[Federal Register: February 21, 2006 (Volume 71, Number 34)]
[Proposed Rules]               
[Page 8818-8831]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]



Fish and Wildlife Service

50 CFR Part 17

Endangered and Threatened Wildlife and Plants; 12-Month Finding 
for a Petition To List the Yellowstone Cutthroat Trout as Threatened

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of a 12-month petition finding.


SUMMARY: We, the U.S. Fish and Wildlife Service (USFWS), announce our 
12-month finding for a petition to list the Yellowstone cutthroat trout 
(YCT) (Oncorhynchus clarkii bouvieri) as a threatened species 
throughout its range in the United States, pursuant to the Endangered 
Species Act of 1973, as amended. After a thorough review of all 
available scientific and commercial information, we find that listing 
the YCT as either threatened or endangered is not warranted at this 
time. We ask the public to continue to submit to us any new information 
that becomes available concerning the status of or threats to the 
subspecies. This information will help us to monitor and encourage the 
ongoing conservation of this subspecies.

DATES: The finding in this document was made on February 14, 2006.

ADDRESSES: Data, information, comments, or questions regarding this 
notice should be sent to U.S. Fish and Wildlife Service, 780 Creston 
Hatchery Road, Kalispell, Montana 59901. The complete administrative 
file for this finding is available for inspection, by appointment and 
during normal business hours, at the above address. The petition 
finding, the status review for YCT, related Federal Register notices, 
the Court Order, and other pertinent information, may be obtained on 
line at http://frwebgate.access.gpo.gov/cgi-bin/leaving.cgi?from=leavingFR.html&log=linklog&to=http://mountain-prairie.fws.gov/endspp/fish/YCT/.

FOR FURTHER INFORMATION CONTACT: The Montana Ecological Services Field 
Office (see ADDRESSES), by telephone at (406) 758-6872, by facsimile at 
(406) 758-6877, or by electronic mail at fw6_yellowstonecut@fws.gov.



    Section 4(b)(3)(B) of the Endangered Species Act of 1973, as 
amended (ESA) (16 U.S.C. 1531 et seq.), requires that, for any petition 
to revise the List of Endangered and Threatened Species that contains 
substantial scientific and commercial information that listing may be 
warranted, we make a finding within 12 months of the date of receipt of 
the petition on whether the petitioned action is (a) not warranted, (b) 
warranted, or (c) warranted but the immediate proposal of a regulation 
implementing the petitioned action is precluded by other pending 
proposals to determine whether any species is threatened or endangered, 
and expeditious progress is being made to add or remove qualified 
species from the List of Endangered and Threatened Species. Section 
4(b)(3)(C) of the ESA requires that a petition for which the requested 
action is found to be warranted but precluded be treated as though 
resubmitted on the date of such finding, i.e., requiring a subsequent 
finding to be made within 12 months. Such 12-month findings must be 
published in the Federal Register.
    On August 18, 1998, we received a petition dated August 14, 1998, 
to list the YCT as threatened, under the ESA, where it presently occurs 
throughout its historic range. Petitioners were Biodiversity Legal 
Foundation, the Alliance for the Wild Rockies, the Montana Ecosystems 
Defense Council, and George Wuerthner.

Biology and Distribution

    The YCT is 1 of about 13 named subspecies of cutthroat trout native 
to interior regions of western North America (Behnke 1992, 2002). 
Cutthroat trout owe their common name to the distinctive red or orange 
slash mark that occurs just below both sides of the lower jaw. Aside 
from distribution, morphological differences, particularly external 
spotting patterns, may distinguish the various subspecies of cutthroat 
trout (Behnke 1992). Adult YCT typically exhibit bright yellow, orange, 
and red colors on their flanks and opercles, especially among males 
during the spawning season. Characteristics of YCT that may be useful 
in distinguishing this fish from the other subspecies of cutthroat 
trout include a pattern of irregularly shaped spots on the body, with 
few spots below the lateral line except near the tail; a unique number 
of chromosomes; and other genetic and morphological traits that appear 
to reflect a distinct evolutionary lineage (Behnke 1992).
    Also among those 13 cutthroat trout subspecies is the fine-spotted 
Snake River cutthroat trout (which Behnke [1992] referred to as 
Oncorhynchus clarkii spp., but more recently referred to as 
Oncorhynchus clarkii behnkei [Behnke 2002]). The natural range of the 
fine-spotted Snake River cutthroat trout is principally in the western 
portion of Wyoming and southeastern Idaho, almost entirely surrounded 
by that of O. c. bouvieri (Behnke 1992). In their petition, the 
petitioners considered the fine-spotted Snake River cutthroat trout a 
morphological form (or morphotype) of YCT. Biochemical-genetic studies 
have revealed very little genetic difference between the large-spotted 
form of YCT and the fine-spotted cutthroat trout of the Snake River 
basin (most recently, Mitton et al. 2006 in review, Novak et al. 2005). 
As the common names indicate, the large-spotted YCT and fine-spotted 
cutthroat trout are typically separable based primarily on the basis of 
the sizes and patterns of spots on the sides of the body. The large-
spotted YCT has pronounced, medium to large spots that are round in 
outline and moderate in number, whereas the spots of the fine-spotted 
cutthroat trout are the smallest of any native trout in western North 
America and so profuse they resemble ``a heavy sprinkling of ground 
pepper'' (Behnke 1992). However, in areas of natural geographic 
overlap, intergrades of the two forms with intermediate spotting 
patterns are common (Novak et al. 2005).
    For purposes of this review, we use the name YCT to represent both 
of the closely related putative subspecies (Oncorhynchus clarkii 
bouvieri and Oncorhynchus clarkii behnkei) and they are considered a 
single entity (as petitioned) in our status review (USFWS 2006). We 
refer to them collectively as YCT throughout this document.
    Although not specifically documented with historical data, the 
recent historic range of YCT is thought to have included waters of the 
Snake River drainage (Columbia River basin) upstream from Shoshone 
Falls, Idaho (River Mile 614.7), and those of the Yellowstone River 
drainage (Missouri River basin) upstream from and including the Tongue 
River, in eastern Montana (Behnke 1992). Historic range of YCT in the 
Yellowstone River drainage thus includes large regions of northwest 
Wyoming and southcentral Montana. Historic range in the Snake River 
drainage includes large regions of the western portion of Wyoming, 
southeast Idaho, and small parts of the northwest corner of Utah and 
northeast corner of Nevada (Behnke 1992, Novak

[[Page 8819]]

et al. 2005). The transcontinental divide range of YCT in Montana and 
Wyoming likely resulted from headwater connection. The range of YCT may 
have once extended further downstream, but probably became isolated in 
the headwaters of the Snake River following creation of Shoshone Falls 
(between 30,000 and 60,000 years ago). Today, various YCT stocks remain 
in the headwaters of the Snake and Yellowstone River drainages in 
Montana, Wyoming, Idaho, Utah, and Nevada.
    The distribution of YCT occurs in 40 watersheds that can be 
delineated by 4th code Hydrologic Unit Code (HUC) boundaries. Those 
HUCs generally equate to named watersheds. In this 12-month finding, 
the term HUC and the word watershed are used more or less 
interchangeably. Twenty-two of those HUCs are in the headwaters of the 
Yellowstone River basin and 18 are in the Snake River basin headwaters. 
Because the status of native fish species can often vary substantially 
from drainage to drainage, based on the presence and degree of threats 
and other factors, we believe it is appropriate to treat these 40 
watersheds as separate but related entities in order to evaluate the 
array of threats and status of the species. We will follow that 
approach to describe many of the threats for YCT.
    May et al. (2003) defined a conservation population, per the State 
position paper on Genetic Considerations Associated with Cutthroat 
Trout Management (Utah Division of Wildlife Resources 2000), as one 
that is either genetically unaltered (i.e., core population) or one 
that may be slightly introgressed due to past hybridization (typically 
less than 10 percent) and having attributes worthy of conservation. 
Hybridization is an important concern for YCT populations. For 
hybridization to result in an introgressed population, it requires that 
the nonnative species be introduced into or invade the YCT habitat, 
that the two species then interbreed (i.e., ``hybridize''), and that 
the resulting hybrids themselves survive and reproduce. If the F1 
hybrids backcross with one or both of the parental species, genetic 
introgression occurs. 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.
    We have adopted the States' standards and consider all core and 
conservation populations, as defined under these standards and as 
described by May et al. (2003) to be YCT for purposes of this 12-month 
finding. Because the categories are nested, the term conservation 
population includes the core populations, and we refer to the 
collective as conservation populations in the remainder of this 
document. Those conservation populations collectively occupied about 84 
percent of the total habitat occupied by YCT (the rest are sport fish 
populations that are not considered YCT conservation populations).
    The YCT status assessment report (May et al. 2003), identified 
10,220 kilometers (km) (6,352 miles [mi]) of stream habitat occupied by 
195 separate YCT conservation populations. May et al. (2003) indicated, 
based on professional judgment which was used to produce an estimate of 
potentially suitable habitat, that YCT historically occupied about 
28,014 km (17,407 mi) of habitat (mostly stream, but including some 
lakes) in five States. More details of the estimated current and 
historic distribution are found in the status review accompanying this 
finding (USFWS 2006).

Previous Federal Actions

    On February 23, 2001, we published a 90-day finding (66 FR 11244) 
which found that the petition to list the YCT failed to present 
substantial information indicating that listing the YCT may be 
warranted. A complaint was filed in the U.S. District Court for the 
District of Colorado on January 20, 2004, on the conclusion of this 90-
day finding. On December 17, 2004, the District Court of Colorado 
(Judge Figa) ruled in favor of the plaintiffs and ordered the USFWS to 
produce a 12-month finding for YCT. On February 14, 2005, the Court 
clarified the order and attached a February 14, 2006, due date for the 
USFWS to complete the 12-month finding. We published a notice reopening 
the comment period for 60 days on August 31, 2005 (September 1, 2005; 
70 FR 52059). The comment period closed on October 31, 2005.

