
persist at population locations not affected by these threats. As noted
above, there is little that biologically distinguishes Dry Fork Smiths
Fork, Pacific Creek, Jackknife Creek, Trapper Creek, and Beaverdam
Creek from other population locations for northern leatherside chub.
The existing, remaining population locations are distributed across the
species' historical range in the Bear River, Upper Snake River, and
Upper Green River subregions and provide adequate redundancy,
resiliency, and representation for the species. Therefore, the five
population locations (whether considered separately or combined) are
not a ``significant'' portion of the species' range because

[[Page 63478]]

their contribution to the viability of the species is not so important
that the species would be in danger of extinction without those
portions.
We find that northern leatherside chub is not in danger of
extinction now, nor is it likely to become endangered within the
foreseeable future throughout all or a significant portion of its
range. Therefore, listing northern leatherside chub 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, northern leatherside chub to our Utah
Ecological Services Field Office (see ADDRESSES section) whenever it
becomes available. New information will help us monitor northern
leatherside chub and encourage its conservation. If an emergency
situation develops for the northern leatherside chub or any other
species, we will act to provide immediate protection.

References Cited

A complete list of references cited is available on the Internet at
http://www.regulations.gov and upon request from the Utah Ecological
Services Field Office (see ADDRESSES section).

Authors

The primary authors of this notice are the staff members of the
Utah and Idaho Ecological Services Field Offices.

Authority

The authority for this action is section 4 of the Endangered
Species Act of 1973, as amended (16 U.S.C. 1531 et seq.).

Dated: September 27, 2011.
Rowan Gould,
Acting Director, Fish and Wildlife Service.
[FR Doc. 2011-25810 Filed 10-11-11; 8:45 am]
BILLING CODE 4310-55-P