Endangered and Threatened Wildlife and Plants; 12-month Finding on a Petition To List the Mountain Whitefish in the Big Lost River, Idaho, as Endangered or Threatened, 17352-17363 [2010-7674]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 75, Number 65 (Tuesday, April 6, 2010)]
[Proposed Rules]
[Pages 17352-17363]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2010-7674]


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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[FWS-R1-ES-2009-0043]
[MO 92210-0-0008 B2]


Endangered and Threatened Wildlife and Plants; 12-month Finding 
on a Petition To List the Mountain Whitefish in the Big Lost River, 
Idaho, 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 mountain whitefish 
(Prosopium williamsoni) in the Big Lost River, Idaho, as endangered or 
threatened under the Endangered Species Act of 1973, as amended. After 
review of all available scientific and commercial information, we find 
that the mountain whitefish in the Big Lost River does not constitute a 
listable entity under the Act and, therefore, listing is not warranted. 
However, we ask the public to continue to submit to us any new 
information that becomes available concerning the taxonomy, biology, 
ecology, and status of the mountain whitefish in the Big Lost River, 
and to support cooperative conservation of mountain whitefish within 
its historical range in the Big Lost River.

DATES: The finding announced in this document was made on April 6, 
2010.

ADDRESSES: This finding is available on the Internet at https://www.fws.gov/idaho, and also at https://www.regulations.gov at Docket No. 
FWS-R1-ES-2009-0043. 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, Idaho Fish 
and Wildlife Office, 1387 S. Vinnell Way, Room 368, Boise, ID 83709. 
Please submit any new information, materials, comments, or questions 
concerning this finding to the Service at this address.

FOR FURTHER INFORMATION CONTACT: Acting State Supervisor, Idaho Fish 
and Wildlife Office (see ADDRESSES); by telephone at 208-378-5243; and 
by facsimile at 208-378-5262. Persons who use a telecommunications 
device for the deaf (TDD) may call the Federal Information Relay 
Service (FIRS) at 800-877-8339.

SUPPLEMENTARY INFORMATION:

Background

    Section 4(b)(3)(B) of the Endangered Species Act of 1973, as 
amended (Act) (16 U.S.C. 1531 et seq.), requires that, for any petition 
to revise the Federal Lists of Endangered and Threatened Wildlife and 
Plants that contains substantial scientific and commercial information 
indicating that listing the species may be warranted, we make a finding 
within 12 months of the date of receipt of the petition. In this 12-
month finding, we may determine that the petitioned action is either: 
(1) Not warranted, (2) warranted, or (3) warranted, but 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 June 15, 2006, we received a petition from Western Watersheds 
Project to emergency list as endangered or threatened the population of 
mountain whitefish in the Big Lost River, Idaho, as a separate species, 
subspecies, or distinct population segment (DPS) under the Act. The 
petitioner also requested that we designate critical habitat concurrent 
with the listing.
    In an August 21, 2006, letter to the petitioner, we acknowledged 
receipt of the petition and explained that we would not be able to 
address the petition at that time due to other priorities relating to 
court orders and settlement agreements. We further indicated we had 
reviewed the petition and determined an emergency listing was not 
necessary. On October 23, 2007,

[[Page 17353]]

we issued a 90-day finding (72 FR 59983), concluding the petition had 
failed to provide substantial information indicating that listing the 
Big Lost River population of mountain whitefish may be warranted, based 
on a lack of information indicating it may be a listable entity under 
the Act (a species, subspecies, or DPS). On January 25, 2008, Western 
Watersheds Project filed a complaint challenging the negative 90-day 
finding. On March 31, 2009, the United States District Court in Idaho 
found that we had considered information beyond the material in the 
petition in issuing the negative finding, such that we had effectively 
begun to conduct a status review (Western Watersheds Project v. Dirk 
Kempthorne, et al., Case No. CV07-409-S-EJL D. Idaho). The Court 
directed us to proceed directly to a status review and, within 1 year, 
issue a 12-month finding. We published a notice in the Federal Register 
on August 6, 2009 (74 FR 39268) initiating the status review and 
requesting new information for mountain whitefish in the Big Lost 
River, Idaho. The 30-day comment and information period closed on 
September 8, 2009. This notice constitutes the 12-month finding on the 
June 14, 2006, petition to list the mountain whitefish in the Big Lost 
River, Idaho, as endangered or threatened.

Species Information

Species Distribution and Habitat

    Mountain whitefish are members of the family Salmonidae (broadly 
termed ``salmonids'') and are found in rivers and lakes throughout 
mountainous areas of western North America in Canada and the United 
States (Figure 1). In the United States, they occur in the States of 
Washington, Oregon, Idaho, Wyoming, Montana, Colorado, Utah, Nevada, 
and California (NatureServe 2009). Mountain whitefish are relatively 
common and widespread in most river basins in Idaho (AFS 2007, p. 29) 
and, in general, occur in mainstem river reaches that are greater than 
15 meters (m) (49.2 feet (ft)) wide and of low gradient (Maret et al. 
1997, p. 213; Meyer et al. 2009, p. 763). Results of a study by Meyer 
et al. (2009) assessing the environmental factors related to 
distribution, abundance, and life history characteristics of mountain 
whitefish in Idaho show mountain whitefish in southern Idaho are 
abundant, long-lived, and fast growing (at warmer water temperatures) 
until they reach sexual maturity. The authors also speculate that 
mountain whitefish are relatively secure in the upper Snake River 
basin, although little research has been done on the mountain whitefish 
across the range of the species (Meyer et al. 2009, pp. 753, 765).
    Although the majority of populations of mountain whitefish occur in 
riverine environments, some populations are restricted to lakes or 
isolated sink basins. Mountain whitefish in the Big Lost River reside 
in a ``sink'' drainage, which was once part of a large Pleistocene lake 
system that included Lake Terreton (Link 2003, in Van Kirk et al. 2003, 
p. 6). As Lake Terreton waters receded, the Big Lost River and four 
adjacent drainages lost their surface connection to the Snake River, 
resulting in five isolated sink drainages in Idaho. It is estimated 
mountain whitefish became isolated in the Big Lost River approximately 
10,000 years ago (Behnke 2003, cited in Van Kirk et al. 2003, p. 8). 
Other populations of mountain whitefish occur in other sink drainages, 
such as tributaries in the Lahontan Basin in California and Nevada, and 
the Bonneville Basin in Utah. Populations in these basins are similar 
to the population in the Big Lost River in that all are relict 
populations of mountain whitefish that formerly resided in large 
Pleistocene lake systems that are now closed basins.

