Federal Register / Vol. 73, No. 175 / Tuesday, September 9, 2008 / Proposed Rules 52235 

Dated: August 26, 2008. 

Michael K. Buckley, 

Deputy Assistant Administrator for 

Mitigation, Department of Homeland 

Security, Federal Emergency Management 

Agency. 

[FR Doc. E8–20823 Filed 9–8–08; 8:45 am] 

BILLING CODE 9110–12–P 

DEPARTMENT OF THE INTERIOR 

Fish and Wildlife Service 

50 CFR Part 17 

[FWS–R6–ES–2008–0023; 1111 FY07 MO–

B2] 

Endangered and Threatened Wildlife 

and Plants; 12-Month Finding on a 

Petition To List the Bonneville 

Cutthroat Trout as Threatened or 

Endangered 

AGENCY: Fish and Wildlife Service, 

Interior. 

ACTION: Notice of a 12-month petition 

finding. 

SUMMARY: We, the U.S. Fish and 

Wildlife Service (Service), announce our 

12-month finding on a petition to list 

the Bonneville cutthroat trout 

(Oncorhynchus clarkii utah) as a 

threatened subspecies throughout its 

range in the United States, pursuant to 

the Endangered Species Act of 1973, as 

amended (Act). After a thorough review 

of all available scientific and 

commercial information, we find that 

listing the Bonneville cutthroat trout 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 

conservation of the subspecies. 

DATES: The finding in this document 

was made on September 9, 2008. 

ADDRESSES: This finding is available on 

the Internet at http:// 

www.regulations.gov. Supporting 

documentation we used in preparing 

this finding is available for public 

inspection, by appointment, during 

normal business hours at the U.S. Fish 

and Wildlife Service, Utah Ecological 

Services Office, 2369 West Orton Circle, 

Suite 50, West Valley City, Utah 84119; 

telephone (801) 975–3330. Please 

submit any new information, materials, 

comments, or questions concerning this 

finding to the above address or via 

electronic mail (e-mail) at 

paul_abate@fws.gov. 

FOR FURTHER INFORMATION CONTACT: 

Larry Crist, Field Supervisor, U.S. Fish 

and Wildlife Service, Utah Ecological 

Services Office (see ADDRESSES section). 

If you use a telecommunications device 

for the deaf (TDD), call the Federal 

Information Relay Service (FIRS) at 

800–877–8339. 

SUPPLEMENTARY INFORMATION: 

Background 

Section 4(b)(3)(B) of the Endangered 

Species Act of 1973, as amended (Act) 

(16 U.S.C. 1531 et seq.), requires that, 

for any petition to revise the 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 species are 

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 Act 

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, that is, requiring a subsequent 

finding to be made within 12 months. 

Such 12-month findings must be 

published in the Federal Register. 

Previous Federal Actions 

On February 26, 1998, we received a 

petition, dated February 5, 1998, from 

the Biodiversity Legal Foundation 

requesting that the Service list the 

Bonneville cutthroat trout 

(Oncorhynchus clarkii utah) (BCT) as 

threatened in U.S. river and lake 

ecosystems where it continues to exist, 

and to designate its occupied habitat as 

critical habitat within a reasonable 

period of time following the listing. On 

December 8, 1998, we published a 90- 

day petition finding for the BCT in the 

Federal Register (63 FR 67640). We 

found that the petition presented 

substantial information indicating that 

the subspecies may be warranted for 

listing under the Act, and initiated a 

review of the subspecies’ status within 

its historic range. 

In the 1998 90-day finding, we 

solicited additional data, comments, 

and suggestions from the public, other 

governmental agencies, the scientific 

community, industry, and other 

interested parties concerning the status 

of the BCT throughout its range. The 

comment period for submission of 

additional information ended on 

January 7, 1999, but was reopened (64 

FR 2167) during January 13 through 

February 12, 1999. We published a 12- 

month finding in the Federal Register 

on October 9, 2001 (66 FR 51362), and 

documented that the BCT was not 

warranted for listing under the Act 

because it was neither endangered nor 

likely to become endangered within the 

foreseeable future throughout all or a 

significant portion of its range. 

On February 17, 2005, we were sued 

by the Center for Biological Diversity, 

and others, on the merits of the 12- 

month finding. On March 7, 2007, the 

District Court of Colorado dismissed the 

lawsuit after determining that Plaintiffs 

failed to demonstrate the not warranted 

finding was arbitrary, capricious, or 

contrary to law. The Plaintiffs appealed 

to the 10th Circuit Court of Appeals on 

May 4, 2007. 

On March 16, 2007, in the interim 

between the lawsuit dismissal and 

appeal, the Solicitor of the Department 

of the Interior issued a formal opinion 

regarding the legal interpretation of the 

term ‘‘significant portion of the range’’

of a species (DOI 2007). The opinion 

provides guidance on analysis intended 

to determine whether a species is in 

danger of extinction throughout a 

significant portion of its range when it 

is not in danger of extinction throughout 

its entire current range. Because this 

opinion was pertinent to the BCT 

decision, we withdrew the 2001 12- 

month finding for BCT (USFWS 2007, 

entire), and initiated a new status 

review to include significant portion of 

the range analysis. We published a 

notice in the Federal Register (73 FR 

7236) announcing the opening of a 

comment period from February 7 

through April 7, 2008. The notice 

specified that the new status review 

would include consideration and 

analysis of all information previously 

submitted, and any new information 

provided regarding the status of the 

BCT. 

Species Biology 

The BCT is native to the Bonneville 

basin, and is 1 of 14 subspecies of 

cutthroat trout recognized by Behnke 

(1992, pp. 3–21, 132–138) that are 

native to interior regions of western 

North America. BCT generally have 

large, evenly distributed spots, but a 

high degree of intra-basin variation 

exists. BCT tend to develop large, 

pronounced spots that are evenly 

distributed on the sides of the body 

rather than concentrated posteriorly as 

in the Yellowstone cutthroat trout 

(Oncorhynchus clarkii bouveri) 


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subspecies. Coloration in BCT is 

generally dull compared to other 

cutthroat subspecies; however, 

coloration can vary depending on 

environmental conditions and local 

genetic composition (Behnke 1992, pp. 

132–138). 

Vertebrae typically number 62–63, 

slightly higher than in other subspecies. 

Scales in lateral series average 150–170. 

BCT average between 16–21 gill rakers, 

with a mean of 18–19, except the Snake 

Valley type, which have 18–24 (mean, 

20–22). Another important 

characteristic of all cutthroat subspecies 

is the presence of basibranchial teeth, 

which are absent in rainbow trout 

(Behnke 1992, p. 132). Numbers of 

basibranchial teeth provide information 

about subspecies derivation and 

relatedness. The Snake Valley type have 

profuse basibranchial teeth, averaging 

20–28, while most other BCT average 5–

10 (Behnke 1992, p. 132). 

Life strategies exhibited by BCT 

include stream resident (occupy home 

ranges entirely within relatively short 

reaches of streams), fluvial (migrate as 

adults from larger streams or rivers to 

smaller streams to reproduce), adfluvial 

(migrate, sometimes many kilometers, as 

mature adults from lakes to inlet or 

outlet streams to spawn), and lacustrine 

(lake) forms. The life strategy that a 

particular BCT population exhibits 

likely depends on a combination of 

environmental conditions and genetic 

plasticity of inherited traits. Very little 

information is available to suggest the 

extent of plasticity and what 

environmental characteristics may cue a 

successful shift in life strategy. Most 

information is based on the success or 

failure of transplants of various life 

forms among different aquatic 

ecosystems. Furthermore, evidence 

suggests that BCT populations within a 

single stream can comprise multiple life 

history strategies (resident, fluvial, 

adfluvial), and that individuals may use 

mainstem rivers to move between and 

among drainages where they are not 

fragmented by water diversions or 

barriers (Kershner et al. 1997, entire). 

May et al. (1978, p. 19) found that 

male BCT sexually matured at age 2 

while females matured at 3 years of age. 

However, Bear Lake BCT were reported 

to mature much later, with adults 

normally beginning to mature at 5 years 

of age but not spawning until age 10 

(Neilson and Lentsch 1988, p. 131). 

Both the age at maturity and the annual 

timing of spawning vary geographically 

with elevation, temperature, and life 

history strategy (Behnke 1992, p. 136; 

Kershner 1995, pp. 28–30). Lake 

resident trout may begin spawning at 2 

years and usually continue throughout 

their lives, while adfluvial individuals 

may not spawn for several years 

(Kershner 1995, pp. 28–30). Annual 

spawning of BCT usually occurs during 

the spring and early summer at higher 

elevations at temperatures ranging from 

4–10 °C (May et al. 1978, p. 19). May et 

al. (1978, p. 19) reported BCT spawning 

in Birch Creek, Utah, beginning in May 

and continuing into June. BCT in Bear 

Lake began spawning in late April and 

completed spawning in June (Nielson 

and Lentsch 1988, p. 131). The wild 

broodstock at Manning Meadow 

Reservoir (9,500 feet elevation) spawn 

from late June to early July (Hepworth 

and Ottenbacher 1997, p. 1). In Lake 

Alice, Wyoming, fish were predicted to 

spawn from late May until mid-June 

(Binns 1981, p. 47). 

Fecundity of cutthroat is typically 

1,200–3,200 eggs per kilogram (kg) (2.2 

pounds (lbs)) of body weight (Behnke 

1992, p. 33). In Birch Creek, a 147 

millimeters (mm) (5.8 inches (in)) BCT 

female produced 99 eggs, a 158 mm (5.8 

in) female produced 60 eggs and a 176 

mm (6.9 in) female produced 176 eggs 

(May et al. 1978, p. 19). Whereas in 

Raymond Creek, Wyoming, 3 females 

ranging from 124 to 246 mm (4.9 to 9.7 

in) averaged 165 eggs (Binns 1981, p. 

48). Evidence suggests fecundity of lakedwelling BCT is greater. Fecundity of 

females in Lake Alice averaged 474 

eggs/female (Binns 1981, p. 48), while 

females in Manning Meadow, Utah, 

averaged 994 eggs/female (D. Hepworth, 

Utah Division of Wildlife Resources, 

unpubl. data). Incubation times for wild 

BCT have not been verified, but Platts 

(1957, p. 10) suggested eggs hatch and 

fry begin to emerge approximately 45 

days after spawning, depending on 

temperature. 

Larvae typically emerge in mid-to-late 

summer, depending on spawning times. 

Once emerged, larvae or fry, as they are 

commonly called, are poor swimmers 

and typically migrate to stream margins. 

Adfluvial BCT spend 1 or 2 years in 

streams before migrating to the Lake 

(Nielson and Lentsch 1988, p. 131). 

Growth of resident BCT is highly 

dependent on stream productivity. In 

general, growth of trout tends to be 

slower in high-elevation headwater 

drainages than in lacustrine 

environments, but this likely depends 

on temperatures and food base. In Birch 

Creek, Utah, age 1 fish averaged 84 mm 

(3.3 in), age 2 fish averaged 119 mm (4.7 

in), age 3 fish averaged 158 mm (6.2 in), 

and age 4 fish averaged 197 mm (7.8 in) 

in length (May et al. 1978, p. 17). 

Growth in two Wyoming streams was 

faster, and age 4 fish averaged 282 to 

320 mm (11.1 to 12.6 in) in length 

(Binns 1981, p. 44). In contrast, BCT in 

Bear Lake grow to an average size of 560 

mm (22.0 in) and 2 kg (4.4 lbs) (Nielson 

and Lentsch 1988, p. 131). Historic 

accounts of BCT in Utah Lake suggest 

fish may have reached a meter in length 

(Notes from Yarrow and Henshaw in 

1872 as described by Tanner 1936). 

Platts (1957, p. 10) reported that some 

BCT taken from Utah Lake a century ago 

attained weights of over 11.3 kg (25 lbs). 

Little is known about feeding habits of 

BCT. In general, BCT trout are 

insectivorous, especially in stream 

habitats. Both terrestrial and aquatic 

insects appear to be important to their 

diet (May et al. 1978, pp. 7–10; Binns 

1981, p. 48). In Birch Creek, May et al. 

(1978, pp. 9–10) reported BCT diets 

were diverse in summer, while in the 

fall in Trout Creek, Utah, their diet 

consisted primarily of terrestrial insects. 

Dipterans and debris were the dominant 

food items for immature trout, while 

terrestrial insects were the dominant 

prey for mature individuals. BCT may 

display more plasticity in feeding habits 

depending on the system or specific 

population characteristics. Little 

information has been collected on BCT 

to understand the extent of feeding 

shifts of BCT. Platts (1957, p. 4) 

suggested that cutthroat do not need to 

feed on fish to attain large sizes but will 

do so where insects are not abundant. 

Interactions With Nonnative Fish 

BCT may or may not persist when 

nonnative trout are stocked into BCT 

waters. The actual mechanism that 

dictates the survivorship of BCT in the 

presence of nonnatives is unknown, but 

the recent discovery that numerous BCT 

populations have persisted for decades 

in the presence of rainbow trout 

(Oncorhynchus mykiss), Yellowstone 

cutthroat trout, and other nonnatives 

suggests BCT is not always displaced by 

nonnatives as previously thought. 

However, BCT can hybridize with 

rainbow trout and Yellowstone 

cutthroats in some situations and be 

displaced by the superior competitor, 

brook trout (Salvelinus fontinalis). The 

degree of hybridization appears to vary 

with the persistence of the stocked fish 

and also with habitat conditions as does 

the level of competition with brook 

trout. 

Benhke (1992, p. 107) reported that 

BCT native to the Bear River drainage 

adapted to the harsh and fluctuating 

environments of desert basin streams, 

remaining the dominant trout today in 

many streams where nonnative trout 

were introduced. This seems to be a 

fairly unique trait of BCT compared to 

other cutthroat subspecies. There is still 

no specific rationale as to why BCT 

would persist better than other desert 


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cutthroat subspecies, yet something in 

its unique genetic composition seems to 

allow BCT to persist where other 

cutthroat subspecies have been found to 

be displaced. 

For example, Bear Lake BCT, probably 

due to the unique environmental 

conditions in which they developed, 

have resisted hybridization with and 

replacement by nonnative trout. 

Yellowstone cutthroat trout, 

Yellowstone cutthroat rainbow trout 

hybrids, and rainbow trout were 

consistently stocked into Bear Lake for 

decades. Benhke (1992, p.137) 

examined specimens from Bear Lake 

and compared these to museum 

specimens from the lake and with 

cutthroat trout from the Bear River 

drainage and found no evidence of 

hybridization among their taxonomic 

characters. Nielson and Lentsch (1988, 

p.130) similarly reported that, after 

examining the DNA of 52 Bear Lake 

specimens, no rainbow trout alleles 

were observed in any fish. 

Since the early 1990’s, many 

additional remnant BCT populations 

have been found in streams that had 

been stocked with rainbow trout or 

Yellowstone cutthroat trout (Utah 

Division of Wildlife Resources, 

unpublished data). These BCT 

populations were assumed to be lost 

through hybridization until recent 

surveys found BCT present. Results of 

these surveys suggest BCT have retained 

much of their natural genetic integrity 

despite intensive nonnative stocking 

efforts. 