Summary of Factors Affecting the Species

    Section 4 of the ESA (16 U.S.C. 1533), and implementing regulations 
at 50 CFR part 424, set forth procedures for adding species to the 
Federal List of Endangered and Threatened Species. In making this 
finding, information regarding the status and threats to this species 
in relation to the five factors provided in section 4(a)(1) of the ESA 
is summarized below.
    We examined each of these factors as they relate to the current 
distribution of YCT. In response to our 2000 and 2005 Federal Register 
notices, we received comments and information on YCT from several State 
fish and wildlife agencies, the U.S. Forest Service (USFS), private 
citizens and organizations, the Shoshone-Bannock Tribes, and other 
entities. Among the materials that we received, the most important was 
a status assessment report for YCT (May et al. 2003). The May et al. 
(2003) status assessment was a comprehensive document covering the 
entire range of the YCT, coauthored by the USFS in conjunction with 
fish and wildlife agencies of the States of Idaho, Montana, Wyoming, 
Utah, and Nevada.
    The YCT status assessment report (May et al. 2003) and the 
comprehensive database that is the report's basis, along with other 
supplemental submissions from the agencies and commentors, presented to 
us the best scientific and commercial information available that 
describes the present-day rangewide status of YCT in the United States. 
To compile the information in the status report (May et al. 2003), 43 
professional fishery biologists from 10 State, Federal, and Tribal 
agencies and private firms met at 5 State workshops held across the 
range of YCT, in 2000. At the workshops, the biologists submitted 
essential information on the YCT in their particular geographic areas 
of professional responsibility, according to standardized protocols.
    In conducting our 12-month finding for YCT we considered all 
scientific and commercial information on the status of YCT that we 
received or acquired between the time of the initial petition (August 
1998) and the time of the final preparation of this finding. However, 
we relied mainly on the published and peer-reviewed documentation for 
our conclusions. Our evaluations of the five factors to the YCT are 
presented below.
    We used the database of May et al. (2003) to examine certain 
aspects of threats and distribution on a watershed by watershed (i.e., 
HUC by HUC) basis. In order to do so, we used the GIS layers provided 
with the database (Hagener 2005). We overlaid the HUC boundaries on the 
conservation population stream layer and recalculated the stream 
lengths that fell within each HUC. Because there are slight 
irregularities in some of the HUC boundaries relative to the stream 
reaches, summarized results are close to, but may not exactly 
replicate, totals given by May et al. (2003). However, the conclusions 
we have drawn remain appropriate.

[[Page 8820]]

Factor A. The Present or Threatened Destruction, Modification, or 
Curtailment of the Species' Habitat or Range

    May et al. (2003) revealed that 59 percent of the habitat for 
extant YCT populations (including both conservation populations and 
sport fish populations) lies on lands administered by Federal agencies, 
particularly the USFS; specifically the Shoshone, Bridger-Teton, 
Caribou-Targhee, Bighorn, Custer, and Gallatin National Forests. 
Moreover, many of the strongholds for YCT conservation populations 
occur within roadless or wilderness areas or national parks, all of 
which afford considerable protection to YCT habitat.
    We are not aware of any comprehensive assessment of habitat status 
or trend that has been conducted across the range of the YCT. An 
extensive body of published literature exists on effects of man-caused 
perturbations to coldwater salmonid habitat (see for example Beschta et 
al. 1987; Chamberlin et al. 1991; Furniss et al. 1991; Meehan 1991; 
Sedell and Everest 1991; Frissell 1993; Henjum et al. 1994; McIntosh et 
al. 1994; Wissmar et al. 1994; U.S. Department of Agriculture and U.S. 
Department of the Interior 1996; Gresswell 1999; Trombulak and Frissell 
2000). This literature provides a record of the types of activities 
that are most detrimental to fish habitat. It further documents the 
physical processes that result from these activities to cause negative 
impacts to coldwater salmonids such as the YCT. Declines in populations 
of native salmonids may result from the combined effects of habitat 
degradation and fragmentation, the blockage of migratory corridors, 
declining water quality or quantity, angler harvest and poaching, 
entrainment (process by which aquatic organisms are pulled through a 
diversion or other device) into diversion channels and dams, introduced 
nonnative species, or other impacts (USFWS 2002). Examples of specific 
land and water management activities that depress salmonid populations 
and degrade habitat include dams and other diversion structures, forest 
management practices, livestock grazing, agriculture, agricultural 
diversions, road construction and maintenance, mining, and urban and 
rural development.
    An important aspect of population demographics, which contributes 
to changes in the range of the YCT as a whole, is the abundance within 
individual populations. Since each population exists under a unique set 
of habitat variables and threats, it is important to consider the trend 
in individual populations as a potential indicator of the status of the 
subspecies as a whole. Unfortunately, few if any populations have been 
adequately monitored to provide quantitative indicators of the 
population trend over the past several generations, due mostly to 
logistical and financial considerations.
    May et al. (2003) conducted a qualitative assessment of the 
viability of each of the 195 conservation populations, based on a 
ranking system where each isolet (a population isolated by physical 
barriers or habitat limitations, typically in a headwater drainage) or 
metapopulation (a set of local populations, among which there may be 
gene flow and extinction and colonization) was ranked from low to high 
for each of 4 population variables. The status assessment (May et al. 
2003) concluded populations at high or moderately high risk occupied 
only 11.2 percent of the range of YCT conservation populations and the 
remaining 88.8 percent were estimated to be at low or moderately low 
    The analysis of risk by watershed, conducted by May et al. (2003), 
is largely congruent with our analysis of occupancy and distribution 
(USFWS 2006). In general, HUCs or watersheds with populations occupied 
by few or scattered isolets are considered at greater risk, due 
primarily to the high degree of isolation. The HUCs with large, 
interconnected metapopulations are generally rated as being at lower 
risk. May et al. (2003) asked the 43 scientists who conducted the 
rankings to determine, for each stream segment, which of 4 categories 
best described their existing knowledge of the demographic status 
(primarily trend) of the population. The YCT conservation population in 
each stream segment was classified as either: (1) Much reduced and 
declining over the long term and/or at a fast rate; (2) reduced and 
declining; (3) reduced from potential, but now fluctuating around 
equilibrium; and, (4) increasing, or fluctuating around equilibrium and 
near potential. Results of this analysis indicated that for the 
Yellowstone River basin only about 17 percent of stream miles 
classified as isolets and 4 percent of miles considered part of 
metapopulations were classified in the two reduced and declining 
categories. For the Snake River basin only about 20 percent of stream 
miles classified as isolets and 24 percent of miles considered part of 
metapopulations were classified in the two reduced and declining 
    While the above analysis is primarily a qualitative indicator of 
population health, it does provide some insight into the overall status 
of the habitat. If habitat was rapidly declining or failing, it stands 
to reason that population status would follow a similar trend. We were 
only partially able to quantitatively assess the threat that 
destruction, modification, or curtailment of habitat may present to YCT 
for this finding. In the YCT review developed by May et al. (2003), the 
biologists who participated were able to identify potential risks to 
habitat in several categories, and they indicated on a stream reach 
basis whether certain land use impacts were present (known) or may be 
present (possible). May et al. (2003) cautioned that the information 
was too qualitative to link land use impacts to specific conservation 
populations and that much of the input was speculative. However, they 
concluded that even with those uncertainties, the information could 
serve to heighten awareness of the possible influences of land uses on 
    The YCT review (May et al. 2003) considered and evaluated land and 
water use impacts to YCT in seven broad categories: (1) Dewatering 
(presumably including other irrigation-related impacts such as 
impediments to fish passage, entrainment, stream channel 
destabilization, etc.); (2) mining (presumably including impacts such 
as effects to water quality, including dispersal of toxic substances 
and sedimentation); (3) range, i.e., livestock grazing (presumably 
including riparian impacts, sedimentation, trampling, and other 
effects); (4) non-angling recreation (primarily identified as impacts 
from four-wheelers, ATVs, nondispersed campsites, recreational 
developments such as ski hills and golf courses, etc.); (5) roads 
(presumably related to a multitude of activities, such as logging, 
transportation corridors, recreational access and including not only 
roads, but also railroads and other utility networks); (6) timber 
harvest (presumably commercial private and public logging activities as 
well as other associated actions of forestry management); and, (7) 
other (including significant impacts not captured in the above, each 
identified in spatially-linked comments in the database to the location 
where they occur).
    In the process of identifying the land use impacts described above, 
and linking them to specific stream segments associated with YCT 
conservation populations, fishery professionals were asked to judge 
whether each activity resulted in ``known,'' ``possible,'' or ``no'' 
impacts (May et al. 2003; see USFWS 2006 for

[[Page 8821]]

more detail). For the 195 designated conservation populations of YCT, 
the most commonly identified land use impact believed to affect the 
status and conservation of YCT was livestock grazing. Grazing was 
identified as a known impact on 45 populations (23 percent of the total 
number of conservation populations) and a possible impact on 97 others 
(50 percent). Thus, May et al. (2003) concluded that livestock grazing 
likely adversely affects nearly \3/4\ of the conservation populations 
of YCT. Grazing was followed, in order of frequency of occurrence 
identified as an impact, by roads (known impact on 33 populations and 
suspected on 66 more); non-angling recreation such as camping, trail 
riding, ATVs, etc. (known impact on 34 populations and suspected on 42 
others); timber harvest (known impact on 31 populations and suspected 
on 35 others); stream dewatering (known impact on 21 populations and 
suspected on 40 others); and mining (known impact on 17 populations and 
suspected on 8 others). This information assessed only the relative 
frequency of these land use factors in affecting YCT populations; it 
did not assess the severity of impacts on a population by population 
basis (May et al. 2003). For example, while impacts from dispersed 
recreation may be pervasive, recreational impacts are not likely to 
severely affect YCT habitat to the extent that more intrusive uses such 
as major water withdrawals or extensive mining activities might in a 
given drainage.
    An evaluation of the land and water use information by stream 
segment (May et al. 2003) reveals watersheds (HUCs) that are likely to 
experience higher magnitude of such impacts, based simply on the known 
presence of such activities (USFWS 2006). Watersheds in the Yellowstone 
River basin where grazing, roads, and timber harvest were considered to 
affect large areas of habitat occupied by conservation populations of 
YCT were in the Upper Yellowstone, Shields, and Upper Wind (May et al. 
2003). Conversely, several HUCs were identified as having large areas 
of conservation habitat with no known impacts. These typically include 
wilderness, national park, or other highly protected areas. Watersheds 
in the Yellowstone River basin that were identified as containing over 
161 km (100 mi) of habitat occupied by conservation populations with no 
known impacts were the Yellowstone Headwaters, Upper Yellowstone and 
Shields. The Upper Yellowstone and Shields HUCs both contain 
substantial habitat that is heavily impacted as well as major portions 
that are relatively unimpacted by land and water management activities.
    In the Snake River basin, areas where grazing, roads, dewatering 
and timber harvest were considered to have known impacts on large areas 
of habitat occupied by conservation populations of YCT were located in 
nearly all HUCs, but were especially pervasive in the Greys-Hobock, 
Palisades, Salt, Teton, and Blackfoot watersheds. The only HUC in the 
Snake River basin identified as having over 161 km (100 mi) of 
conservation habitat with no known impacts was the Snake River 
Headwaters. This information is based on a very coarse analysis and 
should be viewed as preliminary. In a planned 2006 update of the 
database, the information linking habitat impacts to specific 
watersheds is expected to be improved (Brad Shepard, Montana Fish, 
Wildlife and Parks [MFWP], pers. comm. 2005).
    As reported, mining impacts are not pervasive across the range of 
the YCT, but in some instances where they occur they have been noted to 
have particularly severe consequences to aquatic habitat (USFWS 2002). 
The status assessment of May et al. (2003) indicated that known impacts 
of mining on YCT were most widespread in the Yellowstone Headwaters and 
Upper Yellowstone HUCs, as well as in the Gros Ventre, Palisades, Salt 
and Blackfoot watersheds of the Snake River basin, where 24-113 km (15-
70 mi) of YCT conservation populations in each watershed are known to 
have been impacted. Lemly (1999) described a particularly threatening 
scenario in the Blackfoot River drainage of Idaho where very high 
selenium concentrations were first discovered. A preliminary hazard 
assessment indicated that waterborne selenium concentrations in the 
Blackfoot River and 14 of its tributaries met or exceeded toxic 
thresholds for fish. The selenium problem centers on surface disposal 
of mine spoils. Compounding this problem is the presence of historic 
tailings dumps, many of which are large (>10 million cubic meters [353 
million cubic feet]) and contain a tremendous reservoir of selenium 
that has the potential to be mobilized and introduced into aquatic 
habitats (Lemly 1999). Continued expansion of phosphate mining is 
anticipated in these watersheds, and large mineral leases are awaiting 
development both on and off National Forest lands (Lemly 1999, 
Christensen 2005). This may be a serious and evolving situation. 
However, while selenium poisoning should not be minimized as a threat 
to conservation populations of YCT in the Blackfoot and Salt River 
watersheds, it remains a localized threat and would not be expected to 
cause rangewide losses of YCT conservation populations.
    Another localized threat occurs in the Teton River watershed, where 
Koenig (2005) and Benjamin (2005) reported that YCT populations have 
experienced precipitous declines in recent years. These declines are 
hypothesized to be linked to poor recruitment. Koenig (2005) 
investigated whether specific habitat attributes could be limiting 
cutthroat fry recruitment and at which life stage a recruitment 
bottleneck may be operating. His conclusions were that the number of 
cutthroat fry is more likely limited by low seeding than by spawning 
habitat availability. Koenig (2005) further concluded that low survival 
of age-1 cutthroat trout may be attributable to competition with 
introduced rainbow and brook trout for overwinter habitat. Benjamin 
(2005) speculated that water shortages and stream dewatering have 
played a major role in the decline of YCT in the Teton River basin.
    In Idaho, the State manages approximately 292,000 hectares (722,000 
acres) of Endowment lands. These lands include approximately 200 km 
(124 mi) of perennial streams that Idaho Department of Fish and Game 
(IDFG) has identified as providing habitat for the YCT (Caswell and 
Huffaker 2005). The predominant use of these lands is livestock 
grazing, though some timber harvest also occurs. Where timber harvest 
occurs on those lands, the State of Idaho reports that the Department 
strictly adheres to the rules and guidelines provided by Idaho's Forest 
Practices Act (Caswell and Huffaker 2005).
    There are substantial portions of the range where habitat threats 
appear to be limited. Wichers (2005) reported that the upper 
Yellowstone River above Yellowstone Lake appears not to be subject to 
genetic or habitat threats, due largely to the remote wilderness 
setting (see USFWS 2006 for additional discussion).
    In Yellowstone National Park (YNP), of the approximately 3,132 km 
(1,946 mi) of stream originally supporting resident or fluvial YCT 
(mostly outside of the Yellowstone Lake and River drainage above the 
Lower and Upper Falls), 65 percent (2,025 km [1,258 mi]) continue to 
support nonintrogressed fish, and 35 percent (1,107 km [688 mi]) now 
are home to fish hybridized to varying degrees with nonnative rainbow 
trout (Lewis 2005).
    In Utah and Nevada, the range of YCT is restricted to a few 
headwater streams