Distribution and Habitat Within the Big Lost River Basin

    Mountain whitefish in the Big Lost River are physically isolated 
from other whitefish populations within the Snake River basin. The Big 
Lost River originates in the Pioneer, Boulder, Lost River, and White 
Knob mountain ranges and flows down the Big Lost River Valley eastward 
onto the Snake River Plain where it terminates at the Big Lost River 
Sinks (Figure 2). Major tributaries include East Fork, Star Hope Creek, 
Wildhorse Creek, North Fork, Thousand Springs Creek, Warm Springs 
Creek, Alder Creek, Pass Creek, and Antelope Creek. Elevations in this 
area range from 1,459 m (4,787 ft) at the Big Lost River Sinks to 3,859 
m (12,661 ft) at the summit of Borah Peak. The climate of the drainage 
is generally cool and dry. Annual precipitation along the valley floor 
is about 20 centimeters (cm) (7.8 inches (in)), but increases to over 
100 cm (39.4 in) at higher elevations. Vegetation within the basin 
ranges from sagebrush steppe at lower elevations, to coniferous forests 
at mid elevations, to alpine at higher elevations. The drainage is 
comprised primarily of Federal land managed by the U.S. Forest Service 
(USFS; 42 percent), Bureau of Land Management (BLM; 26 percent), and 
Department of Energy (DOE; 15 percent), with lesser amounts of private 
(14 percent) and State (2 percent) lands. The drainage is within 
portions of Butte and Custer Counties and is sparsely populated, with 
agriculture being the dominant land use on private lands. Primary uses 
of Federal land include cattle grazing and recreation (IDFG 2007, p. 
7). Historically, mountain whitefish occupied approximately 346.1 
kilometers (km) (214 miles (mi)) of habitat in the Big Lost River 
(Gamett 2009a, p. 5). Recent studies indicate mountain whitefish 
currently occupy 134.8 km (86.3 mi) of the Big Lost River, with an 
estimated population of 12,639 adult fish (Garren et al. 2009, pp. 5-
6). Although it is lower than suspected historical numbers, the current 
population estimate shows an increase from surveys conducted between 
2002 and 2005, when it was estimated that approximately 2,539 adult 
mountain whitefish occupied 83.3 km (51.8 mi) of habitat in the Big 
Lost River (Gamett et al. 2009, p. 5).

Species Description

    Mountain whitefish can reach about 57 cm (22 in) in length at 
maturity. The general body shape is slender with a somewhat round cross 
section; body coloration is typically silver on the sides, dusky olive 
green or blue on the back; and the belly is a dull white (Simpson and 
Wallace 1982, p. 77). According to Gamett 2009 (personal observations 
and unpublished data, pp. 8-9), mountain whitefish in the Big Lost 
River can be distinguished from mountain whitefish in the nearby 
Pahsimeroi River based on color. Whiteley (2007, pers. comm.) also 
notes a color difference, and suggests that mountain whitefish in the 
Big Lost River may also differ in head and body shape as well. None of 
these suggested differences have been quantified or formally described, 
however, and Gamett (2009, p. 9) notes the need for further research in 
this regard.
    Age of sexual maturity of mountain whitefish varies, with mountain 
whitefish in southern Idaho documented to reach sexual maturity at 2 to 
3 years (Meyer et al. 2009, p. 765), while fish from the Blacks Fork 
River in Utah were reported to reach sexual maturity at 4 years for 
males, and 5 to 7 years for females. The species is relatively long-
lived; one fish in Utah was aged at 12 years (Wydoski 2001, p. 694), 
while the oldest fish recorded in the Meyer et al. study in Idaho was 
estimated to be 24 years old (2009, p. 761). Mountain whitefish spawn 
in the fall, and timing depends on stream temperatures (Simpson and 
Wallace 1982, p. 77; Wydoski 2001, p. 694). Unlike other salmonids, 
mountain whitefish are broadcast spawners,

[[Page 17354]]

meaning no nest or redd is created, and females scatter eggs and the 
male fertilizes them (McGinnis 1984, p. 137). Spawning generally occurs 
at night, with fish broadcasting their eggs and sperm in riffle areas 
over clean gravel. Eggs incubate throughout the winter months, and 
hatching typically occurs in March and April. Migrations associated 
with spawning behavior appear to be highly variable across systems, 
with some populations migrating into tributaries to spawn, while others 
move very little (Northcote and Ennis 1994, p. 350). Upon hatching, fry 
are thought to occupy lateral habitats and low velocity areas. Adult 
habitat is variable, consisting of shallow riffles, moderate runs, and 
deep pools during the summer, but primarily deeper pools in the winter 
(Northcote and Ennis 1994, p. 353).
    Mountain whitefish are thought to be opportunistic bottom feeders, 
consuming whatever is in abundance, including fish eggs during the 
spawning season (McGinnis 1984, p. 137). They are known to actively 
feed on both aquatic and terrestrial insects, but may also eat other 
small fish on occasion (NatureServe 2009).

Taxonomy

    The mountain whitefish in the Big Lost River of Idaho are currently 
recognized as members of the single species Prosopium williamsoni, 
which is considered common and widespread throughout the mountainous 
western United States northward into Canada (Nelson et al. 2004, p. 86; 
ITIS 2009; NatureServe 2009). Although the State of Idaho does not 
consider the mountain whitefish occupying the Big Lost River to be 
either a significant species or a species of concern, they have 
developed a management plan specific to this population of mountain 
whitefish (IDFG 2007, pp. 1-32).

Defining a Species Under the Endangered Species Act

    Our first step in making a 12-month finding is to establish that 
the subject under consideration constitutes a ``species'' as defined 
under section 3(16) of the Act. Section 3(16) defines ``species'' to 
include ``any subspecies of fish or wildlife or plants, and any 
distinct population segment of any species of vertebrate fish or 
wildlife which interbreeds when mature'' (16 U.S.C. 1532(16)). Our 
implementing regulations at 50 CFR 424.11 provide further guidance for 
determining whether a species (as defined in the Act and our 
regulations at 50 CFR 424.02(k)) is eligible for listing under the Act: 
``In determining whether a particular taxon or population is a species 
for the purposes of the Act, the Secretary shall rely on standard 
taxonomic distinctions and the biological expertise of the Department 
and the scientific community concerning the relevant taxonomic group'' 
(50 CFR 424.11(a)).
    As previously discussed, mountain whitefish in the Big Lost River 
are classified taxonomically as Prosopium williamsoni, the same as 
other mountain whitefish across the range of the species. Before 
proceeding further, we must first determine whether the mountain 
whitefish in the Big Lost River are a separate species, subspecies, or 
DPS, and thus constitute a potentially listable entity under the Act.