Introduced brook trout have been 

stocked, legally and illegally, into some 

BCT waters. BCT do not hybridize with 

brook trout, but brook trout are thought 

to acquire resources better and 

reproduce and recruit more efficiently 

than BCT. The specific mechanism of 

how brook trout displace BCT is 

unknown, but greater fecundity, earlier 

maturity, and tolerance of higher 

densities gives brook trout an advantage 

over the native BCT (Griffith 1988, p. 

105; Fausch 1989, pp. 307–312). The 

extent of threat to BCT from brook trout 

varies depending on environmental 

conditions of the stream. Although not 

considered the greatest threat to the 

persistence of BCT, competition from 

introduced brook trout can and has 

displaced native BCT populations. 

Habitat Requirements 

Trout, regardless of their evolutionary 

history, require 4 types of habitat during 

various stages of their life history: 

spawning habitat, nursery or rearing 

habitat, adult habitat, and overwintering 

habitat. Spawning gravels are required 

for spawning success and can be a 

limiting factor in high-gradient streams 

where the current carries off suitable 

spawning gravel (Behnke 1992, p. 25). 

Conversely, an even greater concern 

may be accumulation of fine sediments 

into interstitial spaces of spawning 

gravels, which prevents egg incubation 

and reduces larval survival. Such fines 

can become dominant in the sediments 

when poor land-use practices alter flow 

regimes, remove riparian vegetation, 

and/or degrade overall watershed 

conditions. These human-induced 

activities can aggravate already fragile 

soils and geology in vulnerable desert 

climates. 

Little information is available on 

specific habitat requirements for BCT; 

however, there is a wealth of 

information on salmonid habitat 

conditions in general which appear to 

generally represent those of BCT 

(Pennak and Van Gerpen 1947, entire; 

Binns and Eiserman 1979, entire; 

Scarnecchia and Bergersen 1987, entire). 

For example, well-oxygenated water, 

cooler temperatures in general and a 

complexity of instream habitat 

structure, such as large woody debris 

and overhanging banks, are considered 

good trout habitat conditions. For 

various species, subspecies, and local 

forms, adaptations and tolerance of 

these conditions varies. BCT have also 

been found to survive and be fairly 

robust in what is considered marginal 

salmonid habitat conditions (e.g., turbid 

water, fine sediments, warmer 

temperatures, poor structural habitat). 

This may be because BCT have evolved 

in a desert environment where climate 

can cause fluctuations in water and 

sediment regimes and environmental 

condition (Behnke 1992, p. 107). 

It was previously thought that with 

the exception of three lacustrine 

systems, Bear Lake (Utah and Idaho), 

Utah Lake, and Alice Lake (Wyoming), 

BCT were historically found in cool 

headwater streams throughout the 

Bonneville basin. However, more recent 

research and status and genetic surveys 

reveal BCT populations are found at 

high, moderate, and low elevations 

(within the range of elevations in the 

Bonneville Basin) in small headwater 

streams, such as those of the north slope 

of the western Uintas, to larger 

mainstem rivers, such as the Thomas 

Fork of the Bear River (UDWR, 

unpublished data). 

Historic Habitat 

BCT likely historically occupied all 

suitable habitats within the Pleistocene 

Lake Bonneville basin, which included 

portions of Idaho, Nevada, Utah, and 

Wyoming. The desiccation of ancient 

Lake Bonneville about 8,000 years ago 

likely fragmented the BCT into 

remaining streams and lakes throughout 

the basin, resulting in several slightly 

differentiated groups of BCT, including: 

(1) The Bear River basin; (2) the 

Bonneville basin proper, including the 

Wasatch Mountain and Sevier River 

drainages; and (3) the Snake Valley, an 

arm of ancient Lake Bonneville that was 

isolated during an earlier desiccation 

event (Behnke 1992, pp. 132–138). 

There is general consensus among the 

scientific community, including the 

Service, that all these groups represent 

the BCT subspecies (Shiozawa 2008, p. 

1). For the purposes of this finding, all 

three groups are considered BCT. 

The BCT Conservation Team, which 

includes biologists from Wyoming Game 

and Fish Department (WGFD), Utah 

Division of Wildlife Resources (UDWR), 

Nevada Division of Wildlife (NDOW), 

Idaho Department of Fish and Game 

(IDFG), Bureau of Land Management 

(BLM), U.S. Forest Service (USFS), the 

National Park Service (NPS), and the 

Service, completed a status report (May 

and Albeke 2005) that describes the 

rangewide status of BCT in the United 

States. The rangewide status report 

summarized the best available 

information on BCT (May and Albeke 

2005, pp. i, 16, 103–104). The status 

report was peer reviewed by five 

recognized experts in the fields of 

fishery biology, conservation biology, 

and genetics. The peer reviewers found 

that the status report provided sound 

scientific data to use in this 12-month 

finding. 

The 2001 finding on Bonneville 

Cutthroat Trout included 28,863 

hectares (71,322 acres) of lake habitat 

(indicated as an adfluvial life history) 

(USFWS 2001, pp. 34, 44, 50, 75). The 

2005 BCT rangewide status report relied 

on a protocol that was not designed to 

address lake populations; however, 8 

lakes connected to occupied stream 

habitat were included as 412 stream 

kilometers (km) (256 stream miles (mi)) 

(May and Albeke 2005, pp. 107, 110, 

120). Thus, throughout the remainder of 

the document, all occupied BCT habitat 

is reported as stream habitat and 

includes lake populations. These lake 

populations are an important 

component in conserving BCT, and 

some lakes are specifically designated to 

preserve genetically pure populations 

(Donaldson 2008, pp. 8–9). 

The BCT Conservation Team’s status 

report included an analysis of probable 

historic distribution (May and Albeke 

2005, pp. 6, 16–19). Our understanding 

of BCT historic distribution is based on 

habitat thought to be occupied around 

1800. The determination of occupation 

in this era was based on historic 


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climactic conditions, stream channel 

gradient, barriers that would preclude 

fish, and expertise of fishery biologists 

familiar with each watershed. The 

analysis resulted in 10,876 (km) (6,758 

mi) of stream habitat potentially 

occupied historically (May and Albeke 

2005, pp. 6, 16–19). This analysis 

included estimated stream miles for 

historically occupied BCT lakes because 

the analysis protocol was not designed 

to address lake populations separately. 

The historically occupied habitat 

identified in each State included: 

Utah—7,916 km (4,919 mi) (73 percent); 

Idaho—1,854 km (1,152 mi) (17 

percent); Wyoming—974 km (605 mi) (9 

percent); and Nevada—132 km (82 mi) 

(1 percent) (May and Albeke 2005, pp. 

6, 16–19). The United States is divided 

and sub-divided into successively 

smaller hydrologic units that are 

classified into four levels: regions, subregions, accounting units, and 

cataloging units. Fourth-level 

hydrologic unit codes (HUCs) in the 

Lake Bonneville Basin, including Pine 

Valley, Tule Valley, Pilot-Thousand 

Springs, Northern Great Salt Lake 

Desert, Lower Beaver, and Sevier Lake, 

were not included as historical habitats 

because they were judged unsuitable 

due to extreme conditions, because 

information on them prior to 1800 is 

unavailable, or because historical 

records indicate that they were devoid 

of fish. 

Current Distribution 

Current distribution of BCT is 

approximately 3,830 km (2,380 mi)—35 

percent of the probable historically 

occupied stream miles (May and Albeke 

2005, p. 19). Currently occupied habitat 

identified in each State includes Utah—

2,438 km (1,515 mi) (64 percent); 

Idaho—869 km (540 mi) (23 percent); 

Wyoming—476 km (296 mi) (12 

percent); and Nevada—47 km (29 mi) (1 

percent) (May and Albeke 2005, p. 19). 

The BCT is well distributed 

throughout its range in four watershedbased GMUs (see Figure 1; Table 1 

below). In earlier assessments, five 

GMUs or GUs (geographic units) were 

identified as including current 

populations of BCT; however, we 

combined the Bear Lake and Bear River 

GMUs because they occur within one 

watershed, and our analysis was 

conducted by watershed (May and 

Albeke 2005, pp. 4–5). This 

reconfiguration of GMUs does not imply 

a reduction in the geographic area 

where BCT occur (May and Albeke 

2005, pp. 2–5). 

Within each GMU, streams were 

identified to the 4th-level hydrologic 

unit and assigned to a HUC. BCT 

occupy habitat in 22 of the 23 HUCs 

determined to likely have supported 

historical habitat. BCT also occupy 

habitat in three HUCs that are either 

partially or totally outside of the 

subspecies historic range (May and 

Albeke 2005, pp. 19–20); most of these 

populations were reintroduced into 

suitable habitat with no record of 

nonnative fish (Behnke 1992, pp. 134–

135). The Bear River GMU has the 

greatest extent of currently occupied 

BCT habitat (2,010 km/1,249 mi), 

followed by the Northern Bonneville 

(1,532 km/952 mi), Southern Bonneville 

(187 km/116 mi), and the West Desert 

(101 km/63 mi). 

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TABLE 1—FROM MAY AND ALBEKE 2005, (P. 19), TABLE 21 (P. 34) 

GMU name Km (mi) currently 

occupied by BCT 

Number of BCT 

conservation 

populations 

Km (mi) occupied 

by BCT 

conservation 

populations 

Bear River .................................................................................................................. 2,010 (1,249) 33 1,753 (1,089) 

Northern Bonneville ................................................................................................... 1,532 (952) 65 1,318 (819) 

Southern Bonneville ................................................................................................... 187 (116) 21 145 (90) 

West Desert ............................................................................................................... 101 (63) 34 101 (63) 

Totals .................................................................................................................. 3,830 (2,380) 153 3,316 (2,061) 

Hybridization 

Hybridization is a concern for many 

cutthroat trout populations. An 

introgressed population results when a 

nonnative species or subspecies is 

introduced into or invades native 

cutthroat trout habitat, the two species 

then interbreed (i.e., hybridize), and the 

resulting hybrids survive and 

reproduce. If the hybrids backcross with 

one or both of the parental species, 

genetic introgression occurs. 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. 

Our criteria for considering the 

potential impact of introgressed 

populations of BCT are consistent with 

a position paper, titled ‘‘Genetic 

Considerations Associated with 

Cutthroat Trout Management,’’

developed by the fish and wildlife 

agencies of the intermountain western 

States (UDWR 2000a, pp. 1–9). 

Signatories to the position paper 

include the IDFG, Montana Fish 

Wildlife and Parks, NDOW, New 

Mexico Game and Fish Department, 

UDWR, and WGFD. The document 

identified, for all subspecies of inland 

cutthroat trout, three tiers of natural 

populations for prioritizing 

conservation and management options 

under State fish and wildlife 

management authorities: (1) Core 

conservation populations composed of 

greater than 99 percent cutthroat trout 

genes; (2) conservation populations that 

generally ‘‘have less than 10 percent 

introgression, but in which 

introgression may extend to a greater 

amount depending upon circumstances 

and the values and attributes to be 

preserved’’; and (3) cutthroat trout sport 

fish populations that, ‘‘at a minimum, 

meet a species’’ phenotypic expression 

defined by morphological and meristic 

characteristics (counts of body parts) of 

cutthroat trout.’’

The premise of the position paper on 

genetic considerations was that 

populations must conform, at a 

minimum, to the morphological and 

meristic characteristics of a particular 

cutthroat trout subspecies in order to be 

included in a State’s conservation and 

management plan for that subspecies. 

Conservation populations of a cutthroat 

trout subspecies include fish believed to 

have uncommon or important genetic, 

behavioral, or ecological characteristics 

relative to other populations of the 

subspecies. Sport fish populations, 

conversely, while conforming 

morphologically (and meristically) to 

the scientific taxonomic description of 

the subspecies, do not meet the 

additional genetic criteria of 

conservation or core, and are managed 

for their value as sport fish rather than 

for conservation of the subspecies. 

Following the State management 

agencies’ position paper (UDWR 2000a, 

pp. 1–9), a ‘‘core population’’ is 

genetically unaltered (pure), and a 

‘‘conservation population’’ is pure (a 

core population) or slightly introgressed 

(typically less than 10 percent) due to 

past hybridization, yet has attributes 

worthy of conservation. Therefore, 

conservation populations include both 

core populations (genetically pure) and 

populations that are less than 10 percent 

introgressed with rainbow trout or other 

subspecies of cutthroat trout (May and 

Albeke 2005, p. 71). The BCT rangewide 

status report (May and Albeke 2005, p. 

31) identified 153 stream populations 

(3,316 km/2,061 mi) as conservation 

populations (see Table 1, above, and 

Figure 2). Of the 153 conservation 

populations, 73 (732 km/455 mi) are 

considered core populations containing 

genetically pure BCT. 

We consider all core and conservation 

populations, as defined under the 

States’ standards and as described by 

May and Albeke (2005, p. 31), for 

purposes of conducting this status 

review. Because the categories are 

nested (conservation populations 

include core populations), we refer to 

them collectively as ‘‘BCT conservation 

populations’’ in the remainder of this 

finding. Some of the data presented in 

May and Albeke (2005) pertains to all 

BCT populations (including sport fish) 

or habitat. Those areas of this document 

that do not specify ‘‘conservation 

populations,’’ therefore, are referring to 

all BCT populations. We conducted our 

analysis on conservation populations 

because we found that BCT with less 

than 10 percent introgression still 

express important behavioral, life 

history, or ecological adaptations of 

indigenous populations within the 

range of the subspecies, and remain 

valuable to the overall conservation and 

survival of the subspecies (Campton and 

Kaeding 2005, pp. 1323–1325). (See also 

Factor E, Hybridization with Nonnative 

Fishes.) 

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Conservation Populations 

Designated BCT conservation 

populations exist throughout the 

subspecies’ historic range (May and 

Albeke 2005, p. 31)—in all four States 

and in the four designated GMUs. BCT 

currently occupy some habitat in 22 of 

the 23 HUCs historically occupied, and 

BCT that meet the conservation 

population definition (less than 10 

percent introgressed) exist in 19 of those 

HUCs. BCT conservation populations 

were also identified in two HUCs 

(Spring-Steptoe and Hot Creek-Railroad 

Valley) outside historic range, and three 

additional conservation populations 

were identified outside historical range 

within the Upper Virgin HUC. The 

majority of conservation populations 

(65) occur in the Northern Bonneville 

GMU occupying 1,318 km (819 mi). The 

remainder of BCT conservation 

populations are relatively equally 

distributed among the West Desert (34), 

Bear River (33), and Southern 

Bonneville (21) GMUs. These 

populations occupy 101 km (63 mi), 

1,753 km (1089 mi), and 145 km (90 mi) 

respectively (May and Albeke 2005, p. 

34). 

The majority of BCT conservation 

populations (101; 66 percent) occur as 

isolated, non-networked populations 

(May and Albeke 2005, p. 34); 25 

populations (16 percent) are weakly 

connected; 15 populations (10 percent) 

are moderately connected; and 12 

populations (8 percent) have migratory 

forms and open migration corridors that 

make them strongly connected. The 

strongly connected populations occur in 

Utah, Idaho, and Wyoming in the Bear 

River Geographic Management Unit 

(GMU) and Northern Bonneville GMU 

(May and Albeke 2005, pp. 34, 107, 115, 

117). 

BCT Population Trend 

BCT population trend and status can 

be interpreted from results of previous 

assessments conducted from the early 

1970’s through the present time. 