[[Page 8822]]

in the lower Snake River portion of the range, specifically in the 
Goose and Raft HUCs. Utah and Nevada are part of the Interstate 
Yellowstone Cutthroat Trout Working Group. They participated in the YCT 
status assessment (May et al. 2003), but they have not provided 
specific comments for this status review (USFWS 2006) regarding updates 
to status or distribution. The States of Idaho, Montana, and Wyoming 
comprise approximately 98 percent of the range of YCT conservation 
    The Center for Biological Diversity (Greenwald 2005) submitted an 
alternative analysis of the data presented in May et al. (2003). 
According to Greenwald (2005), these results clearly indicate that 
ongoing habitat degradation is threatening remaining YCT populations. 
We refer the reader to our previous discussion of the limitations of 
the data on known habitat impacts presented in May et al. (2003). In 
contrast with the Center for Biological Diversity (Greenwald 2005), the 
USFWS finds that the mere presence of an activity within a stream 
segment that hosts a conservation population is not sufficient evidence 
to conclude that the population is threatened. Additional parameters, 
such as distribution and abundance, as well as recent trends must be 
factored into an overall status determination. Otherwise, logic would 
dictate that every species that comes in contact with managed 
landscapes is threatened by those human influences. Such a conclusion 
is not reasonable.
Summary of Factor A
    In summary, populations of YCT that meet the State management 
agency standards as conservation populations (i.e., those populations 
we are considering YCT for purposes of this finding), are well-
distributed and relatively secure in at least nine HUCs (i.e., 
watersheds) in the central headwaters of their native range. In the 
Yellowstone River basin, we find that populations in the HUCs of the 
Yellowstone Headwaters (1,308 km [813 mi] of occupied habitat), Upper 
Yellowstone (822 km [511 mi]), and Shields (653 km [406 mi]) form the 
central core of the YCT range and these populations are well-
distributed (collectively providing 64 percent of the habitat occupied 
by conservation populations in the Yellowstone River drainage). In the 
Snake River basin, the central core of the range for the YCT 
conservation populations also is located in the headwaters, along the 
Continental Divide. The six strongest remaining conservation 
populations of YCT in the Snake River basin are in Greys-Hobock (1,051 
km [653 mi] of occupied habitat), Snake Headwaters (716 km [445 mi]), 
Salt (694 km [431 mi]), Teton (644 km [400 mi]), Palisades (501 km [311 
mi]), and Gros Ventre (414 km [257 mi]) watersheds. Conservation 
populations in these HUCS are generally well-distributed (collectively 
providing 68 percent of the habitat occupied by conservation 
populations in the Snake River drainage).
    As a result of the present information, and as discussed more 
thoroughly in the status review (USFWS 2006), we conclude the best 
scientific and commercial information available to us indicates that 
present or threatened destruction, modification, or curtailment of 
habitat or range has not affected the status of YCT to the extent that 
listing under the ESA as a threatened or endangered species is 
warranted at this time. Although YCT distribution has declined, perhaps 
by more than 50 percent over the past 200 years (May et al. 2003), our 
analysis indicates that YCT strongholds remain in at least three major 
watersheds of the upper Yellowstone River basin and six major 
watersheds of the upper Snake River basin. These nine HUCs collectively 
form a solid basis for persistence of conservation populations of YCT.

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

    In the YCT status assessment (May et al. 2003) consideration was 
given to the effects of angling on population status. Angling was 
considered to have a known impact on 54 of 195 conservation populations 
(28 percent) and a possible impact on 22 other populations. In total, 
then, recreational angling was considered by May et al. (2003) to 
impact up to about 40 percent of the 195 designated conservation 
populations of YCT.
    Our status review (USFWS 2006) revealed that each of the States and 
the National Park Service have greatly restricted the angler harvest of 
YCT. May et al. (2003) noted that restrictive angling regulations have 
been implemented for YCT on waters comprising nearly half of the 195 
designated conservation populations of YCT. In many regions, catch-and-
release is the only type of angling that is allowed (Caswell and 
Huffaker 2005; Hagener 2005; Koel et al. 2005; Osborne 2005; Wyoming 
Game and Fish Department [WGFD] 2005). However, catch-and-release 
angling regulations are not essential to protecting YCT from excessive 
harvest by anglers in all waters.
    Although overfishing contributed to the decline of YCT in specific 
locations in the past, overfishing or overcollection is not currently 
perceived as a threat to YCT in Montana (Hagener 2005), Idaho (Caswell 
and Huffaker 2005), or Wyoming (WGFD 2005). These activities are 
tightly regulated and have become increasingly restrictive. Enforcement 
of regulations pertaining to native fish is a priority. Extensive 
education and signing efforts have been undertaken to help anglers 
identify YCT and to encourage their support for YCT conservation 
efforts (e.g., Hagener 2005). Collection of YCT for scientific and 
educational purposes is regulated by State agencies and is allowed only 
for valid, scientific purposes. Collection methods, locations, and 
timing are stipulated as part of the conditions of the permits.
    In YNP, in order to ensure that the native YCT populations within 
the Park continue to persist into the foreseeable future even with a 
high degree of angling pressure, the Park instituted a mandatory catch-
and-release regulation for cutthroat trout and other native park fish 
species in 2001 (Lewis 2005). Recently, they have proposed liberalizing 
harvest limits for nonnative species that exist in waters that also are 
inhabited by native cutthroat trout (Lewis 2005).
    Threats from legal recreational angling are easier to control 
through regulatory actions than are threats from most land and water 
management activities. Where legal angling is considered a risk, 
restrictive regulations continue to be implemented, sometimes with 
dramatic results. For instance, directed harvest on rainbow trout was 
rapidly initiated in the South Fork Snake River, upon discovery that 
the rainbow trout population was expanding and threatening the YCT 
population (J. Fredericks in litt., IDFG, 2005).
Summary of Factor B
    Although overfishing contributed to the decline of YCT in specific 
locations in the past, overfishing or overcollection is not currently 
perceived as a threat to YCT. Therefore, we conclude the best 
scientific and commercial information available to us indicates that 
overutilization for commercial, recreational, scientific, or 
educational purposes has not affected the status of YCT to the extent 
that listing under the ESA as a threatened or endangered species is 

[[Page 8823]]