Evaluation of Mountain Whitefish in the Big Lost River as a Species or 
Subspecies

    The petitioner asked us to list the population of mountain 
whitefish in the Big Lost River, Idaho, as a separate species, 
subspecies, or DPS. As discussed in the ``Taxonomy'' section above, 
mountain whitefish in the Big Lost River of Idaho are currently 
recognized as members of the single species Prosopium williamsoni, 
which is considered common and widespread throughout the mountainous 
western United States northward into Canada (NatureServe 2009). The 
American Fisheries Society and the American Society of Ichthyologists 
and Herpetologists, the scientific authorities with regard to this 
taxonomic group, do not recognize mountain whitefish in the Big Lost 
River as a separate species or subspecies (Nelson et al. 2004, p. 86). 
The Integrated Taxonomic Information System, a database maintained by a 
partnership of Federal agencies to provide scientifically credible 
taxonomic information, similarly does not recognize mountain whitefish 
in the Big Lost River as a separate species or subspecies (ITIS 2009). 
Thus, per our implementing regulations at 50 CFR 424.11, standard 
taxonomic distinctions and the biological expertise of the scientific 
community concerning the relevant taxonomic group, the mountain 
whitefish in the Big Lost River are not recognized as a separate 
species or subspecies of mountain whitefish.
    The petitioner, however, maintained the mountain whitefish in the 
Big Lost River should be protected as a separate species or subspecies 
of whitefish ``because all genetic analyses demonstrate that it is 
genetically unique--so much so that the genetic distance observed 
between Big Lost River mountain whitefish and surrounding populations 
is at least as large as that seen between other subspecies or even 
species.'' We carefully evaluated the petitioner's assertion, which 
relies primarily on the analysis of molecular genetic data. Because of 
the complex and highly technical nature of molecular analysis, we 
consulted with a fisheries genetics expert within the Service to assess 
the potential significance of the genetics information available to us 
regarding mountain whitefish in the Big Lost River. Dr. Donald E. 
Campton, Senior Science Advisor for the U.S. Fish and Wildlife 
Service's Pacific Region Fisheries Resources Division, and former 
President of the Genetics Section of the American Fisheries Society, 
served as our expert on this finding.
    No universally accepted definition of species or subspecies exists. 
In general such classifications are based on multiple lines of evidence 
that are consistent with the hypothesis that the entity in question is 
a separate species or subspecies, including factors such as morphology, 
physiology, behavior, and genetic characteristics (Haig et al. 2006, p. 
1586). In reviewing an entity as a potential species or subspecies, we 
consider as many lines of available, reliable evidence as possible. 
Particularly, in the case of an entity that is being proposed as a new 
taxonomic treatment and that has not been recognized as such by the 
relevant scientific community, we bring our biological expertise to 
bear and require multiple lines of persuasive and credible 
corroborating evidence to support any such change, in accordance with 
our regulations at 50 CFR 424.11(a).
    Information on the genetics of mountain whitefish in the Big Lost 
River of Idaho is available from several recent publications, including 
Whiteley et al. (2006), Campbell and Kozfkay (2006), and Miller (2006). 
In Whiteley et al. (2006), the researchers utilized both allozymes and 
microsatellites to examine the genetic structure of mountain whitefish 
populations throughout the northwestern United States and British 
Columbia, plus two populations from western Alberta. Allozymes are 
forms of enzymes coded for by different alleles at the same genetic 
locus, and can be distinguished by electrophoresis; microsatellites are 
repeating sequences of base pairs in the DNA, and are typically used as 
highly variable genetic markers. Whiteley et al. (2006, p. 2778) found 
that mountain whitefish in this region (all representatives of the 
species Prosopium williamsoni), form three large-scale genetic 
assemblages based on allozyme data and five large-scale genetic 
assemblages based on

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microsatellite data. The Big Lost River population was included within 
the resulting Upper Snake River assemblage (Upper Snake) in both 
scenarios, and is described as the ``most genetically divergent'' site 
in that assemblage. While this is an accurate characterization, 
examination of the data demonstrates that the degree of genetic 
divergence of mountain whitefish in the Big Lost River from other 
populations in the Upper Snake genetic assemblage largely reflects the 
absence of within-population genetic variation in individuals from the 
Big Lost River and is less than the genetic divergence observed between 
the Upper Snake and other major assemblages of mountain whitefish 
(Whiteley et al. 2006, Table 1, pp. 2770-2771). In other words, the 
mountain whitefish in the Big Lost River appear to be divergent largely 
as a result of the lack of genetic diversity exhibited by this 
population relative to other populations, not as the result of any 
unique genetic characteristics. Although the most divergent group 
within the Upper Snake, Whiteley et al. (2006, pp. 2775-2776) found the 
Big Lost River population still clustered within that major genetic 
assemblage.
    This result is consistent with that reported by another researcher 
in her study of mitochondrial DNA in mountain whitefish, detailed 
further below. Miller (2006, p. 30) concludes ``the Big Lost River 
mountain whitefish still group with other populations from the upper 
Snake River Sub-basin.'' These results do not suggest that mountain 
whitefish in the Big Lost River stand out from among all populations of 
mountain whitefish examined as genetically unique or differentiated to 
the point that they would be considered a separate species or 
subspecies. If that were the case, then one would expect the Big Lost 
River mountain whitefish's level of divergence to be greater than the 
level of divergence observed between the major genetic groupings, and 
they would not cluster within a major genetic assemblage.
    The analysis of Whiteley et al. (2006) shows mountain whitefish 
populations that are geographically isolated are relatively more 
distinctive genetically than populations that may experience gene flow 
between them. Although Whiteley et al. (2006, p. 2780) reported little 
evidence of differentiation among sites within major river basins in 
general, they note that the Upper Snake (which includes the Big Lost 
River) and Olympic Peninsula were an exception to this rule, due to the 
natural restrictions on gene flow in these areas. Whiteley et al. 
(2006, p. 2780) identified low levels of within-population genetic 
variation (relatively lower levels of genetic diversity) in several 
physically-isolated populations of mountain whitefish, including not 
only the Big Lost River, but also the Big Wood River, Bull River, and 
Thutade Lake. They also noted a higher degree of genetic 
differentiation in several physically-isolated sites in the region 
associated with the Upper Snake River assemblage; in addition to the 
Big Lost River, this pattern was observed at the Henry's Fork and 
several Bonneville Basin sites (Whiteley et al. 2006, p. 2781).
    Such results are not unexpected; in fact, this condition is exactly 
what would be predicted by basic conservation genetics theory for 
small, isolated populations (Meffe and Carroll 1994, pp. 156-158). 
These isolated populations are relatively genetically divergent 
compared to other populations that experience higher levels of gene 
flow (gene flow or genetic mixing maintains greater levels of genetic 
diversity or heterogeneity in the population). Such a level of 
differentiation does not necessarily suggest a subspecies or species-
level difference; nor does the ability to detect genetic differences 
between populations necessarily equate to meaningful biological 
significance (Hedrick 1999, pp. 316-317). Fish in general, and 
particularly freshwater salmonids, tend to exhibit a high degree of 
genetic structuring (Allendorf and Waples 1996, p. 257; Whiteley et al. 
2006, p. 2783), such that it is not unusual to be able to easily 
distinguish between populations of the same species based on molecular 
genetic differences. Yet, if one were to rely solely on the ability to 
distinguish between fish populations based on genetic differences to 
identify new subspecies or species, as Haig et al. (2006, p. 5, citing 
Mayden 1999) noted, ``every isolated creek and pond could have a unique 
subspecies or species of fish.'' This ability to so finely subdivide 
species based purely on the ability for genetic discrimination between 
them has led the Service, as described above, to require a more 
holistic approach to species or subspecies analysis that builds upon 
multiple lines of evidence, including, where possible, a full suite of 
morphological, physiological, behavioral, and genetic characteristics, 
to support a formerly unrecognized taxonomic distinction.
    The analysis of the genetic relationships of mountain whitefish by 
Whiteley et al. 2006 does not support the contention that mountain 
whitefish of the Big Lost River are distinctive or unique genetically 
when compared to other populations in the Upper Snake River assemblage, 
or when compared to populations within other assemblages of the 
species. Rather, the authors point to a high degree of genetic 
differentiation between many populations of mountain whitefish in the 
Upper Snake due to the topography of the region, and characterize those 
populations as ``more finely subdivided than elsewhere'' (Whiteley et 
al. 2006, p. 2781). The authors also point out that the degree of 
genetic differentiation observed in mountain whitefish among 
tributaries within river basins is less than that observed in 
populations of other salmonids, such as bull trout (Salvelinus 
confluentus) and westslope cutthroat trout (Oncorhynchus clarki lewisi) 
(i.e., bull trout and westslope cutthroat trout show greater levels of 
genetic differentiation between populations within river basins than do 
mountain whitefish) (Whiteley et al. 2006, p. 2783). Despite this high 
degree of genetic structuring, it has not been suggested that each 
individual bull trout or westslope cutthroat trout population be 
considered as a separate species or subspecies; each genetically 
differentiable population of bull trout and westslope cutthroat trout 
is still considered a member of the broader taxon (species or 
subspecies, respectively). If the mountain whitefish in the Big Lost 
River were a separate species or subspecies, based on genetic 
characteristics, one would expect mountain whitefish in the Big Lost 
River to exhibit greater genetic differentiation than populations of 
salmonids that are considered members of the same species or 
subspecies, not less.
    Campbell and Kofzkay (2006) used mitochondrial DNA to assess 
mountain whitefish populations in Idaho, Utah, and Montana, and also 
specifically to evaluate the origin and divergence of mountain 
whitefish in the Big Lost River. Their results support the three major 
genetic assemblages identified by Whiteley et al. (2006), which 
Campbell and Kofzkay (2006, p. 6) describe as the Upper Snake River 
drainage (upstream of Shoshone Falls) and the Bonneville basin; the 
Lower Snake River drainage (downstream of Shoshone Falls) including the 
Pahsimeroi and Salmon Rivers; and the Upper Missouri River. The authors 
note the pairwise divergence estimates between these major genetic 
assemblages of mountain whitefish were very high, ranging from 1.31 to 
4.56 percent (Campbell and Kofzkay 2006, p. 7). For comparison 
purposes, they point out that estimates of mitochondrial DNA sequence 
divergence between two salmonid