Hickman (1978, pp. 121–122) identified 

approximately 15 populations he 

considered ‘‘pure’’ occupying 

approximately 34 km (21 mi) of stream 

habitat. Duff (1988, pp. 121–127) 

reported 41 ‘‘genetically pure’’ BCT 

populations (39 stream populations) in 

association with 304 km (189 mi) of 

stream habitat. A draft Service status 

review that was never finalized reported 

48 genetically pure BCT populations 

throughout the Bonneville Basin 

(USFWS 1993, pp. 1–62). Duff (1996, 

pp. 38–39) further refined his BCT 

population distribution reporting 81 

genetically ‘‘pure’’ populations 

occupying 377 km (234 mi) of stream 

habitat. A Service status review found 

that BCT occupied a total of 1,372 km 

(852 mi) of stream habitat and 28,352 ha 

(70,059 acres) of lake habitat totaling 

291 populations (USFWS 2001, pp. iv–

v). 

BCT assessments conducted between 

1978 and 1996 generally counted 

populations that were thought to be 

genetically ‘‘pure.’’ The 2001 Service 

assessment determined the genetic 

status of each population but was more 

inclusive and counted management, 

conservation, and potential 

conservation populations (USFWS 2001, 

pp. viii–xi). The May and Albeke (2005) 

assessment assessed the genetic status of 

each BCT population and then 

categorized genetic status based on the 

criteria in the State’s genetic position 

paper (UDWR 2000a, pp. 1–9). 

Methods for tallying the number of 

individual BCT populations tended to 

vary by individual assessment, with 

earlier assessments tending to split 

tributary populations from mainstem 

river reaches. In contrast, methods used 

for the May and Albeke (2005, p. 64) 

assessment tended to group populations 

by higher order streams, thereby 

reducing the total count of populations. 

Thus, it is important to consider 

changes in the amount of occupied 

habitat when assessing population 

trends from different assessments rather 

than to simply rely on changes in 

number of populations. The number of 

known stream miles occupied by BCT 

conservation populations increased over 

time from 15 populations in 34 km (21 

mi) of habitat in 1978 to 153 

populations in 3,316 km (2,061 mi) in 

2004. Some of the increase in BCT 

conservation populations and their 

habitat is the result of conservation 

actions such as the discovery of more 

populations in recent years; the 

expansion or restoration of populations; 

and the eligibility of populations for 

conservation status (through genetic 

testing) that were previously considered 

hybridized. Increases in the amount of 

BCT conservation population habitat is 

also due to the use of a more accurate 

GIS-based assessment method that 

incorporated the National Hydrography 

Dataset geodatabase (May and Albeke 

2005, p. 2) and also the inclusion of 

lakes as river miles as used in the most 

recent assessment protocol (see above), 

although the increase due to the 

inclusion of lakes in the river mile 

calculation only accounts for an 

additional 412 km (256 mi) of stream 

habitat. 

The BCT Conservation Team’s most 

recent analysis of the number of BCT 

conservation populations and the extent 

of their habitat indicates that 

conservation populations have 

increased from 153 populations in 3,316 

km (2,061 mi) in 2004 (May and Albeke 

2005, p. 31), to 172 populations in 3,333 

km (2,071 mi) in 2008 (Burnett 2008a, 

entire). This most recent evaluation of 

the BCT Conservation Team’s database 

was cursory and was not performed for 

other population parameters discussed 

in May and Albeke (2005) (i.e., 

restoration activities, genetic status, 

population health and densities, etc.); 

however, it does indicate that the 

number of BCT conservation 

populations and their habitat continue 

to increase. 

Summary of Factors Affecting the 

Species 

Section 4 of the Act (16 U.S.C. 1533), 

and implementing regulations at 50 CFR 

424, set forth procedures for adding 

species to the Federal Lists of 

Endangered and Threatened Wildlife 

and Plants. In making this finding, we 

summarize information regarding the 

threats to the BCT in relation to the five 

factors provided in section 4(a)(1) of the 

Act. 

In making this finding, we considered 

all scientific and commercial 

information that we received or 

acquired up to the publication of the 

2001 12-month finding (66 FR 51362), 

and after publication of the notice 

initiating this finding (73 FR 7236; 

February 7, 2008). We relied primarily 

on published and peer-reviewed 

documentation for our conclusions, and 

most significantly, the rangewide status 

report competed by the BCT 

Conservation Team (May and Albeke 

2005, entire). 

Pursuant to section (4) of the Act, a 

species may be determined to be an 

endangered or threatened species on the 

basis of any of the following five factors: 

(A) Present or threatened destruction, 

modification, or curtailment of habitat 

or range; (B) overutilization for 

commercial, recreational, scientific, or 

educational purposes; (C) disease or 

predation; (D) inadequacy of existing 

regulatory mechanisms; or (E) other 

natural or manmade factors affecting its 

continued existence. We evaluated 

whether threats to the BCT may affect 

its survival. Our evaluation of threats, 

based on the best scientific and 

commercial information available, is 

presented below. 

Factor A. The Present or Threatened 

Destruction, Modification, or 

Curtailment of the Species’ Habitat or 

Range 

Land use activities associated with 

each BCT conservation population were 


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identified and documented in May and 

Albeke (2005, p. 52, Table 30), but the 

significance of the activities was not 

determined in relation to individual 

populations or to the conservation of the 

subspecies. Non-angling recreation 

(camping, hiking, ATV use, etc.) occurs 

in 69 percent of the conservation 

populations. Livestock grazing occurs in 

58 percent of the conservation 

populations, roads in 69 percent, timber 

harvest in 20 percent, and dewatering in 

30 percent. Hydroelectric plants, water 

storage, or flood control occurs in 20 

percent of the conservation populations. 

A small percentage of populations have 

mining or nonnative fish stocking. Many 

populations have more than one land 

use occurring in the area. 

A comprehensive assessment of the 

effects of land management practices on 

BCT does not exist. However, an 

evaluation of habitat quality was 

conducted for currently occupied 

habitat (May and Albeke 2005, p. 26). 

The evaluation considered both natural 

habitat features and human-caused 

disturbances. A stream ranked as 

‘‘excellent’’ if it had ample pool habitat, 

low sediment levels, optimal 

temperatures, and quality riparian 

habitat. A ‘‘good’’ habitat quality rating 

indicated the presence of some less than 

ideal attributes, and ‘‘fair’’ indicated the 

presence of a greater number of less 

than ideal attributes. A ‘‘poor’’ habitat 

quality rating indicated the inferior 

conditions of most habitat attributes. Of 

total occupied habitat for all BCT 

populations, excellent habitat 

conditions occurred in approximately 

196 km (122 mi) (5 percent); good 

conditions occurred in 1,801 km (1,119 

mi) (47 percent); fair conditions 

occurred in 1,080 km (671 mi) (28 

percent); poor conditions occurred in 

628 km (390 mi) (16 percent), and 

unknown conditions occurred in 126 

km (78 mi) (3.2 percent). The majority 

of occupied habitat (80 percent) is in 

fair, good, or excellent condition. 

Livestock grazing occurs in 58 percent 

of the BCT populations. Livestock 

grazing became an acute problem for 

watershed health in the late 1880s 

through 1930s when grazing, 

particularly sheep grazing, was so 

extensive and ill-managed that 

widespread watershed damage occurred 

throughout many areas in the 

Bonneville Basin. In fact, at the turn of 

the century, sheep were crowding cattle 

out of many areas (Peterson and Speth 

1980, p. 179). In the Wasatch Mountains 

east of Salt Lake City, Utah, over-grazing 

of sheep denuded mountain meadows, 

some to the extent that watersheds 

experienced massive soil loss, landslides and severe erosional damage. In 

addition to resident sheep, Utah was at 

a geographical ‘crossroads of the west’

where hundreds of sheep were trailed to 

and from neighboring States (Peterson 

and Speth 1980, p. 179). 

Overgrazing by sheep can be 

particularly damaging to overall 

watershed conditions. Sheep have been 

known to graze vegetation down to dirt 

and ‘‘grub’’ away at grass roots thereby 

damaging the soil mantle, which acts to 

hold water for plant uptake (Peterson 

and Speth 1980, p.180). The extensive 

watershed damage typical of overgrazing sheep in the early 20th century 

led to massive soil erosion, land slides, 

and flooding during heavy precipitation 

(Cottam 1947, pp. 23–29). Such events 

can completely eliminate local fish 

populations and undoubtedly affected 

local populations of BCT. For streams 

already fragmented from diversions or 

dewatering, such events could have led 

to local extirpation of BCT where no 

connected populations were available to 

recolonize streams after a catastrophic 

flood. 

Although cattle grazing can affect 

watershed conditions as well, the 

greater concern for cattle grazing stems 

from direct stream impacts where cattle 

are permitted to dwell in or are trailed 

through stream channels and riparian 

areas. Without adequate management, 

cattle can trample and destroy instream 

habitat and stream banks. They forage 

on lush riparian vegetation, which leads 

to degraded stream conditions and 

changes in channel morphology. 

Trampling destroys undercut banks 

resulting in wider and shallower 

channel morphology. Where this occurs, 

BCT can be impacted by increased water 

temperatures, loss of habitat complexity, 

altered macroinvertebrate food-base, 

and increased deposition of fine 

sediment (Platts 1991, p.393; Belsky et 

al. 1999, p.420; Rinne 1999, p.14). 

When livestock grazing is managed 

appropriately, it can occur in the 

vicinity of stream and riparian habitat, 

and habitat conditions that support fish 

populations can still be maintained 

(Fitch and Adams 1998, p. 197). The 

Western Watersheds Project, Inc. (Carter 

2008, pp. 1–7) submitted information 

documenting grazing impacts in 

localized areas in the Bear River GMU. 

Much of the information documents 

range conditions relative to grazing 

allotment reauthorizations. The 

information and conclusions presented 

included the assumption that, if a land 

management activity occurred within 

the vicinity of a BCT population, it was 

adversely affecting the population. We 

recognize that overgrazing can cause 

adverse impacts to individual 

populations of BCT. However, only 16 

percent of the occupied stream miles 

have poor habitat quality (May and 

Albeke 2005, p. 26). Specific 

information on grazing impacts to BCT 

habitat on a rangewide basis is not 

available. We found no information 

indicating that overgrazing significantly 

affects the rangewide status of BCT now, 

or will do so in the foreseeable future. 

Therefore, we conclude that overgrazing 

is not a significant threat to BCT. 

Roads, timber harvest, and dewatering 

occur in the area of some BCT 

populations. Similar to water 

development and grazing, the greatest 

impacts from timber harvesting 

occurred from 1850 to 1950. Although 

timber harvesting still occurs on 

National Forest Lands and very limited 

private lands in the Bonneville Basin, 

and may have some detrimental impacts 

on streams and watersheds, timber 

harvesting standards have substantially 

improved, particularly regarding 

protection of streams and watershed 

condition, and the catastrophic 

destruction that occurred in the first 100 

years of pioneer settlement no longer 

occurs. 

Currently, timber harvesting affects 

BCT through the indirect effects of road 

building and deforestation. Road 

building is known to add fine sediment 

to streams where roads cross or follow 

stream channels. These fine sediments 

can fill interstitial spaces important for 

successful spawning and survival of 

eggs and larval fish as well as alter the 

macro-invertebrate food base (Williams 

and Mundie 1978, p.1032–1033). 

Deforestation can also add sediment 

input into streams where riparian 

buffers are not implemented. Loss of 

trees also increases water volume 

draining into stream channels, which 

can alter flow and sediment regimes or 

exacerbate catastrophic flooding during 

extreme precipitation events. 

Within the Bonneville Basin, timber 

harvesting is fairly limited compared to 

other areas of the inland west, mainly 

because the arid climate is not 

conducive to extensive, lush forests. 

Timber harvest occurs in only 20 

percent of BCT conservation population 

habitat (May and Albeke 2005, p. 52, 

Table 30). We found no information 

indicating that timber harvesting 

significantly affects the rangewide status 

of BCT now, or will do so in the 

foreseeable future. Therefore, we 

conclude that timber harvesting is not a 

significant threat to BCT. 

Direct effects of water diversions and 

depletions (dewatering) on BCT occur 

where reaches are dewatered or made 

inaccessible by instream barriers. 

Secondary effects of water development 

may include higher water temperatures 


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in summer months because of lower 

water volume and diminished riparian 

condition and altered instream and 

shoreline habitat, all of which can 

impact cutthroat trout spawning and 

populations (Clancy 1988, pp. 40–41). 

Dewatering occurs in only 30 percent of 

BCT conservation population habitat 

(May and Albeke 2005, p. 52, Table 30). 

Rates of habitat loss through water 

diversions and depletions were likely 

heaviest for the decades immediately 

after pioneer settlement, in the late 

1800s, throughout the Bonneville Basin 

near locations of population growth. We 

found no information indicating that 

dewatering significantly affects the 

rangewide status of BCT now, or will do 

so in the foreseeable future. Therefore, 

we conclude that dewatering is not a 

significant threat to BCT. 

Idaho and Nevada have no producing 

oil or gas wells in BCT areas. However, 

oil and gas development has been 

accelerating over the last several years 

in Utah and Wyoming. Oil and gas 

development could affect BCT through 

increased land disturbance from roads 

and pads that could cause water quality 

problems associated with increased 

sediment loads, and through leaks, 

spills, and discharge of produced water 

reaching BCT habitat (WGFD 2004, pp. 

25–26). The BLM and Utah Division of 

Oil Gas and Mining provided 

information on locations of existing 

active and inactive wells and oil and gas 

leases on BLM, USFS, and other lands 

where BLM has jurisdiction over the 

subsurface mineral rights within the 

BCT range in Utah and Wyoming (BLM 

2008a, entire; UDOGM 2008, entire). A 

well exists within 1.6 km (1 mi) or less 

of 26 BCT conservation populations (17 

percent of all conservation populations). 

Of these 26 populations, 2 were near 

active or producing wells; the wells near 

the remaining 24 populations were nonproducing and were shut-in, plugged 

and abandoned, or abandoned entirely 

for development. These non-producing 

wells have a greatly reduced likelihood 

of releasing oil and gas related 

contaminants into BCT habitat (BLM 

2008b, entire). Relatively little overlap 

exists between oil and gas development 

sites and BCT conservation populations. 

BCT populations typically occur at 

higher elevations where minimal oil and 

gas activity exists. An analysis of 

potential future oil and gas development 

for the States of Wyoming and Utah 

indicates that the majority of leases 

occur outside the historic range of BCT 

(BLM 2008b, entire). Potential impacts 

to BCT resulting from oil and gas 

development on Federal land are 

typically assessed through the National 

Environmental Policy Act (NEPA) 

review process; as a result, future effects 

should be disclosed and effects to BCT 

will have to be taken into consideration 

due to the sensitive species management 

status of BCT on Federal land. 

Therefore, based on the best scientific 

and commercial information available, 

we conclude that dewatering is not a 

significant threat to BCT now, or in the 

foreseeable future. 

Summary of Factor A 

Land use practices, such as livestock 

grazing, road construction and 

maintenance, dewatering, and timber 

harvest, are occurring to some extent in 

most areas of occupied habitat. 

However, habitat quality ratings are fair, 

good, or excellent in 80 percent of BCT 

habitat throughout the current range of 

the subspecies. Approximately half of 

all BCT populations (49 percent) occur 

on Federal lands where land use 

regulations are in place to ensure 

ongoing maintenance of existing habitat 

(see Factor D). Restoration and 

conservation activities are occurring for 

at least 57 percent of the conservation 

populations. 