Factor C. Disease or Predation

    The risk of transmitting disease while relocating wild or hatchery 
fish into new waters is addressed via policies and State statutes 
(Caswell and Huffaker 2005; Hagener 2005; WGFD 2005). For example, in 
Montana, policy requires that an environmental assessment be completed 
for all introductions of a species into waters where the species is not 
found. The environmental assessment process provides for evaluation of 
impacts to resident native species and public review. Before fish are 
relocated, fish from the donor source are inspected for the presence of 
any pathogen that might preclude the transfer. Approval of all fish 
transfers requires the approval of the Fisheries Division Administrator 
after consultation with the Fish Health Committee. Reducing the risk of 
amplifying or spreading disease by hatchery operations is considered 
important (Hagener 2005).
    All fish hatcheries (Federal, State, and private) typically undergo 
annual fish health inspections as authorized by State statute. In 
Montana, for example, all hatcheries are required to report the 
presence of fish pathogens, and damages resulting from spread of 
diseases can be collected from the violator. The Montana Fish Wildlife 
and Parks (MFWP) has spent several million dollars during the past 10 
years to upgrade and protect State hatchery water sources so that 
whirling disease and other pathogenic organisms cannot get into 
hatchery water supplies (Hagener 2005). Before any fish lot is stocked 
from a State facility, it is inspected for the presence of disease. 
Diseased fish cannot be stocked from State hatcheries. Because of the 
possible introduction of fish pathogens, MFWP does not bring wild fish 
into any of its salmonid hatcheries. Additionally, movement of fish 
between salmonid hatcheries is prohibited except in extreme emergencies 
and must be approved by the Fisheries Division Administrator and the 
Fish Health Committee (Hagener 2005).
    As part of this 12-month finding, we consider the threat that 
diseases may pose to YCT. Except for whirling disease, the fish 
pathogens that occur in the natural habitats of YCT are mainly benign 
in wild populations and typically cause death only when the fish are 
stressed by severe environmental conditions. Whirling disease is caused 
by the exotic myxozoan parasite Myxobolus cerebralis. That microscopic 
parasite was introduced to the eastern United States from Europe in the 
1950s, and has since been found in many western States. Two separate 
host organisms are necessary for completion of the parasite's life 
cycle, a salmonid (i.e., salmon, trout, and their close relatives) fish 
and a specific aquatic oligochaete worm (Tubifex tubifex).
    Whirling disease has been identified in fish populations in 148 
watersheds in Montana, including sites on upper Yellowstone River, in 
the Shields River, and in the Clarks Fork of the Yellowstone where YCT 
occur (Hagener 2005). To date, whirling disease has not been detected 
in any wild YCT populations in Montana and has not been documented as 
causing any impacts to Montana YCT populations. In Montana, actions 
continue to be taken to prevent the spread of whirling disease and to 
minimize the impact of this disease on native fish (Hagener 2005).
    Whirling disease has been reported in wild YCT from Henrys Lake, 
Teton River, South Fork Snake River, and Blackfoot River in Idaho 
(Caswell and Huffaker 2005). It also has been documented in rainbow 
trout populations in several of the watersheds occupied by YCT in close 
    In Wyoming, the whirling disease parasite was first detected in 
1996 on the South Fork Shoshone River with the infection suspected to 
have originated from privately stocked fish ponds adjacent to the river 
(WGFD 2005). Since that time, the organism has spread elsewhere 
throughout portions of Wyoming (USFWS 2006). To date, WGFD has not 
observed a population impact on YCT from whirling disease in State-
managed waters.
    Whirling disease has been implicated in the decline of YCT in 
Yellowstone Lake (Koel et al. 2005). The parasite Myxobolus cerebralis 
was discovered in Yellowstone Lake in 1998, among juvenile and adult 
cutthroat trout (Koel et al. in press 2006). Examination of specimens 
obtained as gillnetting mortalities has since confirmed the presence of 
the parasite throughout Yellowstone Lake, with highest prevalence 
existing in the northern region of the lake, near known infected 
streams. Although widespread presence of this harmful parasite in the 
lake has been documented, it is encouraging that the prevalence of 
parasitic spores in adult fish suggests some cutthroat trout are 
surviving initial infection (Koel et al. 2005).
    The impacts of whirling disease in YNP have been most severe in 
Pelican Creek (Koel et al. 2005), where few wild-reared fry have been 
observed in recent years (2001-2004). Cutthroat trout sentinel fry 
exposures (i.e., experiments with caged fish) in this tributary have 
indicated that over 90 percent of the fry were infected with the 
parasite, with an average severity (by histological examination) of 
greater than ``4'' on a scale of ``0'' (no infection) to ``5'' (most 
severe infection; Koel et al. 2004). The spawning cutthroat trout 
population of Pelican Creek, which in 1981 totaled nearly 30,000 fish 
(Jones et al. 1982), has been essentially lost (Koel et al. 2005). 
Angling in the Pelican Creek drainage was completely closed in 2004, in 
an attempt to slow the dispersal of the whirling disease parasite to 
other Park waters.
    Although the whirling disease parasite continues to spread in many 
waters of the western United States (Bartholomew and Reno 2002) and is 
now widespread in portions of the habitat occupied by YCT, few 
outbreaks of whirling disease in resident fishes have occurred (Caswell 
and Huffaker 2005; Hagener 2005; WGFD 2005). Studies summarized by 
Downing et al. (2002) indicated that presence of the whirling disease 
parasite does not portend outbreaks of the disease in resident fishes. 
For example, although 46 of 230 sites tested in Montana were positive 
for the parasite, disease outbreaks were known to have occurred at only 
6 of those sites. Downing et al. (2002) provided evidence that the 
frequent absence of manifest symptoms of whirling disease in resident 
trout, despite presence of the parasite, is due to complex interactions 
among the timing and spatial locations of important host-fish life-
history events (e.g., spawning, fry emergence from stream gravels, and 
early-life growth) and spatial and temporal variation in the occurrence 
of the parasite itself. Only under specific conditions, which evidently 
occur only in a small proportion of the locations where the parasite 
has been found, are those interactions such that disease outbreaks 
occur in resident fishes.
    Studies conducted on various salmonids by Vincent (2002) confirmed 
that YCT were moderately susceptible to whirling disease. All of the 
cutthroat trout he tested (including YCT of both the large-spotted and 
fine-spotted forms as well as westslope cutthroat trout [WCT]) were 
found under captive experiments to show significantly lower average 
infection intensity than all of six different rainbow trout strains. 
The WCT were found in those tests to have significantly lower infection 
rates than either of the YCT. We are unaware of any studies of the 
susceptibility of the hybrids of rainbow trout and YCT to whirling 

[[Page 8824]]

    The YCT status assessment report (May et al. 2003) concluded that 
the threats to extant YCT populations from diseases in general were 
greater for the extensive YCT metapopulations than for the smaller YCT 
populations that occur as isolets. The key assumption made in reaching 
that conclusion was that because the ranges of individual 
metapopulations were naturally much larger and encompassed habitats 
more diverse than those of isolets, the probability that diseases may 
be introduced and become established in YCT populations and spread 
through migratory behavior was greater for metapopulations than isolets 
(May et al. 2003).
    Extensive research is continuing to determine the distribution of 
whirling disease, the susceptibility of YCT and other fishes to 
whirling disease, infection rates, and possible control measures 
(Bartholomew and Wilson 2002). Although no means have been found to 
eliminate the whirling disease parasite from streams and lakes, the 
States have established statutes, policies, and protocols that help to 
prevent the human-caused spread of extant pathogens and the 
introduction of new pathogens. The available scientific information 
specific to whirling disease thus indicates considerable variation in 
the probable disease threat among individual YCT populations and 
provides evidence that the disease is not a significant threat to the 
majority of populations constituting YCT (see USFWS 2006 for more 
    The instances when predation by other fishes may negatively affect 
extant YCT populations are thought to be fairly well distributed across 
the range, but are not well documented. Some authors have identified 
nonnative species as one of the greatest threats to cutthroat trout of 
the intermountain West (see for example--Gresswell 1995; Kruse et al. 
2000; Dunham et al. 2004). Predation, or other forms of interaction 
with nonnative fish, threatens native YCT in both managed landscapes 
and in some relatively secure unaltered habitats, including roadless 
areas, wilderness areas, and national parks. Based on observations to 
date, YCT that have the adfluvial or fluvial life history may be most 
susceptible to the effects of predation by nonnative fishes.
    Introduced brown trout are well established in much of the range of 
YCT, occurring primarily in rivers and their larger tributaries, where 
they likely compete for food and space and prey on cutthroat trout. 
Elevated water temperatures may often favor brown trout, which are 
adaptable to such conditions over native species like YCT. 
Introductions of nonnative game fish such as brown trout also can be 
detrimental due to the increased angling pressure they may attract, 
which can result in the subsequent incidental catch and harvest of YCT.
    The illegal introduction and subsequent establishment of a 
reproducing lake trout population in Yellowstone Lake has had far-
reaching consequences and serves as a well-documented example of such 
impacts in the range of YCT. With the recent invasions by lake trout 
(and whirling disease), YNP is placing a high priority on preservation 
and recovery of YCT, particularly in Yellowstone Lake. Introduced lake 
trout have already resulted in the decline of cutthroat trout (Koel et 
al. 2005) and the problem also may have consequences to the food web, 
including impacts on grizzly bears and other consumers (Koel et al. 
2005; Lewis 2005). Nonnative lake trout are not viewed as a suitable 
ecological substitute for cutthroat trout in the Yellowstone Lake 
system because they are inaccessible to most consumer species (Koel et 
al. 2005). Lake trout tend to occupy greater depths within the lake 
than do cutthroat trout. Lake trout remain within Yellowstone Lake at 
all life stages and they do not typically enter tributary streams, as 
do cutthroat trout.
    Bioenergetics modeling suggests that an average-sized mature lake 
trout in Yellowstone Lake will consume 41 cutthroat trout per year 
(Ruzycki et al. 2003). Following the guidance of a lake trout expert 
advisory panel (McIntyre 1995), the National Park Service initiated 
gillnetting to determine the spatial and temporal distribution of lake 
trout within Yellowstone Lake (Koel et al. 2005). The efforts have led 
to a long-term lake trout removal program for the protection of the 
cutthroat trout in this system (Mahony and Ruzycki 1997; Bigelow et al. 
    Lake trout densities in the West Thumb of Yellowstone Lake remain 
high and pose an ongoing threat to the cutthroat trout (Koel et al. 
2005). The goals of controlling lake trout and rehabilitating 
historical cutthroat trout abundance in Yellowstone Lake are yet to be 
achieved. Relatively low lake trout catch per unit effort and an annual 
decrease in the size of sexually mature lake trout are indicators that 
the removal program is exerting pressure on the lake trout population 
(Koel et al. 2005).
    The lake trout threat in Yellowstone Lake is relatively new, occurs 
in a unique ecological setting, and involves a predaceous nonnative 
fish species (lake trout) that has a limited history of sympatry with 
YCT (due partly to the relative scarcity of natural adfluvial 
populations of YCT). A similar set of circumstances occurs in nearly a 
dozen large headwater lakes of the Columbia River basin, located mostly 
in and around Glacier National Park. Introduced populations of lake 
trout have become established there and have dramatically expanded in 
sympatry with native bull trout (Salvelinus confluentus) and WCT in 
recent years. The initial lake trout introduction in Flathead Lake 
occurred about 100 years ago and to date cutthroat trout have not been 
extirpated from the lakes in the Flathead River system, but major food 
web perturbations have occurred (Spencer et al. 1991). Some populations 
of native fish persist only at very low levels (Fredenberg 2002). We 
believe there is a level of uncertainty over the eventual outcome of 
the competitive interaction between lake trout and YCT in Yellowstone 
Lake. The USFWS finds reason for concern over the future of the 
Yellowstone Lake population of YCT, and we will monitor this situation 
closely. However, given the large scope of the Yellowstone Lake 
ecosystem and ongoing conservation actions, we believe that 
conservation populations of YCT will persist in this ecosystem, at 
least for the foreseeable future.
    We concur with Greenwald (2005), who submitted comments that 
asserted: ``Where YCT are able to persist in sympatry with nonnative 
trout, their overall numbers and biomass may be greatly reduced. This 
is very likely a major factor, along with habitat degradation, in the 
restriction of the YCT to isolated, high-elevation, headwater 
streams.'' Greenwald (2005) noted that May et al. (2003) did not 
compile data on the presence of non-hybridizing trout in YCT streams 
(e.g., brown trout, brook trout), but concluded it is safe to say that 
many of their conservation populations and the nonintrogressed 
populations are in fact sympatric with nonnative trout. Greenwald 
(2005) advocated that YCT populations existing in sympatry with 
predaceous nonnative fish were not secure and are in fact, threatened 
with extirpation. Nonnative trout that do not hybridize with cutthroat 
have undoubtedly caused historical reductions in the size and 
distribution of conservation populations of YCT across substantial 
portions of the range. However, most of these introduced trout 
populations have been in place for many decades, if not a century or 
more, and they have not caused widespread