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subspecies, the westslope cutthroat trout and Yellowstone cutthroat 
trout (Oncorhynchus clarkia bouvieri), range from 1.5 to 1.9 percent 
(Gyllensten and Wilson 1987, IDGF unpublished data, cited in Campbell 
and Kofzkay 2006, p. 7). The divergence between the large major 
assemblages of mountain whitefish may thus be similar to the degree of 
divergence between recognized subspecies of cutthroat trout.
    However, pairwise divergence estimates for mountain whitefish in 
the Big Lost River are solidly within the range of normal divergence 
for populations of whitefish within the Upper Snake River assemblage 
(Campbell and Kofzkay 2006, Figure 3, p. 8). The percent sequence 
divergence of mountain whitefish from the Big Lost River compared to 
other populations within the Upper Snake River Basin ranges from 0.33 
to 0.49 percent. The levels of sequence divergence between subspecies 
of cutthroat trout (1.4 to 1.9 percent) and between different species 
of trout (rainbow trout (O. mykiss) and cutthroat trout (4.0 to 4.5 
percent) (Campbell and Kozfkay 2006, p. 7) are far higher than that 
observed between mountain whitefish in the Big Lost River and other 
populations within the Upper Snake River assemblage (Campbell and 
Kofzkay 2006, p. 8). According to this study, the genetic distance 
between mountain whitefish in the Big Lost River and surrounding 
populations is far less than that observed between these subspecies or 
species of salmonids. Furthermore, several other populations of 
mountain whitefish examined by Campbell and Kofzkay (2006, Figure 3, p. 
8) exhibited greater levels of divergence from other populations within 
their assemblage than that exhibited by fish from the Big Lost River 
(the Boise River populations in the lower Snake River assemblage, for 
example). Thus, the data of Campbell and Kofzkay (2006) indicate the 
mountain whitefish in the Big Lost River are not particularly 
distinctive or unusual in terms of genetic divergence, when compared to 
other populations of mountain whitefish throughout the range of the 
species.
    Miller (2006) examined the phylogeography of the genus Prosopium in 
western North America, analyzing mitochondrial DNA using the cytochrome 
b (cytb) and NADH dehyrogenase subunit 2 (ND2) sequences. This analysis 
included the mountain whitefish P. williamsoni, and three taxa found 
only in Bear Lake on the Utah-Idaho border: the Bear Lake whitefish (P. 
abyssicola), the Bonneville whitefish (P. spilonotus), and the 
Bonneville cisco (P. gemmifer). Similar to the other researchers, 
Miller reported a high amount of genetic structure for mountain 
whitefish based on drainage basins or sub-basins. Analyses of molecular 
variance demonstrated between 62.5 and 75.8 percent of the total 
genetic variation was found between drainage basins or subbasins 
(Miller 2006, p. 22). Miller's analysis found evidence for multiple 
populations of mountain whitefish that are geographically isolated and 
demonstrate little to no gene flow, including populations in the Hoh 
River, Duchesne River, Big Wood River, Big Lost River, and Coeur 
d'Alene River (Miller 2006, pp. 22-23).
    The nested clade analysis conducted by Miller resulted in somewhat 
different results for the cytb and ND2 sequences. Analysis based on 
cytb resulted in the identification of four major clades of Prosopium: 
(1) A Missouri River basin clade; (2) a Bear Lake Prosopium clade; (3) 
a Columbia River subbasin/lower Snake River subbasin/Lahontan Basin 
clade; and (4) a Bonneville basin/upper Snake River subbasin/Green 
River basin/Bear Lake Prosopium clade (Miller 2006, p. 23). Analysis 
based on ND2 resulted in two major clades: (1) A Columbia River 
subbasin/lower Snake River subbasin/Lahontan basin clade, and (2) a 
Bonneville Basin/upper Snake River subbasin/Green River basin/Missouri 
River basin/Bear Lake Prosopium clade (Miller 2006, p. 23), with the 
Big Lost River and Missouri River populations representing two 
divergent subgroups within this latter clade (Miller 2006, Figs. 16a, 
pp. 130-137, and 16c, pp. 146-149). For both cytb and ND2, she found 
the haplotypes for the Big Lost River (upper Snake River subbasin), the 
Big Wood River (lower Snake River subbasin), and the Hoh River 
(Columbia River subbasin) formed isolated clades (included only 
haplotypes from their own system, and did not contain haplotypes from 
outside of their clades) (Miller 2006, p. 24). Miller concluded that 
these three populations are genetically distinct from other populations 
within their basins due to their relative isolation. With regard to the 
Big Lost River population in particular, however, she concludes, 
``Although distinct from other upper Snake River populations, the Big 
Lost River mountain whitefish still group with other populations from 
the upper Snake River Sub-basin'' (Miller 2006, p. 30). This result is 
consistent with that of Whiteley et al. 2006 (p. 2778); the mountain 
whitefish in the Big Lost River are genetically distinctive within 
their major genetic assemblage, but do not stand out from all other 
populations when considered in the context of the species across its 
range.
    The petitioner offered additional information in support of the 
contention that mountain whitefish in the Big Lost River represent a 
separate species or subspecies; that additional information was a 
reference to an abstract from an oral presentation made at a meeting of 
the Idaho Chapter of the American Fisheries Society (Van Kirk et al. 
2003, p. 13). This abstract, authored by Whiteley and Gamett, refers to 
``the fixation of a unique allele in the Big Lost River population at 
one of the microsatellite loci.'' Data to support this statement were 
not available to us. If we assume that one microsatellite allele has 
become fixed in mountain whitefish occupying the Big Lost River, that 
information does not by itself confer any meaningful genetic 
significance or biological or ecological importance (e.g., as measured 
by morphological, physiological, or behavioral traits) because 
microsatellite alleles are considered selectively neutral, the 
frequencies of which largely reflect random or stochastic processes 
(e.g., genetic drift, population bottlenecks, founder effects, mutation 
rates), rather than selection for traits that confer increased fitness 
(Ashley and Dow 1994, p. 185). Indeed, the total lack of variability 
observed in microsatellites sampled for mountain whitefish in the Big 
Lost River (Whiteley et al. 2006, p. 2775) indicates that this 
population has likely undergone a past population bottleneck relative 
to other populations, with a subsequent loss of genetic variability and 
random fixation (e.g., via drift of a unique [or nearly unique] allele) 
(D. Campton, pers. comm. 2007).
    This conclusion is also supported by the work of Miller, who 
concludes the mountain whitefish in the Big Lost River experienced 
restricted gene flow (2006, p. 25). Under such conditions, genetic 
distance may increase quickly, but is not in and of itself indicative 
of biological significance (Hedrick 1999, pp. 315-316). Genetic 
isolation and a relatively small population size would predictably lead 
to the loss of haplotypes that might otherwise be shared with other 
populations, leading to the ability to distinguish a population as 
``different.'' In other words, it is technically possible to 
differentiate between two such populations on the basis of their 
genetic characteristics. However, this purely technical ability for 
genetic discrimination between populations does not necessarily 
represent any biological or ecological importance. We have no 
information to indicate that the fixation of any single microsatellite 
allele in mountain