We find that the presence alone of an 

activity within a stream segment 

containing a conservation population is 

not sufficient evidence to conclude that 

the population is threatened or that a 

certain land use activity affects all 

populations rangewide at a significant 

level. Additional parameters, such as 

magnitude of impacts, distribution and 

abundance of BCT populations, and 

population trends, lend to an overall 

status determination. Many species exist 

in managed landscapes; not all are 

significantly impacted by human-caused 

influences to the level of being 

considered threatened under the Act. 

BCT conservation populations are 

well distributed in four GMUs, 

collectively forming a solid basis for 

persistence of BCT. These GMUs 

contain 19 of the 23 HUCs determined 

to have supported historical BCT 

habitat. In addition, BCT conservation 

populations currently occupy habitat in 

three HUCs that are either partially or 

totally outside the subspecies’ historic 

range. 

Based on the best scientific and 

commercial information available, we 

conclude that BCT is not now or in the 

foreseeable future, threatened by 

destruction, modification, or 

curtailment of its habitat or range to the 

extent that listing under the Act as a 

threatened or endangered species is 

warranted at this time. 

Factor B. Overutilization for 

Commercial, Recreational, Scientific, or 

Educational Purposes 

No commercial harvest of BCT 

currently occurs, so only recreational 

angling could potentially result in 

overutilization. Data show that angling 

occurs in 60 percent of BCT 

conservation populations (May and 

Albeke 2005, p. 52). Utah, Idaho, and 

Wyoming have special regulations 

providing protection against overharvest of BCT. These special 

regulations include catch-and-release 

requirements, limited harvest, fishing 

closures, and tackle restrictions. In 

addition, the remote location of many 

BCT streams provides protection from 

heavy fishing pressure (NDOW 2006, p. 

S–28; Baker et al. 2008, p. 29; 

Donaldson 2008, p. 3). 

The State of Idaho implements several 

fishing regulations to manage potential 

angler impacts in State waters. For most 

streams able to support larger fish, bag 

limits are 2 fish greater than or equal to 

40 centimeters (cm) (16 in) in length. In 

smaller streams, where BCT typically do 

not exceed 30 cm (12 in), the general 

stream limit is 2 fish, and no size 

constraints exist. In other waters, 

seasonal angling restrictions or catchand-release-only regulations are 

implemented (IDFG 2008, pp. 3, 19). In 

Utah, several fishing regulations protect 

native cutthroat trout from 

overutilization. The State reduced trout 

bag and possession limits from eight 

fish to four, and imposed short-term 

fishing closures to protect native 

cutthroat trout (Donaldson 2008, p. 3). 

Wyoming implements angling 

restrictions, such as size limits, reduced 

bag limits, and tackle restrictions to 

protect BCT populations (WGFD 2008, 

p. 8). Many of Nevada’s BCT 

populations occur in remote areas, 

which provide protection from heavy 

fishing pressure (Baker et al. 2008, p. 

29). None of the four States considers 

angling, under their current regulations, 

to be a threat to the subspecies. 

Collection of BCT for scientific or 

educational purposes is controlled by 

strict State permitting processes that 

prevent excessive sampling throughout 

its range in Utah, Wyoming, Idaho, and 

Nevada. Collection of fish tissue for 

genetic sampling is conducted by 

nonlethal techniques (Rogers 2007, pp. 

1–3). 

Summary of Factor B 

No commercial harvest of BCT 

currently occurs. Only recreational 

angling could potentially result in 

overutilization. However, Utah, Idaho, 

and Wyoming have special regulations 


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providing protection against overharvest of BCT. Also, in our 2001 12- 

month finding (66 FR 51362), we 

concluded that angler harvest did not 

pose a significant threat to the 

continued existence of BCT, and we 

know of no new information during 

development of this finding to change 

this conclusion. Collection of BCT for 

scientific or educational purposes is 

controlled by strict State permitting 

processes throughout the range of the 

subspecies. Therefore, we conclude that 

the best scientific and commercial 

information available indicates that 

overutilization for commercial, 

recreational, scientific, or educational 

purposes is not a significant threat to 

BCT now, or in the foreseeable future. 

Factor C. Disease or Predation 

Disease 

The BCT Conservation Team 

evaluated disease in the BCT status 

report (May and Albeke 2005, pp. 11–

12, 40–42). Diseases considered had the 

potential to cause significant impacts to 

population health and included, but 

were not limited to, whirling disease, 

infectious pancreatic necrosis virus, and 

furunculosis. The BCT Conservation 

Team assessed risks based on proximity 

of disease-causing pathogens and their 

accessibility to a population. The 

majority of the populations (63 percent) 

have limited risk because disease and 

pathogens are not known to exist in the 

watershed, or a barrier blocks upstream 

fish movement. In general, isolated 

populations have less risk of 

catastrophic diseases. Fourteen 

populations (9 percent) are currently 

known to be infected with one of the 

identified diseases (May and Albeke 

2005, pp. 40–41). 

In recent years, whirling disease has 

become of great concern to fishery 

managers in western States. Whirling 

disease is caused by the nonnative 

myxosporean parasite, Myxobolus 

cerebralis. This parasite was introduced 

to the United States from Europe in the 

1950’s and requires two separate host 

organisms to complete its life cycle. Its 

essential hosts are a salmonid fish and 

an aquatic worm, Tubifex tubifex. 

Juvenile, sub-adult, and adult life stages 

of BCT have been shown to be 

susceptible to whirling disease in the 

Logan River, and some Logan River 

study sites exhibit a downward trend in 

BCT abundance (Budy et al. 2005, pp. 

xi-xiii). Despite this, BCT in the Logan 

River demonstrate high growth and 

survival rates and are generally in 

relatively good health. Logan River 

tributaries are important refuges from 

whirling disease-infected areas in the 

Logan mainstem (Budy et al. 2005, pp. 

xi-xiii). Tubifex tubifex is most 

abundant in areas of high 

sedimentation, warmer water 

temperatures, and low dissolved 

oxygen. Most populations of BCT occur 

in cold water stream habitats at high 

elevations, where Tubifex tubifex is less 

likely to be abundant. 

All four States have developed 

management activities to protect BCT 

populations from whirling disease. 

Though whirling disease is known to 

occur in some Nevada waters, it 

currently does not pose a threat to BCT 

populations because it occurs at low 

levels among BCT populations (NDOW 

2006, pp. S27). Regardless, Nevada is in 

the process of formalizing protocols for 

BCT reintroductions and transplants 

relating to disease certification and 

broodstock management (NDOW 2006, 

pp. S27, S32). Idaho has outlined 

several strategies to protect BCT 

populations from the negative effects of 

disease. Strategies include monitoring 

fish populations for disease, prohibiting 

importation of fish and wildlife that 

carry disease risk, and ensuring that 

stocking, translocation, and propagation 

of fish do not contribute to the 

transmission or introduction of diseases 

(IDFG 2008, p. 14). Utah has some of the 

most stringent fish disease laws in the 

United States, which do not allow the 

stocking of fish that test positive for 

whirling disease (Donaldson 2008, pp. 

4–5). UDWR is studying the effects of 

whirling disease in a portion of BCT 

occupied waters in Utah that have been 

infected (Donaldson 2008, p. 4). 

Wyoming has a policy of not stocking 

fish that test positive for Myxobolus 

cerebralis (WGFD 2008, p. 9). 

Predation 

Of the 153 conservation populations 

identified in the rangewide BCT status 

report, 97 (63 percent) had no 

interaction with nonnative fish and 56 

(37 percent) were sympatric with 

nonnative fish (May and Albeke 2005, p. 

31). All BCT conservation populations 

sympatric with nonnative fish are 

located in the Bear River and Northern 

Bonneville GMUs. In these GMUs, BCT 

can be replaced by nonnative trout, but 

the degree to which predation is a factor 

in this replacement has not been well 

documented (Holden et al. 1997, pp. 3–

21). Although nonnative fish can have 

negative effects on BCT in localized 

areas due to predation, research in the 

Logan River drainage shows that it is 

possible for BCT populations to persist 

in the presence of predacious nonnative 

fish (Behnke 1992, p. 107; Budy et al. 

2005, pp. xi-xiii). 

Predation can affect BCT, mainly 

during early life stages, where other 

predaceous fish occupy the same area 

(UDWR 2000b, p. 48). Utah has 

implemented several management 

actions intended to alleviate potential 

predation of BCT by nonnative trout, 

including: nonnative removal/barrier 

installation projects; barring nonnative 

cutthroat stocking in conservation 

drainages; increasing angler harvest 

limits for brook trout in the Boulder and 

Uinta Mountains; and initiating 

fisheries research work (Donaldson 

2008, pp. 5–7). Nevada has virtually 

eliminated threats to BCT from 

nonnative fish by utilizing barriers and 

nonnative removal restoration projects 

(Baker et al. 2008, pp. 3–5; NDOW 2006, 

p. S–27). 

Similar to Utah, Idaho and Wyoming 

have enacted management actions 

intended to alleviate potential predation 

of BCT by nonnative trout. Idaho has 

discontinued stocking brook trout into 

native trout streams, increased the daily 

limit for brook trout from 6 to 25, and 

removed or suppressed nonnative trout 

species that compete with BCT (IDFG 

2008, pp. 6–7). Wyoming is monitoring 

BCT populations to ensure that 

nonnative populations do not become 

established in new waters in the Bear 

River drainage, have ceased stocking 

nonnative trout in waters managed for 

BCT conservation populations, and have 

implemented nonnative removal/barrier 

installation projects to control 

nonnative fish in BCT habitat (Emmrich 

2008, p. 2; WGFD 2008, p. 10). 

Summary of Factor C 

Only 14 (9 percent) BCT conservation 

populations are infected with a 

significant disease, and no additional 

populations are at high risk for infection 

(May and Albeke 2005, pp. 40–41). 

Therefore, we conclude that the best 

scientific and commercial information 

available indicates that neither whirling 

disease nor other disease organisms 

significantly threaten BCT now, or in 

the foreseeable future. 

Predation by nonnative fish, the 

primary source of predation on young 

BCT, may have some effect on BCT 

populations in the Bear River and 

Northern Bonneville GMUs. However, 

63 percent of conservation populations 

have no interactions with nonnative 

fish. Also, research shows that it is 

possible for BCT populations to persist 

in the presence of predacious nonnative 

fish (Behnke 1992, p. 107; Budy et al. 

2005, pp. xi–xiii). State fish and wildlife 

agencies continue to implement 

management actions intended to 

alleviate potential predation of BCT by 

nonnative fish. At this time, we know of 


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no information that indicates to us that 

predation significantly affects BCT now, 

or in the foreseeable future. 

Factor D. Inadequacy of Existing 

Regulatory Mechanisms 

The Act requires us to examine the 

adequacy of existing regulatory 

mechanisms with respect to extant 

threats that place the subspecies in 

danger of becoming either threatened or 

endangered. Regulatory mechanisms 

affecting BCT fall into three general 

categories: angling, land management, 

and water quantity. 

Angling 

The States of Utah, Idaho, Nevada, 

and Wyoming consider BCT a game 

species, and each State has specific 

regulations regarding catching BCT by 

angling. We concluded above that 

recreational angling is not a significant 

threat to BCT, now or in the foreseeable 

future (see Factor B). 

Regulatory Mechanisms Involving Land 

Management 

Numerous State and Federal laws and 

regulations help reduce adverse effects 

of land management activities on BCT. 

Most habitat in watersheds inhabited by 

BCT conservation populations is 

managed by Federal land management 

agencies, primarily the USFS and BLM, 

and to a limited extent the NPS. Federal 

laws that reduce impacts to BCT and 

their habitats include the Clean Water 

Act, Federal Land Policy and 

Management Act, National Forest 

Management Act, Wilderness Act, and 

National Environmental Policy Act. 

Approximately 49 percent of all 

occupied BCT habitat (including both 

sport fish and conservation populations) 

occurs on lands managed by Federal 

agencies, and the USFS manages the 

majority (May and Albeke 2005, p. 29). 

Of the 3,830 km (2,380 mi) of occupied 

habitat, 1,867 km (1,160 mi) are under 

Federal jurisdiction and the majority 

occur on National Forests (1,209 km 

(751 miles)) (May and Albeke 2005, p. 

29); these figures include sport fish 

populations because figures for 

conservation populations alone are not 

available (see Table 2 below). BCT occur 

in a large geographic area within the 

following National Forests: BridgerTeton, Caribou-Targhee, Dixie, Fishlake, 

Humboldt-Toiyabe, Uinta, and WasatchCache. BCT occupy 11 km (7 mi) of land 

administered by the BLM, and 7 km (4.4 

mi) managed by the NPS. 

Approximately 657 km (408 mi) of 

occupied BCT habitat occurs in 

wilderness areas managed by the USFS 

or BLM. Wilderness Areas and National 

Parks provide an extra level of 

protection for BCT because many land 

management activities are prohibited in 

them. 

TABLE 2—BCT OCCUPIED LAND OWNERSHIP

[Numbers include areas occupied by both sport fish and conservation populations] 

USFS BLM NPS 

USFS and 

BLM 

Wilderness 

Non-federal Total 

1,209 km .............................................................................. 11 km 7 km 657 km 2,603 km 3,830 km 

(751 mi) ................................................................................ (7 mi) (4.4 mi) (408 mi) (1,618 mi) (2,380 mi) 

U.S. Forest Service 

The USFS Sensitive Species Policy in 

Forest Manual 2670 outlines procedures 

for conserving sensitive species. The 

policy applies to projects implemented 

under the 1982 National Forest 

Management Act (NFMA). The range of 

the BCT is within USFS Region 4, where 

it is designated a sensitive species by 

the USFS, and where the Forests have 

Land and Resource Management Plans 

(LRMPs) developed under NFMA. The 

USFS has proposed a revision to NFMA 

in 2008; it is likely that, if the rule is 

finalized, LRMPs would be revised 

accordingly. The NFMA revision would 

result in more strategic and less 

prescriptive LRMPs that identify 

ecosystem-level desired conditions and 

provide management objectives and 

guidelines for meeting desired 

conditions (Forsgren 2008, pp. 1–2). The 

LRMPs might provide species-specific 

direction for special status species when 

broader, ecosystem-level desired 

conditions do not meet conservation 

requirements. 

USFS Manuals and Handbooks codify 

the agency’s policy, practices, and 

procedures and are sources of 

administrative direction for USFS 

employees. USFS Region 4 applies 

practices outlined in their Soil and 

Water Conservation Practices Handbook 

to BCT habitat (USFS 1988, pp. 1–71). 

This handbook states that the USFS will 

apply watershed conservation practices 

to sustain healthy soil, riparian, and 

aquatic systems. The handbook provides 

Management Measures with specific 

criteria for implementation. For 

example, Management Measure No. 