[[Page 8825]]

extirpation of YCT. Nonetheless, active programs to suppress or remove 
nonnative trout from waters where YCT populations exist are encouraged 
and in some areas are being initiated (USFWS 2006).
Summary of Factor C
    As a result of this analysis, we conclude the best scientific and 
commercial information available to us indicates that neither whirling 
disease nor other nonnative disease organisms have affected the status 
of YCT to the extent that listing under the ESA as a threatened or 
endangered species is warranted at this time. Additionally, we conclude 
the best scientific and commercial information available to us 
indicates that predation from brown trout, lake trout, or other 
predaceous, nonnative fishes has not affected the status of YCT to the 
extent that listing under the ESA as a threatened or endangered species 
is warranted. However, where such predation does occur, often on YCT 
that have either the fluvial or adfluvial life history, it can have 
serious consequences to conservation populations. The impacts of some 
remaining, nonnative fishes overlapping with YCT (e.g., brook trout) 
will be discussed in subsequent sections (see Factor E) of this 
    We believe that intensive monitoring and evaluation of the status 
of conservation populations of YCT and their overlapping competitors 
over time is necessary and may ultimately indicate whether nonnative 
species control actions have been adequately implemented and effective. 
If the current trend of nonnative species expansion cannot be halted, 
some conservation populations of YCT will likely exhibit a downward 
trend over time, and at some point the species may become threatened, 
largely as a result of those nonnative species interactions. However, 
at this time the best scientific and commercial evidence available to 
us does not suggest that the YCT is impacted across its range to the 
extent that listing under the ESA as a threatened or endangered species 
is warranted.

Factor D. Inadequacy of Existing Regulatory Mechanisms

    The ESA requires us to examine the adequacy of existing regulatory 
mechanisms with respect to those extant threats that place the species 
in danger of becoming either threatened or endangered. In the United 
States, YCT are generally managed as a sought-after game fish species 
by State fish and wildlife managers in most of the watersheds where 
they occur. Each management jurisdiction bases its fishing regulations 
on local fish population information, consistent with its overall 
regulatory framework and public review process, as well as broader 
general management plans and objectives (Caswell and Huffaker 2005; 
Hagener 2005; Lewis 2005; Wichers 2005). However, the management 
authorities that develop and set the angling regulations typically do 
not own or manage the habitat in the watersheds inhabited by 
conservation populations of the YCT. Most of that habitat is managed by 
Federal land management agencies. Notable major exceptions occur in YNP 
and on all or portions of Native American Indian Reservations, where 
ownership and management are consolidated. Coordination in 
implementation of regulatory mechanisms that are designed to protect 
the habitat, with angling regulations allowing public enjoyment of the 
species, is vitally important. Numerous examples were submitted to the 
USFWS where such coordinated efforts were highlighted (Caswell and 
Huffaker 2005; Hagener 2005; Lewis 2005; McAllister 2005; Wichers 
Regulatory Mechanisms Involving Land Management
    The status assessment report (May et al. 2003) revealed that 
approximately 59 percent (7,125 of the 12,115 km [4,427 of the 7,528 
mi]) of habitat presently occupied by all YCT populations (including 
both conservation and sport fish populations) lies on lands managed by 
Federal agencies. Included within that total are lands with special 
management, including those designated as national parks (10 percent of 
all occupied habitat on Federal lands), USFS-administered wilderness 
areas (14 percent), or other USFS-administered roadless areas (19 
percent). Additional lands managed as roadless by the Bureau of Land 
Management (BLM) were not quantified, but would add to this total. In 
summary, about half of the federally managed land occupied by YCT 
occurs in some form of protected habitat.
    Numerous State and Federal laws and regulations exist that help to 
prevent adverse effects of land management activities on YCT. Federal 
laws that protect YCT and their habitats include the Clean Water Act, 
Federal Land Management Protection Act, National Forest Management Act, 
Wild and Scenic Rivers legislation, Wilderness Act, and the National 
Environmental Policy Act (NEPA). The USFS and BLM have adopted the 
Inland Native Fish Strategy or similar standards in waters of the Snake 
River Basin west of the Continental Divide, that includes standards and 
guidelines that help protect the biological integrity of watersheds. 
The USFS classifies YCT as a ``sensitive'' species. As a result, 
Biological Evaluations include appropriate mitigation for any Forest 
project that has the potential to affect YCT.
    Greenwald (2005), in comments submitted for the status review 
(USFWS 2006), asserts that the National Forest Management Act and other 
laws are inadequate and their implementation is insufficient to provide 
necessary protections to YCT on USFS lands. However, we have based our 
analysis of listing Factor D (Inadequacy of Existing Regulatory 
Mechanisms) primarily on the best available scientific and commercial 
information regarding the status and trend of the species. We found the 
record did not indicate that status and trend of YCT is declining in a 
broad pattern, or to such an extent that would indicate a failure of 
existing laws and regulatory mechanisms to provide for sufficient 
protection of the species habitat on National Forest lands. Greenwald 
(2005) cites numerous examples of purportedly inadequate environmental 
assessments for timber sales, inadequate resource management plans, 
etc., but evidence of ostensibly resultant impacts to the YCT 
populations was not provided.
    Few other aquatic species listed under the ESA overlap the 
distribution of YCT, so YCT currently receive minimal protection from 
the ESA's section 7 consultation provisions. Salmon, steelhead, and 
bull trout in the Snake River system are all found downstream of 
Shoshone Falls (River Mile 614.7), outside the recent historical range 
of YCT. Two ESA-listed snail species, the endangered Utah valvata 
(Valvata utahensis) documented to occur in the lower Henry's Fork and 
in the mainstem Snake River from the mouth of the Henry's Fork 
downstream to Grandview (River Mile 487), and the endangered Snake 
River physa (Haitia natricina) known to occur in the mainstem Snake 
River from Grandview (River Mile 487) as far upstream as Minidoka Dam 
(River Mile 674.5), are within the range of YCT. The threatened wetland 
plant, Spiranthes diluvialis (Ute ladies'-tresses), occurs in wetlands 
along the mainstem Snake River downstream from the Palisades Dam to 
American Falls Reservoir and along the Henry's Fork.
    Temperature regime also is identified as one of the most important 
water quality attributes affecting distribution of some native 
salmonids (Rieman and McIntyre 1995; Adams and Bjornn 1997). The U.S. 

[[Page 8826]]

Protection Agency (EPA) works with USFWS, State environmental quality 
agencies, and other entities to develop regional temperature guidance 
(USFWS 2002). The goals are to develop EPA regional temperature 
criteria guidance that--(1) meet the biological requirements of native 
salmonid species for survival and recovery pursuant to the ESA, provide 
for the restoration and maintenance of surface water temperature to 
support and protect native salmonids pursuant to the Clean Water Act, 
and meet the Federal trust responsibilities with treaty tribes for 
rebuilding salmon stocks, (2) recognize the natural temperature 
potential and limitations of water bodies, and (3) can be effectively 
incorporated by States and Tribes in programs concerned with water 
quality standards. States and Tribes will use the new criteria guidance 
to revise their temperature standards, and if necessary, the EPA and 
other agencies will use the new criteria guidance to evaluate State and 
Tribal standard revisions.
    In Idaho, State regulatory mechanisms that provide some protection 
for YCT habitat include the Stream Channel Protection Act, the Lake 
Protection Act, and the Forest Practices Act (Caswell and Huffaker 
2005). Wyoming has similar regulatory oversight (WDFG 2005). Montana 
laws that benefit YCT include the Montana Stream Protection Act, the 
Streamside Management Zone Law, the Montana Natural Streambed and Land 
Preservation Act, and the Montana Pollutant Discharge Elimination 
System (Hagener 2005). The Montana Stream Protection Act requires a 
permit be obtained for any project that may affect the natural and 
existing shape and form of any stream or its banks or tributaries.
    Other State laws, rules, and regulatory mechanisms that help ensure 
the conservation of YCT and their habitat in Utah and Nevada are not 
discussed, but they are similar to those in the three States (Idaho, 
Montana, and Wyoming) where 98 percent of the extant range of the YCT 
Regulatory Mechanisms That Address Threats From Hybridizing, Nonnative 
    Stocking has been part of Idaho's fisheries management for many 
years; indeed, fish stocking is recognized as an integral part of 
Idaho's fisheries policy (IDFG 2005). In Idaho, regulatory mechanisms 
that will minimize the potential for additional threats to extant YCT 
populations from hybridization are now in place (Caswell and Huffaker 
2005). The IDFG management efforts to reduce hybridization have 
expanded greatly in the past few years. Since 1999, it has been the 
policy of IDFG to stock YCT waters with only rainbow trout from eggs 
that were heat-shocked to produce triploidy and sterility (Caswell and 
Huffaker 2005), thus reducing fish stocking as a source of hybridizing 
rainbow trout. The IDFG management direction, as described in its 
Fisheries Management Plan (a publicly reviewed, Commission-adopted 
document), gives priority in management decisions to wild, native 
populations of fish. In addition, the transport of live fish to, 
within, and from Idaho is regulated by the IDFG and the Idaho 
Department of Agriculture. The IDFG regulates private ponds in the 
State and applies the same criteria to private-pond stocking that it 
does to the stocking of public waters (i.e., stocking of potentially 
hybridizing fishes that may pose a hybridization threat to native 
cutthroat trout is prohibited).
    Partially in recognition of past problems caused by indiscriminant 
fish stocking, Montana has adopted a number of laws and regulatory 
mechanisms that address threats posed by the unlawful stocking of 
potentially hybridizing, nonnative fishes (Hagener 2005). These include 
State statutes, rules, and policies that restrict the capture, 
possession, transportation, and stocking of live fish, including fishes 
that may hybridize with YCT, as well as rigorous fish-health policies 
that restrict the transport or stocking of live fish. The stocking of 
private ponds also is closely regulated (Hagener 2005). Furthermore, 
although the stocking of rivers and streams with a variety of nonnative 
fishes was routine early in the 20th Century, it no longer occurs in 
Montana. In 1976, Montana adopted a policy that prohibits the stocking 
of hatchery fish in rivers and streams. Consequently, unless done for 
government-sponsored conservation purposes, no other trout or nonnative 
fish may be stocked in rivers and streams inhabited by YCT in Montana.
Regulatory Mechanisms That Address Threats From Pathogens
    The MFWP has established a Fish Health Committee to review all 
projects and policies that involve fish health issues and is in the 
process of finalizing its Fish Health Policy. This policy establishes 
monitoring protocols for State, Federal, and private fish hatcheries; 
identifies four classifications of fish pathogens; outlines the 
policies and, where appropriate, the permitting processes for 
importation or transfer of fish, fish eggs and fish parts; establishes 
disinfection procedures of hatchery equipment, hatchery facilities, and 
fish eggs; delineates the hatchery quarantine process and procedures; 
and establishes policies regarding the importation of aquatic animals.
    Montana limits the threat of importation of fish pathogens by 
restricting the importation of fish, leeches, and crayfish (Hagener 
2005). Importations of fish and fish gametes require an import permit. 
Sources of imported fish, fish gametes, and leeches must pass a 
rigorous fish health certification process. Nonnative aquatic nuisance 
species (ANS) include nonindigenous animal and plant species and 
pathogens that can potentially impact native species or their 
environments. The ANS may pose a threat to YCT and other Montana native 
species through competition, predation, or disruption of the ecology of 
their environment (Hagener 2005). In order to proactively respond to 
this threat, MFWP formed the Montana Aquatic Nuisance Species Technical 
Committee that has completed an Aquatic Nuisance Species Management 
Plan that addresses the illegal importation of exotic aquatic animals, 
plants, and pathogens. Led by the MFWP ANS Program Coordinator, Montana 
coordinates State efforts and funding to prevent accidental 
introductions of ANS, limit the spread of established ANS, and 
eradicate ANS where feasible.
    In Wyoming, similar State regulatory practices are in place. In 
Utah and Nevada, the range of YCT is restricted to a few headwater 
streams in the lower Snake River portion of the range, specifically in 
the Goose and Raft HUCs. For the most part, applicable State laws and 
regulations in Utah and Nevada are similar to those detailed in the 
other three States (Idaho, Montana, and Wyoming) which comprise 
approximately 98 percent of the YCT range.
    Greenwald (2005) submitted comments for this status review (USFWS 
2006) indicating that the Interstate Yellowstone Cutthroat Trout 
Working Group Memorandum of Agreement and a similar Conservation 
Agreement for YCT within Montana are voluntary agreements that do not 
qualify as regulatory mechanisms. The USFWS agrees with that assessment 
and based its finding of the listing status of YCT on the best 
available scientific and commercial information regarding the status 
and threats to YCT, not on the promised or anticipated results of 
conservation actions.
Summary of Factor D
    Our status review (USFWS 2006) has not revealed information to 
indicate that regulatory mechanisms related to land