[[Page 17357]]

whitefish in the Big Lost River may, in any way, be biologically 
important or significant to the taxon as a whole. Such fixed allelic 
differences between geographically isolated freshwater populations of 
salmonid fishes are not considered uncommon (Allendorf and Waples 1996, 
p. 257). Although these allelic differences may allow for the detection 
of statistically significant differences between populations, and hence 
the ability to discriminate between them on the basis of their genetic 
characteristics, as Hedrick (1999, p. 317) notes, the connection 
between biological and statistical significance may often be weak, and 
great care must be taken in interpreting statistical significance as 
the equivalent of biologically meaningful significance.
    Mountain whitefish in the Big Lost River do possess unique 
mitochondrial DNA haplotypes, but the same is true of almost every 
other mountain whitefish population sampled by Campbell and Kofzkay 
(2006, Table 1, p. 6) and Miller (2006, Table 3, pp. 51-56, and Table 
4, pp. 57-63). The majority of surveyed mountain whitefish populations 
had unique mitochondrial DNA haplotypes, as does the population in the 
Big Lost River, and some populations had several. The possession of a 
population-specific haplotype is, therefore, not unique to the mountain 
whitefish in the Big Lost River. In addition, the genetic divergence of 
mountain whitefish in the Big Lost River is not necessarily greater 
than that observed in other populations. For example, based on the data 
of Campbell and Kofzkay (2006, Figure 3, p. 8) and Miller (2006, Figure 
16, pp. 130-157), the divergence among haplotypes between fish in the 
Big Lost River and other populations in the Upper Snake River is 
approximately three times less than the degree of divergence observed 
among individual mountain whitefish collected from a single population 
in the Boise River.
    In our review of the best available information regarding the 
degree of genetic divergence of mountain whitefish in the Big Lost 
River relative to other populations of whitefish, we have determined 
that many - if not most - populations of mountain whitefish sampled by 
Campbell and Kozfkay (2006, p. 6) and Miller (2006, pp. 51-63) can be 
said to be genetically different relative to other populations of the 
species. Most mitochondrial DNA haplotypes occur in only one population 
and are not shared between populations, clearly indicating the lack of 
gene flow among most populations (Campbell and Kofzkay 2006, Table 1, 
p. 6; Miller 2006, Table 3, pp. 51-56, and Table 4, pp. 57-63). In 
addition, substantially greater mitochondrial DNA nucleotide diversity 
exists among individual fish within some populations of mountain 
whitefish, than exists between mountain whitefish in the Big Lost River 
and other populations in the Upper Snake River (Campbell and Kofzkay 
2006, Figure 3, p. 8; Miller 2006, Figure 16, pp. 130-157). Genetic 
analyses by both Whiteley et al. (2006, pp. 2775-2776) and Miller 
(2006, p. 30) determined that mountain whitefish in the Big Lost River 
cluster within the Upper Snake genetic subgroup of Prosopium 
williamsoni. Based on the best available scientific information, we 
conclude the evidence is not sufficient to support recognition of the 
mountain whitefish in the Big Lost River as a separate species or 
subspecies based on the genetic characteristics of the population 
relative to all other populations of the species P. williamsoni.
    As we noted earlier, in evaluating whether an entity may 
potentially represent a heretofore unrecognized species or subspecies, 
it is important to consider multiple lines of evidence. Haig et al. 
(2006, p. 8) argue that higher levels of confidence can be obtained in 
classifications based on the concurrence of multiple morphological, 
molecular, ecological, behavioral, and physiological characters. We 
therefore considered whether any other characteristics of mountain 
whitefish in the Big Lost River offer any credible support for the 
argument that they may be a separate species or subspecies.
    The information available to us suggests mountain whitefish in the 
Big Lost River may exhibit differences in coloration or morphology. 
This suggestion is based on the personal observations of two 
researchers, Andrew Whiteley and Bart Gamett. Dr. Whiteley suggested 
that mountain whitefish from the Big Lost River may differ in color and 
form, possibly having shorter heads and a different body shape, but 
stated that these traits have not been quantified and were based only 
on his personal observations (A. Whiteley 2007a, pers. comm.). Mr. 
Gamett (2009b, pp. 8-9) also noted that mountain whitefish from the Big 
Lost River can be readily distinguished from specimens of mountain 
whitefish found in other drainages (e.g., Pahsimeroi River) based on 
color; however, this has not been formally described, and is based on 
personal opinion. Gamett (2009b, p. 9) noted that further research is 
needed to address this question.
    Although mountain whitefish in the Big Lost River may possibly look 
different, we have no evidence before us to suggest that any 
differences in color or morphology that may exist are anything other 
than natural phenotypic variation that is often observed in different 
populations of fish. Natural variation in characteristics such as body 
shape in fish is commonly attributable to environmental factors, such 
as water temperature during development (e.g., Barlow 1961, pp. 105-
106). Additionally, many fish exhibit a considerable degree of 
intraspecific (within the species) variation in morphology, which has 
been experimentally demonstrated to be the result of phenotypic 
plasticity in response to the environment, rather than a heritable 
response to selection (e.g., Mittelbach et al. 1999, pp. 111, 126). 
Head depth is a common plastic trait in fish related to diet (e.g., Day 
et al. 1994, pp. 1723, 1730). We have no information to suggest that 
any apparent differences in morphology or coloration of the mountain 
whitefish in the Big Lost River, which have never been quantified or 
formally described, are in any way biologically meaningful such that 
they might represent possible differentiation to the degree that 
subspecies or species recognition might be warranted--that is, whether 
they might possibly be associated with some fitness advantage or 
adaptation specific to this population, as opposed to simple local 
variation in phenotypic traits.
    It has been suggested that the mountain whitefish in the Big Lost 
River are more genetically divergent than currently recognized species 
of Prosopium endemic to Bear Lake (Whiteley 2007b, pers. comm.). In her 
examination of the three species of Prosopium endemic to Bear Lake (P. 
abyssicola, P. gemmifer, and P. spilonotus), Miller (2006, pp. 31-32) 
found the mitochondrial DNA data failed to break into discrete clades 
of their respective species, possibly indicative of ongoing adaptive 
radiation (i.e., they are still undergoing the process of speciation), 
ongoing hybridization, or other factors. In this case, although the 
genetic information does not provide a clear distinction between these 
three groups, other multiple lines of evidence potentially support the 
taxonomic distinction between these species, including differences in 
spawning times, scale counts, and morphology (Miller 2006 and 
references therein, pp. 2-3, 34). Miller notes that although the three 
Bear Lake species are not genetically differentiable, the 
``morphological, ecological, and behavioral differences are real'' 
(Miller 2006, p. 32). However, she also points out that this lack of 
congruence with the genetic information