11.01 states: ‘‘The Northern and 

Intermountain Regions will manage 

watersheds to avoid irreversible effects 

on the soil resource and to produce 

water of quality and quantity sufficient 

to maintain beneficial uses in 

compliance with State Water Quality 

Standards.’’ Irreversible effects include 

reduced natural woody debris, excess 

sediment production that could reduce 

fish habitat, water temperature and 

nutrient increases that could affect 

beneficial uses, and compacted or 

disturbed soils that could cause site 

productivity loss and increased soil 

erosion. USFS land management 

practices are intended to avoid these 

effects whenever possible, while also 

providing for multiple-use mandates; 

therefore, maintaining or enhancing 

BCT habitat is being considered in 

conjunction with other agency 

priorities. We determined that USFS 

BCT management policies are currently 

adequately reducing impacts to the 

species; we found no information 

indicating that threats would rise to a 

significant level in the foreseeable 

future. 

Bureau of Land Management 

The BCT is designated a sensitive 

species by the BLM in Utah, Wyoming, 

Nevada, and Idaho. BLM policy offers 

the same level of protection for sensitive 

species as for candidate species. The 

policy in BLM Manual 6840—Special 

Status Species Management (BLM 2001, 

pp. 06A3–.06C1), reads as follows: ‘‘For 

candidate/sensitive species where lands 

administered by the BLM or BLM 

authorized actions have a significant 

effect on their status, manage the habitat 

to conserve the species by: 

(a) Ensuring candidate/sensitive 

species are appropriately considered in 

land use plans. 

(b) Developing, cooperating with, and 

implementing range-wide or sitespecific management plans, 

conservation strategies, and assessments 

for candidate/sensitive species that 

include specific habitat and population 

management objectives designed for 


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conservation, as well as management 

strategies necessary to meet those 

objectives. 

(c) Ensuring that BLM activities 

affecting the habitat of candidate/ 

sensitive species are carried out in a 

manner that is consistent with 

objectives for managing those species. 

(d) Monitoring populations and 

habitats of candidate/sensitive species 

to determine whether management 

objectives are being met.’’

BLM land management practices are 

intended to avoid negative effects to 

species whenever possible, while also 

providing for multiple-use mandates; 

therefore, maintaining or enhancing 

BCT habitat is being considered in 

conjunction with other agency 

priorities. We find that BLM BCT 

management policies are currently 

adequately reducing impacts to the 

species; we found no information 

indicating that threats would rise to a 

significant level in the foreseeable 

future. 

National Park Service 

When the Great Basin National Park 

(Park) was established in 1986, 

management of southern Snake 

Mountain Range streams was transferred 

from NDOW and the USFS to the NPS. 

The Park developed a Fisheries 

Management Plan in 1999 that included 

goals of reintroducing BCT into several 

area streams. In 1999, 40 km (24 mi) of 

stream habitat was unoccupied; due to 

restoration activities, 7 BCT 

conservation populations now exist in 

20 km (12 mi) of streams in and near the 

Park (Baker et al. 2008, pp. ii, 1). The 

Park will conduct long-term monitoring 

on the BCT populations and habitat. 

Most BCT waters within the Park are in 

remote, high-elevation locations where 

angling pressure is very light (Baker et 

al. 2008, pp. ii, 1). Livestock grazing, 

timber harvest, mining, and 

development do not occur in Great 

Basin National Park. We find that NPS 

management policies are currently 

adequately reducing impacts to the 

species; we found no information 

indicating that threats would rise to a 

significant level in the foreseeable 

future. 

Regulatory Mechanisms Involving Water 

Quantity 

Utah and Nevada control the 

implementation of instream flow 

regulations in BCT habitat. In Utah, the 

recent legislative session passed an 

instream flow bill (HB 117) that should 

benefit BCT by allowing private entities, 

such as Trout Unlimited, to lease 10- 

year water easements for instream flows 

(Donaldson 2008, p. 3). Wyoming has 

approved instream flow rights on 17 

stream segments encompassing 66 km 

(41 mi) of BCT habitat (WGFD 2008, p. 

8). We find that regulatory mechanisms 

regarding water policy are currently 

adequately protecting the species; we 

found no information indicating that 

threats would rise to a significant level 

in the foreseeable future. 

Conservation Actions 

State and Federal agencies are 

implementing existing programs to 

restore and enhance BCT habitat. The 

majority of the 153 conservation 

populations (57 percent) have one or 

more restoration, conservation, or 

management activities either completed 

or currently being implemented within 

BCT habitat (May and Albeke 2005, p. 

51). The WGFD adopted a Strategic 

Habitat Plan in 2001 (WGFD 2008, p. 6); 

under this Plan, habitat biologists work 

with landowners and land managers to 

manage habitat on a watershed scale to 

provide benefits to both terrestrial and 

aquatic wildlife resources. The States of 

Utah and Nevada have conservation 

agreements and conservation strategies 

involving review of BCT biology and 

monitoring of current subspecies status 

and potential threat factors (NDOW 

2006, pp. 1 to S–26; UBCTCT 2008, pp. 

1–23; UDWR 2008a, pp. 1–41). The 

State of Idaho has a Management Plan 

for Conservation of BCT in Idaho that 

provides conservation direction for BCT 

(Teuscher and Capurso 2007, pp. 1–84). 

The States of Utah, Nevada, 

Wyoming, and Idaho, and the USFS, 

BLM, NPS, Service, Confederated Tribes 

of the Goshute Reservation, and Utah 

Reclamation Mitigation and 

Conservation Commission are 

signatories to a rangewide conservation 

agreement and strategy for BCT. This 

agreement was implemented to ensure 

the long-term survival of the subspecies 

through coordination of conservation 

efforts among the signatory agencies 

(UDWR 2000b, pp. 1–90). 

Numerous conservation actions have 

been planned and implemented through 

State and Federal conservation and 

management plans. For example, the 

State of Utah (where the majority of BCT 

habitat and conservation populations 

exist) submitted two chronologies 

detailing BCT conservation efforts over 

two different time frames. BCT 

conservation actions were grouped from 

1973–2001 (approximately 378 actions) 

and from 2001–2008 (approximately 355 

actions); actions included, for example, 

population surveys and monitoring, 

genetic analysis, changes to angling 

regulations, broodstock development, 

fencing of stream habitat, establishment 

of conservation easements, nonnative 

fish removal and restocking with BCT, 

habitat surveys, stocking policy 

changes, and general habitat 

enhancement projects (UDWR 2008b, 

entire). These chronologies show that 

conservation actions were occurring 

prior to establishment of the State of 

Utah conservation programs in 2000, 

and that the number of conservation 

activities increased on a yearly basis 

(355 within 7 years) once these 

programs were enacted. Additionally, 

the BCT Conservation Team submitted 

information on State and Federal BCT 

conservation activities from 2001 

through 2007 in Utah, Wyoming, Idaho, 

and Nevada; activities are similar to 

those of the State of Utah described 

above (BCTCT 2008, entire). 

Under our Policy for Evaluation of 

Conservation Efforts When Making 

Listing Decisions (PECE) (68 FR 15100; 

March 28, 2003), we typically evaluate 

conservation efforts by State and local 

governments, and other entities, that 

have been planned but not 

implemented, or implemented but have 

not yet demonstrated effectiveness, in 

order to determine which efforts meet 

the standard in PECE for contributing to 

our finding. The actions described 

above were not analyzed using the PECE 

standard because they were 

implemented prior to this review and 

their effectiveness has been 

demonstrated by the general increases 

in BCT population numbers (as 

discussed in the BCT Population Trend 

section). State and Federal agency 

participation in BCT conservation plans 

is voluntary; however, the States 

included in the range of the BCT have 

a demonstrated history of effective 

management of the species. State plans 

are typically in place indefinitely or 

have a term of agreement for 5–10 years 

with renewal provisions for a similar 

time period. The rangewide BCT 

conservation agreement was renewed in 

2008 for 10 years, with the commitment 

that it would be extended for an 

additional 10 years upon expiration. 

The success of the conservation actions, 

as explained above, indicates that 

participating State and Federal agencies 

are committed to the conservation of 

BCT, and the renewal of the rangewide 

BCT agreement gives us a reasonable 

expectation that these efforts will 

continue in the foreseeable future. 

Summary of Factor D 

We assessed the potential threats of 

livestock grazing, timber harvest, roads, 

water management, mining, oil and gas 

developments, angling, disease, and 

predation with regard to magnitude of 

impacts to BCT, and to whether 

regulatory mechanisms are adequate. 


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We find that regulatory mechanisms 

related to land and fisheries 

management are currently sufficient for 

mitigating potential threats to BCT, and 

that the stable status of the species will 

continue in the foreseeable future. The 

best scientific and commercial 

information available indicates that 

existing regulatory mechanisms have 

maintained or improved the status of 

BCT to the extent that listing under the 

Act as a threatened or endangered 

species is not warranted. 

Factor E. Other Natural or Manmade 

Factors Affecting the Species’ Continued 

Existence 

Climate Change 

The Intergovernmental Panel on 

Climate Change (IPCC) has concluded 

that warming of climate is unequivocal 

(2007, p. 5), and that temperature 

increase is widespread over the globe 

and is greater at higher northern 

latitudes (IPCC 2007, p. 30). However, 

future changes in temperature and 

precipitation will vary regionally and 

locally, with some areas remaining 

unaffected or even decreasing in 

temperature (IPCC 2007, pp. 46–47). 

Changes in precipitation are less certain 

than in temperature; climate models 

project more frequent heavy 

precipitation events, separated by longer 

dry spells, especially in Utah and the 

western United States (GBRAC 2007, p. 

A1, 14–15; IPCC 2007, p. 15). 

During the past decade, the average 

temperature in Utah, like that of much 

of the globe, was higher than observed 

during any comparable period of the 

past century (IPCC 2007, pp. 31–32). As 

discussed below, that increase in 

temperature, if permanent, does not 

constitute a significant threat to the 

BCT. The remaining question is whether 

possible future increases in temperature 

will constitute a threat. Over the next 20 

years, climate models estimate that the 

Earth’s average surface temperature will 

increase about 1.4 °C (0.8 °F). Climate 

change predictions based on 

continental-scale analysis are generally 

given ranking based on degree of 

certainty (IPCC 2007, p. 27; GBRAC 

2007, pp. 3–11). Utah is projected to 

warm more than the global average 

(GBRAC 2007, pp. ES 2–3); however, 

levels of confidence in projections for 

local-scale areas are lower than for 

projections at global or continental 

scales, and are generally not given a 

degree of certainty ranking (GBRAC 

2007, pp. 17–20). Clear and robust 

future trends have not been developed 

for Utah (GBRAC 2007, p. 2). We cannot 

make reliable predictions about the 

magnitude or timing of future 

temperature increases within the range 

of the BCT. 

Based on the Utah Governor’s Blue 

Ribbon Advisory Council on Climate 

Change (2007), which is a regional 

study, climate change will likely cause 

environmental changes in Utah, which 

could increase challenges for BCT 

rangewide. According to some research, 

climate change has already had or is 

predicted to have negative 

consequences on coldwater fisheries 

globally (Nakano et al. 1996, p. 711; 

Hari et al. 2006, p. 24), and in the 

Southwest and Rocky Mountains of 

North America (Keleher and Rahel 1996, 

p. 1; Rahel et al. 1996, pp. 101, 102, 

113), through increases in ground- and 

surface-water temperatures. Rahel et al. 

(1996, p. 1116) and Keleher and Rahel 

(1996, p. 9) predicted that elevationally 

diverse regions such as the Rocky 

Mountains will experience warming 

stream temperatures that could restrict 

cold water species, such as cutthroat 

trout, to increasingly higher elevations, 

thus reducing the geographic range and 

occupied stream distance and increasing 

habitat fragmentation. Keleher and 

Rahel (1996, p. 5) calculated that in 

Wyoming a 1 °C (1.8 °F) increase in 

mean July air temperatures could 

decrease the length of streams 

inhabitable by salmonid fish by 8 

percent; a 2 °C (3.6 °F) increase could 

cause a reduction of 14 percent, a 3 °C 

(5.4 °F) increase could cause a 21 

percent decline, a 4 °C (7.2 °F) increase 

could cause a 31 percent reduction, and 

a 5 °C (9 °F) increase could cause a 43 

percent reduction. In the Rocky 

Mountains, Keleher and Rahel (1996, p. 

5) calculated similarly high reductions 

of 16.8, 35.6, 49.8, 62.0, and 71.8 

percent with respective temperature 

increases of 1, 2, 3, 4, or 5 °C in July 

air temperatures. One study concluded 

that if warming air temperatures occur, 

it will likely cause numerous 

fundamental environmental changes, 

including increased stream and lake 

temperatures, increased evaporation 

rates, reduced annual snowpack, 

changes in river flows, and increases in 

disturbance events such as floods, 

drought, and fire (Williams et al. 2007, 

p. 2). 

However, even if temperatures within 

the range of the BCT increased by the 

amounts considered in these studies, it 

would not put the species in danger of 

extinction. Bonneville cutthroat trout 

may be able to sustain viable 

populations at slightly warmer 

temperature conditions than other 

cutthroat trout subspecies. For example, 

Williams et al. (2007, p. 3) reported that 

less than 1 percent of the total 

distribution of westslope cutthroat trout 

and Colorado River cutthroat trout 

occurred in streams with an average July 

temperature greater than 22 °C (71.6 °F), 

but nearly 20 percent of the historical 

distribution of Bonneville cutthroat 

trout was associated with a mean July 

air temperature greater than 22 °C (71.6 

°F). In addition, Bonneville cutthroat 

trout appeared to be thermally 

distributed bimodally, with two peaks. 

The warmer second peak occurred due 

to an extensive network of lower 

elevation, warmer valley bottoms that 

were historically occupied (Williams et 

al. 2007, p. 3). Bonneville cutthroat 

trout have adapted to a broad spectrum 

of habitat conditions throughout their 

range (Kershner 1995, p. 28). 

Water temperature increases could 

result in a potential benefit to 

Bonneville cutthroat trout in localized 

areas. Cold summer water temperatures 

(mean July temperature of less than 7.8 

°C (46 °F)) have been found as a limiting 

factor to recruitment of cutthroat trout 

in high-elevation streams (Harig and 

Fausch 2002, p. 545; Coleman and 

Fausch 2007, pp. 1238–1240). 

Therefore, although climate change is 

likely to increase water temperatures 

and result in a reduction in habitat 

quality for lower elevation streams, 

some higher elevation streams may 

become more suitable for BCT. 

Declines in low-elevation mountain 

snowpack have been observed over the 

past several decades in the Pacific 

Northwest and California. However, no 

clear long-term snowpack trends are 

currently evident in Utah’s mountains 

(Hamlet et al. 2005, p. 4560; GBRAC 

2007, pp. A1, 1–2). Dates of peak snow 

accumulation and peak melt have also 

been trending earlier, but with the most 

notable differences occurring in coastal 

areas of the West that have warmer 

winter temperatures (Hamlet et al. 2005, 

p. 4560). Stewart et al. (2005, p. 1152) 

indicate that spring streamflow in the 

western United States during the last 5 

decades has shifted so that the major 

peak now arrives 1 to 4 weeks earlier, 

resulting in declining fractions of flow 

in the spring and summer. However, 

streamflows in Utah and the 

Intermountain West do not show clear 

trends over the past 50 years (GBRAC 

2007, p. A1, 10). 

In another study, three elements of 

environmental change expected to affect 

Western cutthroat trout as a result of 

climate change (increased summer 

water temperatures, flood events, and 

wildfire) were modeled to determine 

where a particular subspecies is likely 

to be at greatest risk (Williams et al. 