[[Page 8827]]

management or fisheries management are not working, or will not work to 
protect YCT in the future. As a result of this status review (USFWS 
2006) we conclude that the best scientific and commercial information 
available to us indicates that any identified inadequacies of existing 
regulatory mechanisms have not affected the status of YCT to the extent 
that listing under the ESA as a threatened or endangered species is 

Factor E. Other Natural or Manmade Factors Affecting the Species' 
Continued Existence

Fragmentation and Isolation of Small YCT Populations in Headwater Areas
    Extant YCT populations are not necessarily small or limited to 
headwater streams. Instead, May et al. (2003) indicated that many river 
drainages had numerous, interconnected miles of stream habitat occupied 
by YCT. Those areas include the nine watersheds previously described as 
forming the central core of YCT conservation efforts (Yellowstone 
Headwaters, Upper Yellowstone, and Shields in the Yellowstone River 
Basin [see Table 1 and Figure 2 in USFWS 2006]; Snake Headwaters, Gros 
Ventre, Greys-Hobock, Palisades, Salt, and Teton in the Snake River 
basin [see Table 2 and figure 2 in USFWS 2006]).
    Although YCT remain widely distributed in two headwater basins, the 
effects of human activities combined with natural factors have reduced 
the overall distribution and abundance of YCT to an undetermined extent 
over the past two centuries (May et al. 2003). Multiple local 
populations distributed throughout a watershed provide a mechanism for 
spreading risk because the simultaneous loss of all local populations 
is unlikely. Migratory corridors allow individuals access to unoccupied 
but suitable habitats, foraging areas, and refuges from disturbances. 
Where migratory life history forms of salmonid species are not present, 
isolated populations cannot be replenished naturally when a disturbance 
makes local habitats unsuitable.
    Our status review (USFWS 2006) found little direct evidence that 
the geographic isolation of YCT populations had resulted in stochastic 
extirpations of such populations (due, for example, to natural events 
such as floods, landslides, or wildfires). Given the lack of such 
evidence it logically follows that such threats are unlikely to occur 
to such a degree as to threaten the YCT subspecies or substantial 
portions thereof (USFWS 2001). However, the historical record indicates 
the distribution of YCT has been substantially reduced over the past 
200 years and it is likely that catastrophic natural events contributed 
at some level to that loss, even if only affecting isolated 
populations. Conservation populations of YCT were determined by May et 
al. (2003) to be currently absent from five watersheds where they 
historically existed (Pompeys Pillar, Lake Basin, Popo Agie, Lower Wind 
River, Lake Walcott), and distribution was extremely limited in single 
isolet populations extending through less than 16 km (10 mi) of stream 
in five other HUCs (Pryor, Little Bighorn, Upper Tongue, Shoshone, and 
North Fork Shoshone). For the most part, these watersheds are in the 
downstream margins of the range of YCT, where populations are 
noticeably fragmented, and may have been so, historically. We were not 
able to determine how much of the currently restricted range of those 
populations is due primarily to habitat suitability vs. other threats 
such as hybridization with rainbow trout.
    Information provided in the YCT status assessment (May et al. 2003) 
ranked each of four measures of population viability that could make 
YCT vulnerable to catastrophic natural events or adverse human effects 
on the aquatic environment--(1) population productivity (i.e., 
demographics), (2) temporal variability, (3) isolation, and (4) 
population size. That analysis suggested isolets were at greater risk 
of extirpation due to stochastic natural events than were 
metapopulations, but the analysis was not rigorously quantitative. We 
have also indicated that climatic variables play a role and that YCT 
subpopulations on the margins of the range are naturally at greater 
risk due to those factors.
    Kruse et al. (2001) assessed the possible demographic and genetic 
consequences of purposely isolating the populations of YCT in headwater 
streams in the Absaroka Mountains, Wyoming. Such isolation may result, 
for example, from intentional placement of a movement barrier to 
prevent nonnative fishes downstream from invading upstream reaches. 
Kruse et al. (2001) speculated that isolated YCT populations are 
vulnerable to chance extinction, although they also pointed out that 
``there has been little opportunity to observe the real effects of 
small population size and isolation on native, extant Yellowstone 
cutthroat trout populations.''
    The widespread geographic distribution of YCT across the 
subspecies' range in portions of five States further mitigates 
potential negative effects resulting from local population extinctions 
following future catastrophic natural events, as no single event is 
likely to impact a significant percent of the overall number of 
isolated populations. Moreover, given the widespread efforts for the 
conservation of these fish, any such local extirpation that occurs in 
habitat where YCT are precluded from naturally recolonizing is likely 
to be followed by reintroduction efforts by responsible management 
agencies. There is widespread evidence of successful establishment of 
reproducing populations of YCT in suitable vacant habitat, often from a 
single introduction, as witnessed by the many self-sustaining 
populations of YCT found in lakes upstream from geological barriers 
that precluded their natural colonization.
    Information provided in the YCT status assessment report (May et 
al. 2003) indicated that, although 143 (73 percent) of the 195 YCT 
conservation populations were isolets that were often restricted to 10 
stream miles or less habitat in isolated headwater areas, those isolets 
represented only 27 percent of the total stream miles occupied by YCT. 
Thus, the small YCT populations in headwater areas are numerous, but 
they collectively occupy only about \1/4\ of the total habitat occupied 
by YCT conservation populations. Most of the occupied stream miles (73 
percent) were habitat for YCT in metapopulations. As a result of this 
analysis (USFWS 2006), we conclude that the fragmentation and isolation 
of small YCT populations in headwater areas has not resulted in the 
subspecies being eliminated from major portions of its historical 
Threats to Any of the Three Yellowstone Cutthroat Trout Life-History 
    Three life-history forms occur across the range of YCT. We found 
that YCT naturally occur in an unquantified but small number of lakes 
(probably fewer than 20) across the range. All of the natural YCT 
populations dependent on lakes are considered adfluvial (i.e., live in 
lakes and migrate into rivers to spawn) and most of them are in areas 
where they receive a high level of habitat protection afforded by 
national parks or wilderness. However, YCT with the adfluvial life 
history constitute a small proportion of the range of YCT and did so 
    The State of Wyoming, in comments submitted for this status review 
(Wichers 2005), indicated that YNP is an important part of Wyoming and 
plays a significant role in YCT conservation but expressed concern that 
the importance of YNP to overall YCT

[[Page 8828]]