[[Page 17358]]

does raise some questions regarding the current classification of these 
species (Miller 2006, p. 35), further reinforcing the point that 
stronger taxonomic distinctions can be made based on multiple lines of 
consistent supporting evidence.
    By contrast, although mountain whitefish in the Big Lost River may 
show a greater degree of genetic differentiation from other groups than 
that observed in the Bear Lake Prosopium, we note that any potentially 
corroborating morphological, ecological, behavioral, or physiological 
characteristics that might serve as supporting evidence of meaningful 
phenotypic divergence, such as that used in identifying the three 
species of Bear Lake Prosopium, are lacking for mountain whitefish in 
the Big Lost River. Most populations of mountain whitefish exhibit a 
high degree of geographical genetic differentiation throughout their 
range (Campbell and Kofzkay 2006, Figure 3, p. 8; Whiteley et al. 2006, 
p. 2781), and several of them show a greater degree of genetic 
differentiation than that exhibited between the three species of Bear 
Lake Prosopium (Miller 2006, Figure 16, pp. 130-157). However, in the 
absence of any reliable corresponding evidence indicative of local 
adaptation or phenotypic divergence, we believe there is insufficient 
support for the recognition of any such population as a new species or 
subspecies based on this genetic information. Thus we do not find the 
greater genetic divergence observed in mountain whitefish in the Big 
Lost River relative to that observed between the Bear Lake Prosopium 
persuasive evidence that mountain whitefish in the Big Lost River 
should be considered a species or subspecies.
    In summary, mountain whitefish occurring in the Big Lost River are 
not currently recognized by the relevant taxonomic authorities as a 
species or subspecies (Nelson et al. 2004, p. 86; ITIS 2009; 
NatureServe 2009), and our evaluation of the best available scientific 
and commercial data does not indicate that mountain whitefish in the 
Big Lost River represent a distinct species or subspecies relative to 
other populations of Prosopium williamsoni. Available evidence 
indicates there is a high degree of genetic structuring between many 
populations of mountain whitefish, and particularly those in the Upper 
Snake, as is frequently observed between populations of other 
freshwater salmonids (Allendorf and Waples 1996, p. 257; Miller 2006, 
p. 25; Whiteley et al. 2006, pp. 2781, 2783). Modern molecular 
techniques allow virtually every population to be distinguished from 
one another, and almost every population of mountain whitefish surveyed 
had at least one unique haplotype. Thus every population of mountain 
whitefish sampled so far could be considered genetically ``distinct,'' 
including the mountain whitefish in the Big Lost River. As explained 
above, however, the genetic data before us do not indicate that the 
mountain whitefish in the Big Lost River are biologically unique or 
unusual compared to other populations of the species, so as to warrant 
consideration as a separate species or subspecies.
    Furthermore, in reviewing all available information, we found no 
substantiated evidence of ecological, morphological, physiological, 
behavioral, or other characteristics that would indicate any adaptive 
divergence or patterns of adaptation have taken place in mountain 
whitefish occurring in the Big Lost River, and that might be considered 
additional evidence of a potentially distinct species or subspecies. We 
therefore conclude, based on all of the best available scientific and 
commercial data, that consideration of mountain whitefish in the Big 
Lost River as a separate species or subspecies is not warranted at this 
time.

Evaluation of Mountain Whitefish in the Big Lost River as a Distinct 
Population Segment