2007, pp. 2–5). The three elements were 

modeled individually, and then 

combined into a composite risk and 


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modeled jointly. Modeling showed that 

43 percent of sub-watersheds with 

existing BCT populations are at low or 

moderate risk from climate change, and 

57 percent are at high risk. The 

modeling also evaluated BCT 

populations in regional areas. The 

composite analysis showed that 

cutthroat populations in most of the 

Bear River basin and the eastern portion 

of the Northern Bonneville basins are 

likely at low risk from climate change, 

while the West Desert, Southern 

Bonneville, and Northern Bonneville 

basins are in the moderate to high-risk 

range (Williams et al. 2007, p. 6). 

A recent status review (73 FR 27899; 

May 14, 2008) for the Rio Grande 

cutthroat trout (Oncorhynchus clarkii 

virginalis) provided a comprehensive 

review of potential global and regional 

climate change effects to that 

subspecies. The status review provided 

detailed information regarding the 

potential effects of temperature change, 

decreased stream flow, change in 

hydrograph, and increases in extreme 

events. 

The Rio Grande cutthroat trout is 

native to the Rio Grande, Pecos, and 

Canadian River basins in New Mexico 

and Colorado (Behnke 2002, p. 219); the 

northern extent of this subspecies’ range 

lies at a more southerly latitude than the 

range of the Bonneville cutthroat trout. 

Therefore, predictions of the effects of 

climate change are likely to differ to 

some extent between the subspecies. 

One of the effects of climate change is 

that salmonid species are likely to be 

restricted to increasingly higher 

elevations or to more northern latitudes 

(Meisner et al. 1988, p. 6; Regier and 

Meisner 1990, p.11; Keleher and Rahel 

1996, p. 2; Nakano et al. 1996, pp. 716, 

717; Rahel et al. 1996, p. 1122; Poff et 

al. 2002, p. 7; Rieman et al. 2007, p. 

1558). Coldwater species occupying the 

southern distributions of their range, 

such as the Rio Grande cutthroat trout, 

are seen as more susceptible to 

extirpation as a consequence of global 

climate change (Poff et al. 2002, p. 8; 

Rieman et al. 2007, pp. 1552, 1553). 

Because Rio Grande cutthroat trout 

primarily occupy high-elevation 

headwater tributaries, dispersal to new 

habitats is unlikely because they 

currently occupy the uppermost 

available habitat (73 FR 27899; May 14, 

2008). In contrast, habitat for the 

Bonneville cutthroat trout is widely 

distributed and variable, ranging from 

high-elevation (3,500 m mean sea level) 

streams with coniferous and deciduous 

riparian trees to low-elevation (1,000 m 

mean sea level) streams in sage-steppe 

grasslands containing herbaceous 

riparian zones (Kerschner 1995; p. 28). 

BCT have adapted in order to survive in 

relatively warm water and marginal 

habitats, and migratory life forms 

historically grew to be quite large in 

lakes and large rivers. Some populations 

within the Bear River drainage in 

southern Idaho and northern Utah 

continue to exhibit the species’

impressive range of life history 

strategies and habitat requirements, 

migrating seasonally between turbid, 

lower elevation mainstem rivers and 

cold, clear, high-elevation tributary 

streams (Trout Unlimited 2008, entire). 

Climate change biological projections 

are based on effects models that have 

varying degrees of uncertainty (IPCC 

2002, pp. 14–16). For example, Williams 

et al. (2007, p. 6), in their modeling of 

climate change and western trout, used 

a 3 °C temperature increase (projected 

for the U.S. Pacific Northwest in this 

century based on a 2004 University of 

Washington Climate Impacts Group). It 

is unknown when the predicted 3 °C 

raise in temperature might be realized. 

Questions also remain regarding the 

projected extent of climate change 

across regional areas, the timeframe for 

temperature and precipitation changes, 

and the overall response of fish 

populations. It is unclear how climate 

change will interact with other 

environmental stressors at regional 

levels (IPCC 2002, p. 15). 

While climate change is likely to 

affect aquatic resources to some extent, 

including habitat utilized by BCT, at 

this time we find that these effects are 

not likely to cause significant long-term 

impacts to population viability. Current 

data indicate that the observed recent 

effects of climate change have had little 

significant impact on BCT population 

trends. BCT population trends show 

increasing numbers of conservation 

populations and increases in the 

amount of occupied river habitat, from 

15 populations in 34 km (21 mi) of 

habitat in 1978, to 153 populations in 

3,316 km (2,061 mi) in 2004 (May and 

Albeke 2005, p. 31; Hickman 1978, pp. 

121–122). Therefore, although climate 

change may cause some level of longterm effects to aquatic habitat, we find 

that climate change is not currently a 

threat to BCT, which have adapted to a 

broad spectrum of habitat conditions. 

We also find that climate change is not 

likely to significantly threaten the 

species rangewide within the 

foreseeable future. 

Fragmentation and Isolation of Small 

BCT Populations in Headwater Areas 

The majority of BCT conservation 

populations (101; 66 percent) occur as 

isolated, non-networked populations 

(May and Albeke 2005, p. 34); 25 

populations (16 percent) are weakly 

connected; 15 populations (10 percent) 

are moderately connected; and 12 

populations (8 percent) have migratory 

forms and open migration corridors that 

make them strongly connected. The 

strongly connected populations occur in 

Utah, Idaho, and Wyoming in the Bear 

River and Northern Bonneville GMUs 

(May and Albeke 2005, pp. 34, 107, 115, 

117). 

Cutthroat metapopulations are 

defined as a collection of localized 

populations that are geographically 

distinct but genetically interconnected 

through natural movement of individual 

fish between populations (UDWR 2000a, 

p. 8). Metapopulations are important 

because they maintain genetic exchange 

and increase genetic diversity. They also 

provide individuals to repopulate 

stream segments where populations are 

lost due to stochastic environmental 

events. Metapopulations are important 

to the overall status of the subspecies, 

but they are at a higher risk for disease 

and invasion of nonnative fish because 

these elements can move into any 

connected populations even if they are 

introduced into a single localized area. 

Problems associated with small, 

isolated cutthroat trout populations 

include increased risk of extirpation by 

catastrophic events and loss of genetic 

exchange. Isolated populations can also 

potentially be at risk of extirpation due 

to ongoing environmental forces causing 

changes in attributes such as habitat 

size, pool availability, or water 

temperatures. Several researchers have 

attempted to determine which 

environmental factors contribute to 

successful translocation efforts intended 

to augment isolated populations, and to 

integrate environmental factors into 

assessments of stream viability for 

cutthroat trout. Cold summer water 

temperature, narrow stream widths, and 

lack of deep pools can limit successful 

translocations of cutthroat trout (Harig 

and Fausch 2002, pp. 545–547). In highelevation streams, cold summer water 

temperatures can delay spawning and 

lack of deep-water pools can limit 

overwinter survival. Modeling of these 

stream variables indicates that occupied 

stream length is an even better predictor 

of cutthroat trout abundance than 

stream temperatures; small increases in 

habitat length (e.g., by barrier removal 

or rewetting of a dewatered stream 

segment) can produce a 

disproportionately greater increase in 

fish abundance, increasing viability of 

isolated populations (Young et al. 2005, 

pp. 2405–2406). 

A static model intended to describe 

the relationship between fish abundance 

and habitat is a tool for managers 


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implementing cutthroat trout restoration 

projects (Hildebrand and Kershner 2000, 

pp. 515–518). The model is especially 

useful in evaluating potential 

installation of artificial barriers to 

protect from nonnative fish invasion. 

Modeling indicated that a stream length 

of 3 km (2 mi) is required to support a 

population of 1,000 fish; 8 km (5 mi) 

supports 2,500 fish; and 17 km (10 mi) 

supports 5,000 fish. The model is not 

applicable in all situations; it 

incorporates several assumptions 

specifying that it is most relevant to 

isolated populations in streams less 

than 7 meters wide, and that food 

availability and habitat quality affect the 

relationship between fish abundance 

and stream length occupied. The 

relevance of the model for 

reintroduction and restoration of BCT 

populations should be carefully 

assessed, as small, isolated cutthroat 

trout populations have persisted for 

many years, e.g., above waterfalls or in 

desert basins. Lack of habitat to sustain 

a large population does not necessarily 

mean that a population is destined to go 

extinct (Hilderbrand and Kershner 2000, 

p. 517). Specific criteria for viable 

population size has not been developed 

for BCT. 

Small, isolated populations are at 

greater risk from stochastic events such 

as fire, floods, and drought. However, 

the widespread geographic distribution 

of BCT conservation populations in 

numerous individual populations 

mitigates the potential of future 

catastrophic natural events to affect a 

large proportion of the populations. It is 

unlikely that a sufficient number of 

populations would be lost to affect the 

overall status of the subspecies. 

Fisheries management agencies have 

the ability to maintain or reestablish 

BCT populations in areas where they are 

partially impacted or lost to natural 

catastrophic events. While not to be 

relied on for species conservation, 

restoration and reintroduction can be 

employed as tools in specific cases. For 

example, wildfire can present an 

opportunity to eliminate nonnative 

fishes that occur in BCT habitat, after 

which reestablishment of BCT can 

occur. BCT populations have been 

established in burned-over streams 

previously only occupied by nonnative 

trout, including Leeds Creek and South 

Ash Creek in the Pine Valley 

Mountains, and Birch Creek, a tributary 

to the Sevier River (Ottenbacher 2008, 

entire). 

Active programs are in place to 

restore metapopulations, where 

possible, within the historic range of 

BCT in Utah and Nevada (Donaldson 

2008, pp. 9–10; NDOW 2006, p. S–8). 

All GMUs currently have networked 

populations (metapopulations), and the 

strongest and largest networks occur in 

the Bear River and Northern Bonneville 

GMUs (May and Albeke 2005, p. 34). 

A population health evaluation was 

conducted for all BCT conservation 

populations, based on four health 

indicators: Temporal variability (based 

on stream length), population size, 

population production potential (growth 

and survival rates), and population 

connectivity (May and Albeke 2005, pp. 

44–49). The health evaluation indicated 

that 91 conservation populations (59 

percent) occur in stream reaches of less 

than 10 km (6 mi) (May and Albeke 

2005, pp. 44–49). Approximately 38 

conservation populations (25 percent) 

occupy stream reaches between 10 km 

(6 mi) and 31 km (19 mi), and 24 

populations (16 percent) occupy stream 

reaches of 32 km (20 mi) or more. 

Conservation populations include: 32 

percent with at least 2,000 adult BCT; 

25 percent with between 500 and 2,000 

adult BCT; 22 percent with between 50 

and 500 adult BCT; and 21 percent with 

fewer than 50 adult BCT. 

Most of the conservation populations 

(81 percent) were moderately healthy in 

terms of growth and survival 

(population production potential), based 

on habitat quality, presence of 

nonnative trout, disease risk, land uses, 

and recovery actions. Composite scores 

of conservation population general 

health included: 7 percent high; 39 

percent moderately high; 37 percent 

moderately low; and 17 percent low 

(May and Albeke 2005, pp. 44–49). Low 

to moderately low composite scores (54 

percent of BCT conservation 

populations) were primarily a result of 

the number of small, isolated 

populations. Even though most 

populations (66 percent) are small and 

isolated, these populations are found in 

a minority of the total BCT conservation 

population habitat; 70 percent of total 

habitat has BCT conservation 

populations that are moderately or 

strongly connected. As is explained 

below, these isolated populations have 

been incorporated into the BCT 

Conservation Team’s conservation 

strategies and allow for BCT 

conservation populations that are less 

susceptible to introgression, disease, 

and competition from nonnative fish. 

The BCT Conservation Team 

developed two conservation strategies 

for BCT conservation and management 

(May and Albeke 2005, p. iii). One 

strategy emphasizes isolated 

populations because they are less 

susceptible to introgression, disease, 

and competition from nonnative fish. In 

addition, multiple populations 

distributed throughout a watershed 

reduce risk because the simultaneous 

loss of all populations within the 

watershed is unlikely. The other 

strategy emphasizes preserving and 

restoring metapopulations to provide 

genetic exchange and allow for larger 

populations. Within the current range of 

BCT, and within each GMU, both 

isolated populations and 

metapopulations are present, providing 

for success of both conservation 

strategies. 

The best available information 

indicates that, while most BCT 

conservation populations occur in small 

stream reaches (59 percent), most have 

moderately healthy growth and survival 

rates (54 percent). In addition, 70 

percent of total habitat includes 

populations that are moderately or 

strongly connected. Therefore, we find 

that BCT conservation populations are 

adequately healthy and will remain so 

in the foreseeable future. 

Nonnative Fishes 

Introduced nonnative fish are a 

potential threat to native cutthroat 

subspecies (UDWR 2000a, pp. 1–9; May 

and Albeke 2005, pp. 21–24). We 

address this potential threat factor by 

breaking it into three components: (1) 

Management practices that included 

stocking of nonnative fish; (2) 

competition of nonnative fish with BCT; 

and (3) hybridization of BCT with 

nonnative fish. We summarize all three 

of these components together in the 

summary of Factor E because they are 

interrelated. 

Fisheries Management 

Since the late 1800s, early pioneers 

and fisheries managers have 

implemented fish stocking programs 

that introduced nonnative salmonids 

into lake and stream habitats of BCT. 

Brook trout were introduced into waters 

in Utah as early as 1875, rainbow trout 

in 1883, and brown trout (Salmo trutta) 

possibly as early as 1895 (Popov and 

Low 1950, pp. 49–57; Sigler and Miller 

1963, pp. 29–54). It is unknown exactly 

when nonnative cutthroat were 

introduced; in 1899, 11,000 adults and 

yearling cutthroat trout were sent to the 

Fish and Game Warden in Salt Lake City 

(Ravenel 1900, pp. 35–118). This 

delivery may have included several 

subspecies, including Yellowstone 

cutthroat trout (Sigler and Miller 1963, 

pp. 29–54). The earliest stocking records 

indicate large numbers of young 

nonnative fish were stocked for decades 

into accessible waters in an effort to 

restore or sustain a high-quality fishery 

(Holden et al. 1997, pp. 2–1 to 2–13). 


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In 1915, nearly 2 million cutthroat 

and more than 7 million other trout 

were planted in Utah waters alone 

within the Bonneville Basin (Cope 1955, 

pp. 89–93). Of the cutthroat stocked in 

1915, 100,000 were from Utah, and the 

remainder were collected from Bear 

Lake and other productive cutthroat 

populations and stocked into less 

productive or exploited systems. From 

1915 to 1952, more than 100 million 

cutthroat were planted, comprising 

about one-third of the total stocking 

effort in Utah; approximately 45 percent 

were imported from Utah, almost 

exclusively from Yellowstone Lake 

(Cope 1955, pp. 89–93, as reported from 

biennial Utah State Fish and Game 

Commission reports 1915–1952). 

Comprehensive stocking records from 

the turn of the century for the 

Bonneville Basin in Nevada, Idaho, and 

Wyoming are not readily available 

because most of these peripheral areas 

of the Bonneville Basin are remote and 

inaccessible. However, it has been 

suggested that settlers moved fish 

among drainages in remote areas like 

the Snake Valley and the Pine Valley 

Mountains in the mid-to late-1800s 

(Miller and Alcorn 1946, pp. 173 193; 

Popov and Low 1950, pp. 38–39; 

Behnke 1992, pp. 134–135). Fish 

transplanting among and across 

drainages, without oversight, consent, or 

record-keeping, was likely common in 

remote pioneer settlements. 