conservation should not be overstated. Wichers (2005) reported that of 
the entire historic stream habitat in Wyoming, 88 percent is outside 
YNP and 80 percent of the currently occupied stream miles are outside 
YNP. Based on May et al. (2003), YNP accounts for about 4.7 percent of 
the historic and 8.5 percent of the presently occupied miles of habitat 
across the entire range of YCT. However, we note that Yellowstone Lake 
constitutes the majority of existing habitat for the adfluvial life 
history form. The significance of this is discussed in greater detail 
in the status review (USFWS 2006).
    We also found that stream-dwelling resident (i.e., showing little 
movement) and fluvial (i.e., migratory within streams and larger 
rivers) YCT populations constitute the most common YCT life-history 
forms and occur in well over 90 percent of the estimated 12,115 km 
(7,528 mi) of occupied habitat distributed among two major stream 
drainages (Snake and Yellowstone) and 40 component watersheds. The 
distinction between resident and fluvial migratory forms is often 
difficult to discern in practice and there is considerable overlap, so 
it is not possible to definitively quantify the occupied distribution 
of each of these two life history forms. Over the long term, 
preservation of all existing life history forms is important to 
persistence of YCT. The inherent life form plasticity of the subspecies 
and its proven ability to colonize new habitats (i.e., history of fish 
culture success) would appear to provide some measure of security for 
perpetuation of the adfluvial life history form, which is the most 
vulnerable form, into the future.
Fisheries Management
    Historic introductions of nonnative species by the Federal 
Government, State fish and game departments, and private parties, 
across the West have contributed to declines in abundance, local 
extirpations, and hybridization of YCT (Gresswell 1995; Kruse et al. 
2000; Dunham et al. 2004). In addition, legal and illegal activities 
associated with recreational angling are known to be a major vector for 
movement and dispersal of nonnative fishes and other organisms (Hagener 
2005). The unauthorized or unintentional movement of nonnative 
organisms poses a significant but unquantifiable risk associated with 
recreational angling.
    The States have policies in place to combat these concerns. For 
example, the Private Pond Stocking Policy of MFWP restricts what 
species of fish may be stocked in private ponds that are in YCT-
occupied drainages of Montana (Hagener 2005). In Wyoming, State Game 
and Fish Commission policy precludes the stocking of fish into waters 
that are capable of sustaining satisfactory, self-sustaining fisheries 
(WGFD 2005). Other States have similar policies (see details in USFWS 
Competition From Introduced Brook Trout
    Brook trout, a char species native to eastern North America but 
liberally introduced throughout the West, beginning as early as 1900, 
can adversely compete with YCT (e.g., Griffith 1988). Brook trout 
apparently adapt better to degraded habitats than native trout and 
brook trout also tend to occur in streams with higher water 
temperatures (Adams and Bjornn 1997). Because elevated water 
temperatures and sediments are often indicative of degraded habitat 
conditions, native trout may be subject to compounded stresses from 
both competitive interactions with brook trout and degraded habitat 
(Rieman et al. 2006).
    The database of May et al. (2003) did not assess the extent that 
brook trout co-occur (i.e., are sympatric) with extant YCT. However, in 
future iterations of the database that information will be incorporated 
(Brad Shepard, MFWP, pers. comm. 2005). Nonetheless, it is evident from 
the longstanding coexistence of brook trout with YCT in some streams 
that complete competitive exclusion of YCT by brook trout is not 
necessarily inevitable where the two fishes co-occur.
    Systematic sampling of the Snake River headwaters in Wyoming 
(McAllister 2005) found brook trout were present in approximately 13 
percent of the length of all perennial streams occupied by any trout 
species or subspecies (but 27 percent of the streams themselves). Brook 
trout have displaced cutthroat trout from 14 streams that comprise 1.3 
percent of the total trout stream in that watershed. Ten of the 14 
streams sampled are tributaries to the Snake River.
    In the Teton River, Wyoming, YCT have experienced broad declines 
(Koenig 2005) and are seemingly being replaced by brook trout. Benjamin 
(2005) reported that only four drainages in the upper Teton River 
watershed remain inhabited solely by YCT. Benjamin (2005) hypothesized 
that these populations have probably been spared from invasion because 
culverts, diversion structures, and dewatered sections prevent fish 
from moving from the main Teton River into these tributaries. The nine 
largest tributaries in the upper Teton watershed that are occupied by 
YCT have been colonized by brook trout.
    Although a correlation exists between the spread of brook trout 
populations (or other nonnative salmonids) and the decline of YCT in 
some watersheds, the causes of YCT population decline often include 
multiple currently operating factors (e.g., habitat loss, dewatering, 
whirling disease, etc.). As a result, it is difficult to determine 
whether brook trout are the cause of YCT decline in such cases or 
merely a symptom of broader ecosystem perturbations (Rieman et al. 
2006). We conclude that the competition from introduced brook trout is 
serious, where it occurs, but it has not affected the status of YCT 
conservation populations on a widespread scale. Comprehensive analysis 
of the degree of rangewide overlap between YCT and brook trout 
distribution is currently not available, but is expected to be a 
component of the next iteration of the State status assessment.
Hybridization With Nonnative Fishes
    Hybridization with introduced, nonnative fishes, particularly 
rainbow trout and their hybrid descendants that have established self-
sustaining populations, is recognized as an appreciable threat to YCT 
conservation. The YCT is known to interbreed primarily with rainbow 
trout and to a lesser extent with other subspecies of cutthroat trout. 
Rainbow trout were first stocked into many regions of the historic 
range of YCT more than 100 years ago. May et al. (2003) estimated that 
133 of the 195 designated conservation populations (68 percent) would 
meet the standard as ``core conservation population,'' essentially 
containing nonintrogressed YCT. These 133 potential ``core conservation 
populations'' occupy 3,009 km (1,870 mi) of habitat, encompassing about 
29 percent of the approximately 10,223 km (6,352 mi) of habitat that 
May et al. (2003) considered to be occupied by conservation 
    As pointed out by May et al. (2003), the vulnerability to 
hybridization of YCT in metapopulations stems from the key 
characteristic of the metapopulation itself, i.e., the ability of its 
member fish to move (and interbreed) among the various YCT populations 
that constitute the metapopulation. It is assumed that potentially 
hybridizing fishes are similarly unencumbered in their movements 
throughout the geographic area occupied by the metapopulation and, 
accordingly, YCT metapopulations can inevitably become completely 
introgressed as a hybrid swarm. However, as the following discussion

[[Page 8829]]

shows, the process of hybridization and the results of introgression 
are not always predictable.
    In Idaho, YCT in many populations are sympatric with potentially 
hybridizing rainbow trout but remain nonintrogressed (Meyer et al. 2006 
in review). Thus, the occurrence of potentially hybridizing fishes does 
not portend their imminent hybridization with YCT. A multitude of 
factors, both physical and biological, determine whether or not 
introgression may occur, and those factors may not be stable over time. 
For example, in some circumstances drought cycles may serve to isolate 
spawning populations of YCT, possibly limiting access to potentially 
introgressing fish in YCT habitat. However, in other cases drought 
could have the opposite effect by limiting YCT access to traditional 
spawning streams where spatial or temporal isolation historically 
occurred; thereby forcing fish to spawn together in greater proximity 
and contributing to increased introgression.
    In the Yellowstone River in Montana, De Rito (2004) assessed 
whether spatial or temporal reproductive isolation, or both, occurs 
between YCT and nonnative rainbow trout. Time and place of spawning 
were determined by radiotelemetry of 164 trout (98 cutthroat, 37 
rainbow, and 29 cutthroat x rainbow hybrids) over 3 spawning seasons, 
from 2001 to 2003. Spawning area and spawning-reach overlap were high 
among all taxa. In contrast, mean migration and spawning dates of 
rainbow trout and hybrids were 5 to 9 weeks earlier than for cutthroat 
trout. Rainbow trout and hybrids began migrating and spawning in April 
and May when Yellowstone River discharges were lower and water 
temperatures were colder. In contrast, cutthroat trout migration and 
spawning occurred in June and July, when discharges and temperatures 
were higher. De Rito (2004) concluded that difference in time of 
spawning is likely the predominant mechanism eliciting reproductive 
isolation. He further concluded that conservation actions that focused 
on protecting and enhancing later spawning cutthroat trout in 
tributaries may enhance temporal reproductive isolation from rainbow 
trout and their hybrids.
    There are scattered populations of WCT or other nonnative cutthroat 
trout subspecies found within the range of YCT, as a result of past 
introductions. However, due to the widespread popularity of fish 
culture activities using YCT, the opposite pattern (e.g., YCT stocked 
in the native range of WCT) is a much more common occurrence. The 
present hybridization risk to YCT is almost entirely from rainbow 
    In most cases today, it is not technologically possible to 
eliminate the self-sustaining populations of potentially hybridizing, 
nonnative fishes from entire drainages or even individual streams. 
Consequently, perceived threats to extant YCT posed by nonnative fishes 
in streams are sometimes met by installing barriers to the upstream 
movement of the nonnative fishes into stream reaches occupied by core 
populations of nonintrogressed YCT. In a few cases, usually involving 
small streams that provide the greatest opportunity for success, fish 
toxins may be used to completely remove all fishes upstream from such 
barriers, after which YCT may be stocked (Caswell and Huffaker 2005; 
Hagener 2005; Lewis 2005; WGFD 2005). Because of technological, 
budgetary, and other limitations, actions to eliminate or isolate 
sources of introgression are now being taken for only a small 
proportion of YCT populations across the subspecies' range.
    Self-sustaining populations of nonnative rainbow trout pose the 
greatest hybridization threat to YCT and few of those populations can 
be eliminated or appreciably reduced. A key concern becomes the extent 
that introgressive hybridization may eventually pervade existing 
nonintrogressed or suspected nonintrogressed YCT populations, 
particularly those that inhabit headwater streams in high-elevation 
    Meyer et al. (2003) found that YCT hybridization with rainbow trout 
in the Upper Snake River basin is far from ubiquitous, with only 19 
percent of the sites containing YCT also containing rainbow trout or 
hybrids (see additional discussion in USFWS 2006). The finding that 
hybridization is not widespread across the Upper Snake River basin 
comports with range-wide findings of May et al. (2003) for YCT.
    In addition, many extant YCT populations occur upstream from 
natural barriers that prevent the existing upstream movement of 
nonnative fishes, including those that may potentially hybridize with 
YCT. We examined the database of May et al. (2003) to determine the 
extent that nonintrogressed or suspected nonintrogressed YCT 
populations occur upstream from such ``complete'' barriers. Results 
indicated that a little over 3,219 km (2,000 mi) of stream habitat 
occupied by YCT conservation populations, including about 748 km (465 
mi) inhabited by YCT in the 143 isolated populations and about 2,585 km 
(1,606 mi) inhabited by YCT in metapopulations are upstream from 
barriers. Of these, a high proportion is populated by nonintrogressed 
YCT with no hybridizing rainbow trout or other species in proximity.
    The observation that numerous nonintrogressed YCT populations 
persist today despite the longstanding sympatric occurrence (i.e., more 
than 100 years) of potentially hybridizing fishes, or their presence in 
downstream reaches where the absence of barriers to the upstream 
movement of those fish occurs, corroborates the physical evidence that 
not all nonintrogressed YCT populations have been and are equally 
vulnerable to introgression. The threat of hybridization with nonnative 
rainbow trout and the potential for introgression to occur to such an 
extent as to compromise the integrity of conservation populations of 
YCT is a complex and still evolving dynamic process. While we do not 
discount this threat and believe it may present one of the single 
biggest challenges to the continued conservation of YCT, we are 
encouraged that the most recent scientific studies (e.g., Meyer et al. 
2003, De Rito 2004, Novak et al. 2005, Meyer et al. 2006 in review) 
indicate that substantial genetic isolation of YCT may persist, even in 
sympatry with populations of rainbow trout. These data would appear to 
indicate that the level of genetic isolation has not been increasing.
New Zealand Mud Snails
    New Zealand mud snails (NZMS), an invasive nonnative mollusk, can 
coat benthic/food producing areas, has not been found in any areas 
currently occupied by wild populations of YCT in Wyoming (WGFD 2005). 
In 2002, NZMS were discovered in the Big Horn River (Upper Big Horn 
HUC) near Thermopolis, Wyoming. High densities of NZMS exist in Polecat 
Creek, a tributary to the Snake River near the YNP boundary. Polecat 
Creek is a geothermally heated stream, which likely contributes to the 
high densities of NZMS observed. NZMS can be found in the Snake River 
above Jackson Lake, but in lower densities than in Polecat Creek. No 
additional information on the range or spread of NZMS within the 
conservation habitat of YCT was reviewed. While it is likely this 
organism is increasingly becoming more widespread and will continue to 
spread, to date there is no evidence that implicates NZMS in the 
collapse of any conservation populations of YCT.