    To interpret and implement the distinct vertebrate population 
segment (DPS) provisions of the Act and Congressional guidance, we, in 
conjunction with the National Marine Fisheries Service (now the 
National Oceanic and Atmospheric Administration--Fisheries), published 
the Policy Regarding the Recognition of Distinct Vertebrate Population 
Segments (DPS Policy) in the Federal Register on February 7, 1996 (61 
FR 4722). Under the DPS policy, two basic elements are considered in 
the decision regarding the establishment of a population of a 
vertebrate species as a possible DPS. We must first determine whether 
the population qualifies as a DPS; this requires a finding that the 
population is both: (1) Discrete in relation to the remainder of the 
species to which it belongs; and (2) biologically and ecologically 
significant to the species to which it belongs. If the population meets 
the first two criteria under the DPS policy, we then proceed to the 
third element in the process, which is to evaluate the population 
segment's conservation status in relation to the Act's standards for 
listing as an endangered or threatened species. These three elements 
are applied similarly for additions to or removals from the Federal 
Lists of Endangered and Threatened Wildlife and Plants.
    In accordance with our DPS Policy, we detail our analysis of 
whether a vertebrate population segment under consideration for listing 
may qualify as a DPS. As described above, we first evaluate the 
population segment's discreteness from the remainder of the species to 
which it belongs. Under the DPS policy, a population segment of a 
vertebrate taxon may be considered discrete if it satisfies either one 
of the following conditions:
     (1) It is markedly separated from other populations of the same 
taxon as a consequence of physical, physiological, ecological, or 
behavioral factors. Quantitative measures of genetic or morphological 
discontinuity may provide evidence of this separation.
     (2) It is delimited by international governmental boundaries 
within which differences in control of exploitation, management of 
habitat, conservation status, or regulatory mechanisms exist that are 
significant in light of section 4(a)(1)(D) of the Act.
    If we determine that a vertebrate population segment is discrete 
under one or more of the conditions described in the Service's DPS 
policy, we then consider its biological and ecological significance to 
the larger taxon to which it belongs, in light of Congressional 
guidance (see Senate Report 151, 96th Congress, 1st Session) that the 
authority to list DPSes be used ``sparingly'' while encouraging the 
conservation of genetic diversity. In making this determination, we 
consider available scientific evidence of the discrete population 
segment's importance to the taxon to which it belongs. Since precise 
circumstances are likely to vary considerably from case to case, the 
DPS policy does not describe all the classes of information that might 
be used in determining the biological and ecological importance of a 
discrete population. However, the DPS policy describes four possible 
classes of information that provide evidence of a population segment's 
biological and ecological importance to the taxon to which it belongs. 
As specified in the DPS policy (61 FR 4722), this consideration of the 
population segment's significance may include, but is not limited to, 
the following:
    (1) Persistence of the discrete population segment in an ecological 
setting unusual or unique to the taxon;
    (2) Evidence that loss of the discrete population segment would 
result in a significant gap in the range of a taxon;
    (3) Evidence that the discrete population segment represents the 
only

[[Page 17359]]

surviving natural occurrence of a taxon that may be more abundant 
elsewhere as an introduced population outside its historic range; or
     (4) Evidence that the discrete population segment differs markedly 
from other populations of the species in its genetic characteristics.
    A population segment needs to satisfy only one of these conditions 
to be considered significant. Furthermore, other information may be 
used as appropriate to provide evidence for significance.
Discreteness
    Our DPS policy states that a population segment of a vertebrate 
species may be considered discrete if it is markedly separated from 
other populations of the same taxon as a consequence of physical, 
physiological, ecological, or behavioral factors. We find that mountain 
whitefish in the Big Lost River are discrete, since they occur in a 
closed basin lacking a surface connection to any major river system, 
and are therefore physically separated from the remainder of the 
populations in the taxon. We therefore conclude that mountain whitefish 
in the Big Lost River satisfy the discreteness criterion of the DPS 
policy.
Significance
    Having determined that mountain whitefish in the Big Lost River 
meet the discreteness criterion, our DPS policy directs us to next 
consider available scientific evidence of the biological and ecological 
importance of this discrete population to the remainder of the species 
to which it belongs. In this case, we evaluate the biological and 
ecological significance of the mountain whitefish in the Big Lost River 
relative to mountain whitefish throughout the remainder of their range 
in the western United States and Canada. A discrete population is 
considered significant under the DPS policy if it meets one of four of 
the elements identified in the policy under significance, or can 
otherwise be reasonably justified as being significant. Here we 
evaluate the four potential factors suggested by our DPS policy in 
evaluating significance.

(1) Persistence of the Discrete Population Segment in an Ecological 
Setting Unusual or Unique to the Taxon

    Mountain whitefish in the Big Lost River are found in a closed 
surface drainage basin. However, as noted earlier, mountain whitefish 
also occur in isolated populations in sink drainages in the Bonneville 
Basin in Utah and the Lahontan Basin in California and Nevada. In 
addition, mountain whitefish also occur in other geographically 
isolated settings, such as above barrier waterfalls (e.g., Big Wood 
River, Bull River, Thutade Lake, Henry's Fork; Whiteley et al. 2006, 
pp. 2780-2781) or above saltwater barriers to dispersal, as on the 
Olympic Peninsula (Whiteley et al. 2006, p. 2781). Therefore, the mere 
fact that these mountain whitefish occupy a physically isolated 
drainage is not in and of itself unique, unusual, or significant to the 
species as a whole. Although we acknowledge that Miller (2006, p. 29) 
describes the Big Lost River as the most unique drainage of the upper 
Snake River subbasin due to its geological history, we note that this 
reference is comparing the drainage only within the context of the 
subbasin in which it occurs, and not to the entire range of mountain 
whitefish. Miller (2006, p. 2) points out that members of the genus 
Prosopium in western North America ``occupy discrete drainage basins 
most of which have complex geological histories.'' Residence in a 
discrete drainage basin with a complex geological history therefore 
appears to be a general characteristic of the genus.
    We have no information indicating that the geological history of 
the Big Lost River drainage, even if considered unique or unusual, has 
in any way contributed to a unique or unusual ecological setting, such 
that the whitefish occurring therein are biologically or ecologically 
significant to the species as a whole. As noted above, there are other 
populations of mountain whitefish in closed ``sink'' drainages within 
the range of the species. We have no information indicating that the 
Big Lost River drainage is ecologically unusual or unique in any other 
way (for example, in terms of unique or unusual prey species, community 
composition, water chemistry, pathogens, or substrate), apart from its 
geographic setting, that may serve as an indicator of the biological or 
ecological importance of the population of mountain whitefish found 
there in relation to the species as a whole. The one exception is a 
suggestion that the Big Lost River may be ecologically unusual because 
historically it lacked other large fish species, such as trout; we 
discuss this suggestion below.
    Gamett (2009b, p. 8) suggests that the Big Lost River may be 
unusual due to the fact that other than mountain whitefish, the only 
other large fish native to the river are sculpin, and all other 
mountain whitefish have evolved in the presence of other large fish 
such as trout and suckers. He states that all other fish species, 
including several species of trout, were not introduced into the Big 
Lost River until the arrival of the first permanent settlers in the 
late 1800s (Gamett 2009a, pp. 1, 8). We carefully considered the 
potential ecological or biological significance of this information. If 
there were some evidence that in the absence of trout or other large 
fish, mountain whitefish in the Big Lost River had somehow become 
specialized or otherwise adapted to this particular ecological 
condition in a way that set them apart from the remainder of the 
species, this may be of potential biological or ecological importance. 
There is no information to suggest that mountain whitefish in the Big 
Lost River became specialized or adapted in this manner. Several 
species of trout were introduced to the Big Lost River more than 100 
years ago, with no apparent effect--behavioral, morphological, or 
otherwise--on the mountain whitefish population. Mountain whitefish in 
the Big Lost River have shown none of the responses typical of a native 
species responding to an unfamiliar invasive species, such as niche 
displacement or competitive exclusion (Mooney and Cleland 2001, pp. 
5446-5451).
    We found no information to suggest that mountain whitefish in the 
Big Lost River had become so specialized following their isolation from 
the remainder of the taxon that they are now incapable of coexisting 
with trout. Studies have shown no evidence of competition between 
nonnative fish and mountain whitefish, and it is considered unlikely 
that competition has negatively affected mountain whitefish in the Big 
Lost River, since declines in this mountain whitefish population were 
only reported relatively recently, and were not observed subsequent to 
the introduction of trout over 100 years ago (IDFG 2007a, p. 22). 
Therefore, although the information that mountain whitefish in the Big 
Lost River were isolated from trout and other potentially predatory or 
competitive fishes up until approximately 100 years ago is possibly of 
some biological interest, we have no evidence that it represents any 
ecological significance of the setting, or has resulted in any unique 
or unusual adaptations or trait shifts in the mountain whitefish, such 
that the population of mountain whitefish in the Big Lost River would 
be considered biologically or ecologically significant to the species 
throughout its range.
    On the basis of an evaluation of the best available scientific 
information, we have determined that the Big Lost River does not 
represent an ecological setting that is unusual or unique for mountain 
whitefish relative to the taxon's range in western North America. Other