Although many nonnative species 

were once stocked throughout Utah, 

salmonid species, particularly rainbow 

trout, Yellowstone cutthroat trout, and 

brook trout, comprise the greatest 

potential threat to BCT. Rainbow and 

Yellowstone cutthroat trout can 

interbreed with BCT (Busack and Gall 

1981, pp. 948–950; Weigel et al. 2002, 

pp. 397–401), and brook trout can be a 

competitor for food sources (Peterson et 

al. 2004, p. 769) (see next section on 

Competition). Rainbow trout were 

regularly stocked into most cold, clearwater stream systems and 

impoundments throughout the 

Bonneville Basin (Duff 1988, pp. 121–

127; Holden et al. 1997, pp. 2–5 to 2–

13). Rainbow trout were commonly 

stocked at accessible sites, which was 

not always successful in establishing 

wild populations (those that naturally 

reproduce and recruit in the wild). As 

a result, annual stocking was necessary 

to maintain a sustainable fishery. Heavy 

annual stocking has taken place in some 

streams for more than a century. In the 

past 30 years, stocking was modified to 

prevent introduction of nonnative 

salmonids into waters with known pure 

populations of BCT in Utah (Holden et 

al. 1997, pp. 2–13 to 2–22). 

Because of the nearby source of fry in 

Yellowstone Lake, Yellowstone 

cutthroat trout were readily available for 

stocking. Yellowstone and other 

subspecies of cutthroat trout were 

stocked into streams to supplement the 

declining native fishery. In some cases, 

(e.g., Bear Lake) substantial records exist 

of annual stocking of Yellowstone 

cutthroat trout and other species. 

Despite this stocking, Yellowstone 

cutthroat trout did not necessarily 

become established in all waters into 

which they were stocked, and BCT in 

some areas have resisted hybridization 

with and replacement by nonnative 

trout (e.g., Bear Lake) (Behnke 1992, p 

137). Genetic information is not 

currently sufficient to clearly discern 

Yellowstone cutthroat trout from BCT in 

the Bear River drainage because of their 

recent evolutionary divergence; 

however, morphological characteristics 

are distinctive between BCT and 

Yellowstone cutthroat trout and can be 

used to determine hybridization where 

it is suspected (Behnke 1992, pp. 132–

138; Shiozawa 2008, p. 1). 

State fish and wildlife agencies no 

longer stock nonnative trout in BCT 

habitat, and are implementing strategies 

to minimize impacts to BCT from 

nonnatives, such as installing fish 

barriers, removing nonnative fish, and 

increasing nonnative fish bag limits. 

Competition From Nonnative Fish 

Nonnative trout are known to 

compete with BCT (Behnke 1992, p. 54). 

Brown trout can successfully compete 

with BCT (Budy et al. 2005, pp. xi–xiii), 

and brook trout can displace cutthroat 

trout when they occur in the same 

habitat (Peterson et al. 2004, p. 769). 

Nonnative fish are sympatric with BCT 

within currently occupied habitat in the 

four GMUs (May and Albeke 2005, pp. 

27–28). Currently occupied BCT habitat 

includes 37 percent (1,365 km/848 mi) 

without nonnative fish, and 63 percent 

(2,466 km/1,532 mi) with nonnative 

fish. The majority of habitat with 

nonnative fish is in the Bear River 

(1,398 km/869 mi) and Northern 

Bonneville (1,024 km/636 mi) GMUs. 

Only 45 km (28 mi) in the Southern 

Bonneville GMU have nonnative fish. 

No nonnative fish exist within the West 

Desert GMU in BCT conservation 

population habitat. 

BCT conservation populations 

represent approximately 87 percent of 

currently occupied habitat (the other 13 

percent includes sport fish) (May and 

Albeke 2005, p. 31). Of the 153 BCT 

conservation populations, 97 (63 

percent) have no interaction with 

nonnative fish, and 56 (37 percent) are 

sympatric with nonnative fish (May and 

Albeke 2005, p. 31). 

Natural and human-made barriers 

protect some BCT populations from 

competition with nonnative fish. 

Rangewide, barriers assist in protecting 

35 BCT conservation populations 

occupying 480 km (298 mi) of stream 

(Burnett 2008b, pp. 1– Barriers help 

protect populations from nonnative fish 

invasion, but negative effects, such as 

blocking fish movement and 

fragmenting habitat, should be assessed 

and balanced before installing barriers. 

Therefore, this strategy for managing 

nonnative fish is not appropriate for all 

native cutthroat populations. 

Hybridization With Nonnative Fishes 

The scientific criteria for describing 

and formally recognizing taxonomic 

species of fish are based almost entirely 

on morphological characters (Behnke 

1992, pp. 7–11). The advent of 

molecular genetic techniques in the 

mid-1960s added an additional set of 

biological markers that are used to 

distinguish species and subspecies of 

native trout in the western United 

States. Most genetic analyses on native 

cutthroat trout have confirmed the 

evolutionary distinctness among species 

and subspecies that had been described 

taxonomically on the basis of 

morphology (Behnke 1992, pp. 7–11). 

Cutthroat trout populations that are 

less than 10 percent introgressed with 

nonnative species (or other cutthroat 

subspecies) retain morphological, 

behavioral, and ecological 

characteristics of their nonintrogressed 

ancestors (UDWR 2000a, pp. 1–9). 

Individuals of a particular cutthroat 

trout subspecies can possess nuclear 

genes from another taxon, detectable 

only by molecular genetic techniques, 

while still conforming morphologically, 

behaviorally, and ecologically to the 

scientific taxonomic description of the 

parental native species (Busack and Gall 

1981, pp. 948–950; Weigel et al. 2002, 

pp. 397–401). 

We do not consider populations or 

individual fish conforming 

morphologically to the scientific 

taxonomic description of BCT to be a 

hybridization threat to BCT. Although 

such individuals may have a low 

frequency of genes from another taxon 

(less than 10 percent), we have found no 

information indicating that such 

individuals express behavioral, 

ecological, or life-history characteristics 

differently than BCT native to a 

particular geographic area. The 

frequency of genes from other taxons 

will likely remain low in BCT 

populations for several reasons: (1) In 


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some locations BCT likely can have an 

ecological advantage over nonnative fish 

because they have adapted over long 

time periods to their specific habitat; (2) 

stocking of nonnative trout in BCT 

habitat is no longer practiced by fish 

and wildlife agencies; and (3) 61 percent 

of BCT conservation populations are 

isolated by human-caused or natural 

barriers, protecting them from 

increasing numbers of nonnative trout 

(May and Albeke 2005, p. 37). 

Some introgressed populations may 

be valuable to the overall conservation 

and survival of a species or subspecies 

(Campton and Kaeding 2005, pp. 1323–

1324; USFWS 2003, pp. 46992–46993), 

because they can still express important 

behavioral, life history, or ecological 

adaptations of the indigenous 

population within a particular 

geographic area. BCT have evolved in 

varying environmental conditions in 

differing habitats across its range, and 

these conditions have likely influenced 

its behavioral and life history traits. For 

example, BCT with fluvial and adfluvial 

life-history strategies migrate up small 

streams to spawn, and BCT with a 

resident life-history strategy are able to 

conduct their entire life history 

(spawning, nursery/rearing, adult stage 

including overwintering) in headwater 

tributaries that provide all necessary 

life-history habitat types. Environmental 

conditions particular to a specific BCT 

population’s ecological setting (e.g., 

latitude, elevation, temperature and 

precipitation regime) may allow for 

development of locally adapted traits 

that would justify preservation of a 

partially introgressed population. 

Maintaining unique life-history traits 

can outweigh the negative aspects of 

limited introgression. Thus, agencies 

should carefully evaluate the long-term 

conservation implications of strategies 

for managing introgressed BCT 

populations within the range of the BCT 

(USFWS 2003, pp. 46992–46993; 

Campton and Kaeding 2005, pp. 1323–

1324), as different strategies may be 

appropriate for different populations. 

No standards exist that define exact 

thresholds for acceptable levels of 

hybridization in cutthroat trout; 

however, we assessed all relevant 

scientific and commercial information 

available in order to arrive at generally 

applicable standards. These standards 

are applicable to other species of 

cutthroat trout we have assessed, 

including the Yellowstone (71 FR 8818, 

February 21, 2006) and Colorado River 

(72 FR 32589, June 13, 2007) cutthroat 

trout subspecies. Similar standards were 

applied to the Westslope cutthroat trout 

(WCT) (68 FR 46989, August 7, 2003); 

however, specific research was 

conducted indicating that WCT 20- 

percent introgressed with rainbow trout 

were indistinguishable morphologically 

from nonintrogressed WCT (Weigel et 

al. 2002, pp.397–401). Species-specific 

research comparing morphological 

characteristics to genetic introgression 

thresholds has not been conducted on 

other cutthroat subspecies; therefore, we 

used the more conservative threshold of 

10 percent to define BCT conservation 

populations. 

When BCT are sympatric with 

rainbow trout and nonnative subspecies 

of cutthroat trout, introgressed 

populations can occur, and because of 

this, researchers have studied the 

genetic status of BCT. These studies 

have measured levels of introgression in 

the BCT in targeted areas of its range, 

but have not, additionally, measured the 

morphological characteristics present at 

varying levels of introgression. The 

rangewide status report includes a 

summary of BCT genetic status (May 

and Albeke 2005, pp. 21–24). 

Genetic testing was conducted in 

more than 784 km (487 mi) of BCT 

occupied habitats (20 percent of 

occupied habitat) (May and Albeke 

2005, pp. 21–24). This research was 

conducted specifically in populations 

that appeared to be typical of the BCT 

phenotype; while results help elucidate 

the level of introgression in BCT, they 

cannot be used to summarize rangewide 

introgression levels. Test results showed 

no evidence of introgression in samples 

from 611 km (411 mi) of occupied 

habitat (17 percent of occupied habitat). 

An additional 1,215 km (755 mi) of 

occupied habitat (32 percent of 

occupied habitat) has populations 

suspected to be genetically unaltered, 

based on the absence of introduced 

hybridizing species and of stocking 

records for hybridizing species. The 

BCT Coordination Team has classified 

these as conservation populations. 

Hybridized fish occur in approximately 

122 km (76 mi) of stream habitat 

(4 percent of occupied habitat). An 

additional 1,831 km (1,138 mi) of 

habitat (48 percent of occupied habitat) 

contains fish that are potentially 

hybridized, based on the presence of 

nonnative hybridizing species or 

records indicating past stocking of 

nonnative hybridizing species. 

Researchers also assessed the genetic 

contamination risk, based on proximity 

and accessibility of rainbow trout and 

nonnative cutthroat trout, for the 153 

BCT conservation populations (May and 

Albeke 2005, p. 37). A low genetic risk 

was found in BCT populations (94 

populations; 61 percent) where a barrier 

provides complete blockage to upstream 

fish movement of introduced 

hybridizing species. A moderately low 

genetic risk was found in BCT 

populations greater than 10 km (6 mi) 

from hybridizing species or subspecies, 

and a moderately high risk was found in 

BCT populations within 10 km (6 mi) of 

hybridizing species or subspecies (27 

populations; 18 percent). A high risk 

rating was found in BCT populations 

(32 populations; 21 percent) sympatric 

with hybridizing species in the same 

stream segment. Of the populations that 

were rated with low risk of genetic 

contamination, 87 (93 percent) were 

identified as being isolated populations. 

Summary of Nonnative Fishes 

Despite the presence of nonnative fish 

species sympatric with BCT, we find 

that stocking, competition, and 

hybridization do not pose significant 

threats to BCT, because: (1) In some 

locations BCT likely can have an 

ecological advantage over nonnative fish 

because they have adapted over long 

time periods to their habitat; (2) welldistributed core populations of BCT 

persist in streams with nonnative fish; 

(3) 61 percent of BCT populations are 

isolated from nonnative fish by natural 

or constructed barriers; and (4) stocking 

of nonnative fish no longer occurs in 

waters with BCT conservation 

populations. In addition, programs are 

being implemented to remove nonnative 

trout, through mechanical or chemical 

means, from BCT waters in all four 

States (NDOW 2006, p. S–22; IDFG 

2008, pp. 9–10; Donaldson 2008, p. 5; 

WGFD 2008, p. 10). In Utah, between 

2001 and 2007, nonnative fish removal 

was conducted on more than 80 km 

(50 mi) of BCT streams (Donaldson 

2008, p. 5). 

Groundwater Pumping 

Multiple filings for groundwater 

withdrawal from both the carbonaterock and alluvial aquifers in the Great 

Basin are currently in place within the 

historic range of BCT populations in the 

West Desert GMU. Southern Nevada 

Water Authority (SNWA) has applied to 

the BLM for issuance of rights-of-way to 

construct and operate a system of 

regional water supply and conveyance 

facilities. The project would include 

conveyance of up to 24,384 hectares per 

meter (ha-m) (200,000 acre-feet per year 

(ac-ft)) of groundwater—20,360 ha-m 

(167,000 ac-ft) by SNWA with the 

remaining capacity provided for Lincoln 

County Water District from six 

hydrographic basins (SNWA 2007, p. 1–

1). The groundwater that SNWA intends 

to convey would be from both existing 

and future permitted water rights in 

hydrographic basins of the Great Salt 

Lake Desert Regional Flow System 


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(Nevada and Utah) and White River 

Flow System (Nevada). 

SNWA’s Groundwater Development 

(GWD) Project includes construction 

and operation of groundwater 

production wells, water conveyance 

facilities, and power facilities. The 

proposed production wells and facilities 

would be located on public lands 

managed by BLM in Nevada. No 

facilities are planned in Utah (SNWA 

2007, p. 1–1). 

The Nevada State Engineer issued a 

ruling on April 16, 2007, approving a 

major portion of the SNWA 

groundwater rights applications for the 

Spring Valley hydrographic basin. 

SNWA can pump 4,877 ha-m (40,000 

ac-ft) annually from the basin, with the 

potential for an additional 2,438 ha-m 

(20,000 ac-ft) based on results of 10 

years of monitoring that will be 

conducted for the initial pumping 

allocation (NSE 2007, p. 56). The 

Nevada State Engineer hearings on 

SNWA water rights applications in 

Snake Valley are projected for fall 2009. 

In addition to the water awarded to 

SNWA in Spring Valley, filings for 6251 

ha-m (50,680 ac-ft) in Snake Valley are 

pending. 

New, large-volume filings in the State 

of Utah include: Millville Irrigation 

Co.—15172 ha-m (123,000 ac-ft) in Wah 

Wah Valley; the Confederate Tribes of 

the Goshute Reservation—6168 ha-m 

(50,000 ac-ft) in Deep Creek Valley; 

Central Iron County Water Conservancy 

District—4564 ha-m (37,000 ac-ft) in 

Hamlin, Pine, and Wah Wah Valleys; 

private parties in Snake Valley—1294 

ha-m (10,490 ac-ft); and the State of 

Utah School and Institutional Trust 

Lands—1105 ha-m (8960 ac-ft) in Snake 

Valley (UGS 2008, entire). We did not 

receive information detailing future 

plans for development on the filings of 

these Utah water rights. 