[[Page 8830]]

Summary of Factor E
    As a result of our status review (see USFWS 2006), we conclude the 
best scientific and commercial information available indicates that 
risk associated with fragmentation and isolation of small YCT 
conservation populations, including stochastic risk from catastrophic 
natural events, has not affected the status of YCT to the extent that 
listing under the ESA as a threatened or endangered species is 
    The available data also do not suggest the future loss of any of 
the three life-history forms represented by YCT, although the adfluvial 
form is clearly the most vulnerable. We conclude the best scientific 
and commercial information available to us indicates that threats to 
any of the three YCT life-history forms have not affected the status of 
the YCT to such an extent that listing under the ESA as a threatened or 
endangered species is warranted.
    In our 90-day finding (66 FR 11244) we concluded that ongoing 
fisheries management programs were not a sufficient threat to the 
status of YCT to cause us to consider listing. Likewise, the presence 
of introduced, nonnative fishes such as brook trout did not necessarily 
portend the imminent decline or elimination of YCT. This status review 
(see USFWS 2006) supports that conclusion.
    As a result of this analysis, we also conclude the best scientific 
and commercial information available to us indicates that introgressive 
hybridization with rainbow trout or other cutthroat subspecies has not 
affected the status of YCT to the extent that listing under the ESA as 
a threatened or endangered species is warranted. However, we will 
continue to evaluate new information that may be made available 
regarding these and other threats, and we urge the public to submit to 
us any new information that becomes available concerning the status of 
or threats to YCT. That is particularly true of new threats such as the 
recent spread of invasive New Zealand mud snails.

Petition Finding

    In the context of the ESA, the term ``threatened species'' means 
any species (or subspecies or, for vertebrates, DPS) that is likely to 
become an endangered species within the foreseeable future throughout 
all or a significant portion of its range. The term ``endangered 
species'' means any species that is in danger of extinction throughout 
all or a significant portion of its range. The ESA does not indicate 
threshold levels of historic population size at which, as the 
population of a species declines, listing as either ``threatened'' or 
``endangered'' becomes warranted. Instead, the principal considerations 
in the determination of whether or not a species warrants listing as a 
threatened or an endangered species under the ESA are the threats that 
now confront the species and the probability that the species will 
persist in ``the foreseeable future.'' The ESA does not define the term 
``foreseeable future.'' However, the YCT Interstate Workgroup that 
produced the YCT status assessment report (May et al. 2003) which 
formed much of the scientific basis for our status review (USFWS 2006) 
considered the ``foreseeable future'' to be 20 to 30 years (which 
equates to approximately 4 to 10 YCT generations, depending on the 
productivity of the environment). That is a measure that the USFWS 
supports as both reasonable and appropriate for our status review 
(USFWS 2006) because it is long enough to take into account multi-
generational dynamics of life-history and ecological adaptation, yet 
short enough to incorporate social and political change that affects 
species management.
    In our status review (USFWS 2006), we provided evidence that 
indicates a decline in YCT occurred over the past 200 years, but much 
of that loss is believed to have occurred in the late 19th and early 
20th century. Recent trends appear to be stable or upward, with a few 
notable exceptions (i.e., Yellowstone Lake, Teton River). Although YCT 
remain widely distributed in two headwater basins, the overall 
abundance of YCT have declined to an undetermined extent over the past 
two centuries (May et al. 2003). We attribute the distributional 
decline of YCT in large measure to competition, hybridization, and 
predation caused by one or more nonnative fish species. These impacts 
have been observed since the initial introductions of brown trout, 
rainbow trout, and brook trout began in the late 1800s. These 
introduced salmonid species have subsequently expanded to colonize new 
habitat and form many naturally reproducing populations occupying the 
range of YCT. More recently, lake trout introduction has been a major 
factor in causing decline of the adfluvial YCT population of 
Yellowstone Lake.
    Coinciding with, and largely inseparable in its effect on YCT from 
the impacts of nonnative species introduction, has been a gradual and 
in some instances substantial decline in overall quality of in-stream 
fish habitat and riparian status. This has occurred largely as a result 
of human-caused land and water management practices. Increased sediment 
and reduced or altered streamflow patterns are considered the primary 
causes of reduced habitat quality for native salmonid populations 
throughout the west. These impacts have probably been exacerbated by 
natural or man-caused climate changes that have led to generally warmer 
and drier conditions. Such conditions generally do not favor cutthroat 
trout, especially in watersheds occupying the margins of suitable 
habitat within their historical range.
    Our analysis for this review (USFWS 2006) found there is little 
evidence of major changes in overall distribution or abundance of YCT 
over approximately the past decade. There are indications that 
increased focus is being placed by management agencies on the 
protection and restoration of conservation populations of YCT in many 
watersheds. Corresponding emphasis is occurring on habitat restoration 
activities and fisheries management actions such as restrictive angling 
regulation changes that are designed to benefit YCT. For many of these 
actions, it is too early to judge their success. Some of these actions 
appear to have resulted in improved population levels in some areas. 
Examples are found in the Snake River Headwaters of Wyoming (Novak et 
al. 2005), portions of Idaho (Meyer et al. 2003; Meyer et al. 2006 in 
review), the Shields River watershed in Montana (Hagener 2005), and 
other locations. At the same time, this success is countered by 
evidence of recent dramatic declines in a formerly robust population of 
YCT within the relatively secure habitat of Yellowstone Lake in YNP 
(Koel et al. 2005), documented declines and recruitment failure in the 
Teton River watershed in Wyoming and Idaho (Benjamin 2005; Koenig 
2005), and concerns over the status and threats due to selenium 
toxicity in the Blackfoot River and possibly other watersheds in Idaho 
(Lemly 1999; Christensen 2005). In balance, the monitoring record is 
insufficient to document either an overall upward or downward trend in 
the status of YCT populations across the subspecies' historic range 
over the recent past.
    It is important that the status and distribution of YCT continue to 
be monitored. The USFWS finds that the management agencies are 
contributing substantial resources in that regard, and we believe the 
planned upgrade of the YCT status assessment to be initiated by the 
Yellowstone Cutthroat Trout Interstate Workgroup in 2006 (WGFD 2005; 
Brad Shepard, MFWP, pers. comm. 2005) will become an important

[[Page 8831]]

document for establishing an accurate current baseline to be used to 
evaluate future population status changes.


    On December 17, 2004, Judge Figa (U.S. District Court of Colorado) 
ordered the USFWS to complete a 12-month status review for YCT. As a 
result, we have done so and present our conclusions in this notice, and 
in more detail in the accompanying status review (USFWS 2006). The 
information we have summarized includes substantial amounts of new 
information not analyzed or reported in our previous 90-day finding (66 
FR 11244), particularly that obtained from the status report of May et 
al. (2003). That information indicates at least 195 extant YCT 
conservation populations, qualifying as YCT under the standards we have 
adopted, collectively occupy 10,220 km (6,352 mi) of stream and lake 
habitat in Idaho, Montana, Wyoming, Utah, and Nevada. Those 195 YCT 
populations are distributed among 35 component watersheds in the Snake 
and Yellowstone River basins, within the international boundaries of 
the United States.
    Of those 195 conservation populations, about 133 were considered 
likely to qualify as potential ``core conservation populations'' 
comprised of nonintrogressed YCT (99 percent genetic purity standard; 
see Discussion of Hybrid YCT in Listing Determinations at the beginning 
of the status review [USFWS 2006]). If, after further genetic testing 
the existence of approximately 133 core conservation populations is 
verified, then those populations would include about 3,009 km (1,870 
mi) of habitat encompassing about 29 percent of the existing range of 
conservation populations of YCT.
    Although the distribution of YCT has been reduced from historic 
levels and existing populations face threats in several areas of the 
historic range, we find that the magnitude and imminence of those 
threats do not compromise the continued existence of the subspecies 
within the foreseeable future (which we define as 20-30 years). Many 
former threats to YCT, such as those posed by excessive harvest by 
anglers or the ongoing stocking of nonnative fishes, are no longer 
factors that threaten the continued existence of YCT. That is not to 
downplay the active legacy of past fish stocking activities, but 
current programs have been revised to avoid further impacts. The 
effects of other extant threats, especially those to habitat, may be 
effectively countered, at least in part, by the ongoing management 
actions of State and Federal agencies. These actions occur in 
conjunction with application of existing regulatory mechanisms. It is 
largely too soon to judge the overall long-term effectiveness of those 
actions, though some positive signs are present. At the least, we 
conclude that active loss of habitat has been minimized.
    Nonetheless, hybridization with nonnative rainbow trout or their 
hybrid progeny and descendants, both of which have established self-
sustaining populations in many areas in the range of YCT, remains an 
active threat in the form of introgression to YCT conservation 
populations. The eventual extent that hybridization occurs in YCT 
habitat may be stream-specific and impossible to predict. Nonetheless, 
the criteria that we adopted for inclusion of individual fish or 
populations as YCT, following the lead of past actions (see WCT finding 
in USFWS 2003; 66 FR 46989) and consistent with the genetic standards 
adopted by the State fishery managers (Utah Division of Wildlife 
Resources 2000), allow for the limited presence in YCT conservation 
populations of genetic material from other fish species. We view this 
as consistent with the intent and purpose of the ESA.
    The YCT remain widely distributed and there are numerous robust YCT 
populations and metapopulations throughout the subspecies' historic 
range. Moreover, numerous nonintrogressed YCT populations are 
distributed in secure habitats throughout the subspecies' historic 
range. In addition, despite the frequent occurrence of introgressive 
hybridization, we find that some YCT populations that are sympatric 
with rainbow trout are nonintrogressed or nearly so, and thus retain 
substantial portions of their genetic ancestry, apparently due to 
temporal, behavioral, or spatial reproductive isolation. We consider 
slightly introgressed YCT populations, with low amounts of genetic 
introgression detectable only by molecular genetic methods, to be a 
potentially important and valued component of the overall YCT (i.e., 
``conservation populations'').
    Finally, the numerous ongoing YCT conservation efforts clearly 
demonstrate the broad interest in protecting YCT held by State, 
Federal, Tribal, local, and nongovernmental organizations and other 
entities. However, those ongoing conservation efforts, while important, 
are not pivotal to our decision whether or not to propose to list the 
YCT as either a threatened or an endangered species under the ESA. That 
decision is based mainly on the present-day status and trend of YCT, 
the mitigation of many of the existing threats, and the occurrence of 
the numerous extant laws and regulations that work to prevent the 
adverse effects of land-management and other activities on YCT, 
particularly on those lands administered by Federal agencies.
    On the basis of the best available scientific and commercial 
information, which has been broadly discussed in this notice and 
detailed in the documents contained in the Administrative Record for 
this decision, we conclude that the YCT is not endangered (threatened 
with extinction within the foreseeable future), nor is it threatened 
with becoming endangered within the foreseeable future. Therefore, 
listing of the YCT as a threatened or an endangered species under the 
ESA is not warranted at this time.

References Cited

    A complete list of all references cited herein is available upon 
request from the Field Supervisor at the Montana Ecological Services 
Office (see ADDRESSES).


    The primary author of this document is the Montana Ecological 
Services Office (see ADDRESSES).


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

    Dated: February 14, 2006.
H. Dale Hall,
Director, Fish and Wildlife Service.
[FR Doc. 06-1539 Filed 2-17-06; 8:45 am]