[[Page 17360]]

populations of mountain whitefish occur in closed drainage basins 
within the range of the species and other populations of mountain 
whitefish occur in settings that are physically or geographically 
isolated (and therefore reproductively isolated) from the remainder of 
the taxon. Although mountain whitefish may have lived in the Big Lost 
River since the estimated time of their physical isolation some 10,000 
years ago in the absence of trout and other large fish, we have no 
evidence that this past ecological condition is of any biological or 
ecological significance. There is no evidence that the introduction of 
multiple species of trout to the Big Lost River over 100 years ago had 
any effect on the mountain whitefish population, suggesting that their 
previous absence had not altered the mountain whitefish's behavior or 
ecology in any biologically significant ways, or resulted in any 
locally adapted traits. None of the information available to us 
indicates that the setting of the Big Lost River is unique or unusual 
in any other aspect of its ecology; we have no information suggesting 
the Big Lost River is unusual or unique in any of its ecological 
characteristics such as water chemistry, temperature, substrate, 
pathogens, or prey species utilized. We conclude that mountain 
whitefish occurring in the Big Lost River do not occupy an unusual or 
unique ecological setting such as to be biologically or ecologically 
significant to the remainder of the taxon to which they belong. We 
therefore conclude that mountain whitefish in the Big Lost River do not 
meet the significance criterion of the DPS policy based on this factor.

 (2) Evidence That Loss of the Discrete Population Segment Would Result 
in a Significant Gap in the Range of a Taxon

    Mountain whitefish are found throughout mountainous areas of 
western North America in the United States and Canada. They are 
considered common and widely distributed throughout the upper Snake and 
Missouri rivers to the east and northeast, the lower Snake and Columbia 
rivers to the west and northwest, and the Bonneville and Lahontan 
basins to the south and southwest. In southern Idaho alone, the 
population of mountain whitefish is estimated to be 4.7  
1.8 million, based on a study of 119,453 km (74,225 mi) of stream 
surveys (Meyer et al. 2009, p. 760). The population of mountain 
whitefish in the Big Lost River is estimated to be 12,639 adults, 
occupying 135 km (83 mi) of stream (Garren et al. 2009, p. 6). The 
fraction of the population and its range represented by the mountain 
whitefish in the Big Lost River is very small when considered relative 
to the remainder of the species' range in southern Idaho. When compared 
to the range of mountain whitefish throughout western North America, we 
find that the gap in the range that would result from the loss of the 
single population of mountain whitefish in the Big Lost River of Idaho 
would not be significant, because it is so very small. We therefore 
conclude that mountain whitefish in the Big Lost River do not meet the 
significance criterion of the DPS policy based on this factor.

(3) Evidence That the Discrete Population Segment Represents the Only 
Surviving Natural Occurrence of a Taxon That May Be More Abundant 
Elsewhere as an Introduced Population Outside Its Historical Range

    This criterion does not apply to mountain whitefish in the Big Lost 
River because it is not a population segment representing the only 
surviving natural occurrence of the taxon that may be more abundant 
elsewhere as an introduced population outside its historical range. We 
therefore conclude that mountain whitefish in the Big Lost River do not 
meet the significance criterion of the DPS policy based on this factor.

(4) Evidence That the Discrete Population Segment Differs Markedly from 
Other Populations of the Species in Its Genetic Characteristics

    We evaluated information available to us regarding the genetic 
characteristics of mountain whitefish in the Big Lost River in our 
evaluation of this population as a potentially separate species or 
subspecies (see ``Evaluation of Mountain Whitefish in the Big Lost 
River as a Species or Subspecies'' above). Our conclusions from this 
evaluation apply here as well, and we include the above discussion 
under this factor by reference, although under the DPS policy we 
measure the evidence against a slightly different standard (potential 
biological and ecological significance to the species as a whole, as 
reflected by marked differences in its genetic characteristics). Our 
evaluation of the best available scientific information, as detailed 
above, does not support the contention that the genetic characteristics 
of mountain whitefish in the Big Lost River differ markedly from those 
of other populations relative to levels of divergence among other 
populations of mountain whitefish. On the contrary, the information 
indicates that the genetic distance observed between mountain whitefish 
in the Big Lost River and surrounding populations is less than that 
observed between other species or subspecies of salmonids to which it 
has been compared (Campbell and Kozfkay 2006, p. 7), and is also less 
than that observed between individual fish within some populations of 
mountain whitefish in other areas (Miller 2006, Figs. 15 and 16). As 
detailed above, the evidence indicates the degree of genetic 
differentiation between mountain whitefish in the Big Lost River and 
surrounding populations is no greater than that observed between many 
other populations of mountain whitefish throughout the range of the 
species (Campbell and Kofzkay 2006, Figure 3, p. 8; Miller 2006, pp. 
27-35; Whiteley et al. 2006, p. 2781). When measuring this evidence 
against the DPS standard, we looked for evidence of marked 
differentiation of mountain whitefish in the Big Lost River when 
compared to other populations of mountain whitefish throughout the 
range of the species. We conclude the degree of genetic divergence 
observed in this population does not rise to the level of significance 
to the taxon as a whole.
    As noted above, the most recent genetic work (Miller 2006, pp. 27-
35; Whiteley et al. 2006, pp. 2780-2781) indicates there are several 
physically isolated populations of mountain whitefish that, as expected 
under a scenario of reduced gene flow, show some divergence from their 
presumed common populations of origin. Furthermore, the research 
demonstrates that most populations of mountain whitefish sampled have 
diverged to the point of possessing unique haplotypes, and other 
populations of mountain whitefish exhibit a greater degree of genetic 
divergence than observed in mountain whitefish from the Big Lost River 
(Campbell and Kozfkay 2006, p. 7). Mountain w