The SNWA GWD Project is 

anticipated to be completed and may 

begin pumping in January 2014 (SNWA 

2007, pp. 4–11). Prior to its completion, 

baseline data collection and research on 

biologic and hydrologic impacts will be 

completed and an intensive monitoring 

program will be put in place to monitor 

and mitigate for Project effects. At the 

present time, SNWA anticipates that 

ultimately between 110 and 200 

groundwater production wells may be 

required for the GWD Project. However, 

the specific locations of these wells are 

dependent upon future rulings from the 

Nevada State Engineer, exploratory 

drilling results, agency agreements, and 

results of actual groundwater pumping. 

SNWA anticipates that it may take up to 

20 years or more to site and install all 

of the groundwater production wells for 

the project (SNWA 2007, p. 2–1). 

A great deal of uncertainty exists 

regarding the long-term effects of the 

groundwater pumping for aquifers and 

surface waters in the Great Basin. 

However, well locations will generally 

be sited in valley bottoms and be 

withdrawing water from deep carbonate 

and alluvial aquifers. BCT populations 

are generally located in headwater 

streams in the West Desert GMU, and it 

is anticipated that direct effects to BCT 

populations and their habitat will be 

minimal or nonexistent. Additionally, 

SNWA entered into a stipulation with 

the Department of the Interior regarding 

SNWA’s GWD Project water 

withdrawals in the Spring Valley 

hydrographic basin. The goals of this 

stipulation include avoidance of any 

effects to water-dependent ecosystems 

within the boundaries of Great Basin 

National Park and avoidance of 

unreasonable adverse impacts to waterdependent ecosystems in the remainder 

of the project area. This will be 

accomplished through hydrologic and 

biologic monitoring, management, and 

mitigation plans designed to identify, 

avoid, and mitigate effects of 

groundwater withdrawal on dependent 

ecosystems (SNWA 2008, p. 15). 

It has been hypothesized that water 

development in two areas of the GWD 

Project, the Spring Valley and Snake 

Valley Basins, could have indirect 

effects to BCT habitats in the West 

Desert GMU. Groundwater pumping 

could result in the lowering of valley 

water tables and spring discharge rates 

and result in drying and desiccation of 

wetland and riparian phreatophytic 

(deep rooted) vegetation. This could 

likely result in an increase in fire 

frequency in Great Basin valley floors 

that are adjacent to drainages that have 

BCT populations in headwater streams. 

Riparian vegetation in drainages of the 

Snake and Deep Creek ranges where 

BCT occur could become more 

susceptible to these fires. However, 

there is a great deal of uncertainty as to 

whether this scenario will occur or if it 

will have impacts to BCT as no 

information exists regarding what the 

actual effects of pumping would be to 

valley vegetation or fire frequency. At 

this time, we know of no information 

that indicates to us that groundwater 

pumping in the West Desert GMU is 

significantly affecting BCT now or into 

the foreseeable future. 

Summary of Factor E 

Despite the potential for increased 

risk to BCT populations resulting from 

future climate change, we found no 

scientific and commercial information 

leading us to conclude that climate 

change is currently a significant threat 

to BCT conservation populations, or 

will become so within the foreseeable 

future. 

We assessed the potential risks to BCT 

conservation populations associated 

with fragmentation and isolation of 

small BCT conservation populations, 

including stochastic, catastrophic, 

natural events, and find that they do not 

now, nor will in the foreseeable future, 

significantly threaten the status of BCT 

to the extent that listing under the Act 

as a threatened or endangered species is 

warranted. 

We assessed the potential threats 

posed by nonnative species, including 

historical stocking, competition, and 

introgressive hybridization with 

rainbow trout or other cutthroat 

subspecies. Nonnative fish species exist 

in 63 percent of occupied BCT habitat. 

However, 61 percent of BCT 

populations are isolated from nonnative 

fish by natural or constructed barriers, 

and stocking of nonnative fish no longer 

occurs in BCT waters. These factors, 

combined with the current distribution 

of conservation populations, indicate 

that nonnatives do not currently affect 

the status of BCT to the extent that 

listing under the Act as a threatened or 

endangered species is warranted. In 

addition, management practices focused 

on removing and preventing 

introduction of nonnative fish within 

BCT habitat, provide reasonable 

assurance that this potential threat 

factor will not increase within the 

foreseeable future. 

Foreseeable Future 

In the context of the Act, the term 

‘‘threatened species’’ means any species 

(or subspecies or, for vertebrates, 

distinct population segments) 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 Act does not 

define the term foreseeable future; 

however, we consider it to be affected 

by the biological and demographic 

characteristics of the species, as well as 

our ability to predict or extrapolate the 

effects of threats facing the species in 

the future. Quantification of the time 

period corresponding to the foreseeable 

future is challenging because it 

necessitates making predictions about 

inherently dynamic political, legal, and 

social mechanisms that influence the 

degree and immediacy of potential 

threats to the species. 


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For the purpose of this finding, the 

‘‘foreseeable future’’ is the period of 

time over which events or effects 

reasonably can or should be anticipated, 

or trends reasonably extrapolated, such 

that reliable predictions can be made 

concerning the status of the species in 

the future. Although we have found 

some threats to BCT are ongoing at low 

levels and that various localized areas 

may be affected by specific problem 

activities, as discussed in the Summary 

of Factors section, we did not find any 

information to suggest that threats will 

rise to levels that would significantly 

threaten BCT rangewide to the extent 

that the species would warrant listing 

under the Act. 

Although we did not find any 

information to allow us to reliably 

predict that threats would increase 

significantly in the future, predicting 

and managing for the effects of potential 

future threats will be facilitated by the 

BCT conservation plans that are in place 

at the State and rangewide level (see 

Conservation Actions section under 

Factor D). Monitoring of BCT 

population numbers and habitat 

conditions is included in the State and 

rangewide conservation plans and any 

significant decreases in BCT 

populations or habitat conditions 

should be identified and effectively 

mitigated by using the methods 

developed in these conservation plans. 

State and Federal agency participation 

in BCT conservation plans is voluntary; 

however, State plans are typically in 

place indefinitely, or have a term of 

agreement for 5–10 years with renewal 

provisions for a similar time period. The 

rangewide BCT conservation agreement 

was renewed in 2008 for 10 years with 

the commitment that it would be 

extended for an additional 10 years 

upon expiration. In addition, the States 

within the range of the BCT have an 

established record of managing for the 

species (see Factor D). We find that the 

BCT conservation plans will be in place 

and operating for at least 20 years. We 

consider the status of the BCT to be 

reasonably predictable with established 

management practices in place because 

many of the threats to the species are 

effectively mitigated by these practices; 

outside the timeframe of the 

conservation plans, we are unable to 

make reliable predictions regarding the 

threats to the species and the effect of 

those threats on the status of the 

species. Therefore, the foreseeable 

future for BCT is 20 years with respect 

to most threats. 

Our ability to predict the effects of 

future threats is limited to our 

knowledge of the timeframe of the 

threats potentially facing the BCT, and 

the conservation activities taking place 

to address them. We assessed activities 

that could potentially affect BCT 

populations under the Summary of 

Factors section. Livestock grazing was a 

concern in the early 1900’s, but recent 

management practices appear to have 

reduced effects to watersheds, and these 

practices are expected to continue for at 

least 20 years. Road construction or 

maintenance, timber harvest, and water 

diversions and depletions are expected 

to be managed consistently within at 

least the next 20 years, and are not 

expected to result in a downward trend 

in BCT population status. The 

foreseeable future for oil and gas 

development is possibly shorter than for 

other threats (i.e., less than 20 years), 

because this threat is not specifically 

mitigated by conservation actions 

identified in the State conservation 

plans; however, oil and gas 

developments are mostly outside the 

historic range of the BCT, and are not 

creating a downward trend in 

population status. Recreational angling 

is currently regulated, and no 

downward trend in population status 

exists due to this activity. Disease in 

BCT is being mitigated through 

conservation actions that are expected 

to continue for at least the next 20 years. 

Factors related to the presence of 

nonnative fish species, such as 

predation, competition, and genetic 

introgression, are being mitigated 

through conservation actions that are 

expected to continue for at least the next 

20 years. 

Climate change projections are 

considered fairly robust for the current 

century on a continental scale, but, as 

discussed above, we cannot yet make 

reliable predictions as to the magnitude 

or timing of likely temperature increases 

within the range of the BCT. Therefore, 

for the purposes of analyzing the threat 

of climate change to the BCT, the future 

is only foreseeable to the extent of our 

determination that some additional 

temperature increase is likely. We 

cannot determine that the BCT will 

become endangered due to an 

unquantifiable amount of temperature 

increase, particularly given the BCT’s 

apparent adaptability to a relatively 

broad spectrum of habitat conditions, 

although we recognize that it is possible 

that climate change will eventually have 

more significant impacts. 

We have determined that the 

immediacy and magnitude of the abovementioned threats will not significantly 

degrade the 80 percent of BCT habitat 

that is currently in fair to excellent 

condition within the next 20 years, in 

part due to regulatory mechanisms and 

management practices (no nonnative 

stocking, combined with nonnative 

removal programs) that have been 

implemented and shown to be effective 

by State and Federal management 

agencies, and that we have reasonable 

assurance will continue for at least the 

next 20 years. 

Significant Portion of the Range 

As required by the Act, we considered 

the five potential threat factors to assess 

whether the BCT is threatened or 

endangered throughout all or a 

significant portion of its range. When 

considering the listing status of a 

species, the first step in the analysis is 

to determine whether the species is in 

danger of extinction throughout all of its 

range. If this is the case, then we list the 

species in its entirety. For instance, if 

the threats to a species are directly 

acting on only a portion of its range, but 

they are at such a large scale that they 

place the entire species in danger of 

extinction, we would list the entire 

species. 

Based on the best available scientific 

and commercial information available 

addressing BCT distribution and 

potential threats, especially the 

rangewide status report for BCT (May 

and Albeke 2005, entire), we find that 

the BCT is not likely to become 

endangered in the foreseeable future 

throughout all of its range. 

On March 16, 2007, a formal opinion 

was issued by the Solicitor of the 

Department of the Interior, ‘‘The 

Meaning of ‘In Danger of Extinction 

Throughout All or a Significant Portion 

of Its Range’ ’’ (DOI 2007). A portion of 

a species’ range is significant if it is part 

of the current range of the species and 

is important to the conservation of the 

species because it contributes 

meaningfully to the representation, 

resiliency, or redundancy of the species. 

The contribution must be at a level such 

that its loss would result in a decrease 

in the ability to conserve the species. 

We evaluated the BCT throughout its 

current range to determine if any 

portion is likely to become threatened or 

endangered within the foreseeable 

future, and if so, whether that portion is 

important to the conservation of the 

species because it contributes 

meaningfully to the resiliency, 

representation, or redundancy of the 

species. 

The range of a species can 

theoretically be divided into portions in 

an infinite number of ways. However, 

there is no purpose in analyzing 

portions of the range that are not 

reasonably likely to be significant and 

threatened or endangered. To identify 

portions that warrant further 

consideration, we determine whether 


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there is substantial information 

indicating that (i) the portions may be 

significant and (ii) the species may be in 

danger of extinction there or likely to 

become so within the foreseeable future. 

In practice, a key part of this analysis is 

whether the threats are geographically 

concentrated in some way. If the threats 

to the species are essentially uniform 

throughout its range, no portion is likely 

to warrant further consideration. 

Moreover, if any concentration of 

threats applies only to portions of the 

range that are unimportant to the 

conservation of the species, such 

portions will not warrant further 

consideration. 

If we identify portions of the range 

that warrant further consideration, we 

determine whether the species is 

threatened or endangered in any 

significant portion of its range. 

Depending on the biology of the species, 

its range, and the threats it faces, it may 

be more efficient to address the 

significance question first, or the status 

question first. If we determine that a 

portion of the range is not significant, 

we need not determine whether the 

species is threatened or endangered 

there; similarly, if we determine that the 

species is not threatened or endangered 

in a portion of its range, we need not 

conduct significance analysis. 

The concepts of ‘‘resiliency,’’

redundancy,’’ and ‘‘representation’’ are 

indicators of the conservation value of 

portions of the range. Resiliency of a 

species allows the species to recover 

from periodic disturbance. A species 

will likely be more resilient if large 

populations exist in high-quality habitat 

that is distributed throughout the range 

of the species in such a way as to 

capture the environmental variability 

found within the range of the species. It 

is likely that the larger size of a 

population will help contribute to the 

viability of the species overall. 

Therefore, a portion of the range of a 

species may make a meaningful 

contribution to the resiliency of the 

species if the area is relatively large and 

contains particularly high-quality 

habitat or if its location or 

characteristics make it less susceptible 

to certain threats than other portions of 

the range. 

Redundancy of populations may be 

needed to provide a margin of safety for 

the species to withstand catastrophic 

events. This does not mean that any 

portion that provides redundancy is a 

significant portion of the range of a 

species. The idea is to conserve enough 

areas of the range such that random 

perturbations in the system act on only 

a few populations. Therefore, each area 

must be examined based on whether 

that area provides an increment of 

redundancy that is important to the 

conservation of the species. 

Adequate representation insures that 

the species’ adaptive capabilities are 

conserved. Specifically, the portion 

should be evaluated to see how it 

contributes to the genetic diversity of 

the species. The loss of genetically 

based diversity may substantially 

reduce the ability of the species to 

respond and adapt to future 

environmental changes. A peripheral 

population may contribute meaningfully 

to representation if there is evidence 

that it provides genetic diversity due to 

its location on the margin of the species’

habitat requirements. 

We assessed threats at the watershedbased GMU level, because standardized 

fish monitoring methods and BCT 

management methods are watershed 

based. The four GMUs are 

geographically and hydrologically 

distinct; they also delineate BCT 

populations in logical biogeographical 

and taxonomic subgroups. Based on the 

best available scientific and commercial 

information regarding the abundance of 

BCT, and our assessment of threats to 

the species, throughout its current 

range, we find that no individual GMU 

is likely to become threatened or 

endangered in the foreseeable future 

because threats are evenly distributed 

throughout the range of the species. 

Further subdividing of BCT 

populations or habitat into smaller 

portions than GMUs would require 

unscientific methodology. In addition, 

smaller subdivisions of populations 

would not, individually, be significant 

to the subspecies. We find that areas 

smaller than the GMU would not 

meaningfully contribute to the 

resilience, redundancy, or 

representation of the BCT. Losses of 

habitat or species from areas smaller 

than the GMU level would not threaten 

the entire GMU, and a sufficient number 

of GMUs exist to ensure species 

redundancy and resiliency. No 

significant ecological differences exist at 

levels smaller than the GMUs to affect 

representation of the subspecies. 

Threats are similar in all four GMUs, 

and no individual GMU has threats of 

a magnitude that the subspecies is 

threatened or endangered within it. 

Therefore, we have determined that no 

significant portion of the BCT range is 

in danger of extinction or likely to 

become so within the foreseeable future. 

Distinct Vertebrate Population Segment 

(DPS) 

Pursuant to section 4(a)(1) of the Act, 

we must determine whether any species 

is an endangered species or a threatened 

species because of any of the threat 

factors identified therein. Section 3(15) 

of the Act defines ‘‘species’’ to include 

‘‘any species or subspecies of fish and 

wildlife or plants, and any distinct 

vertebrate population segment of fish or 

wildlife that interbreeds when mature’’

(16 U.S.C. 1532 (16)). To interpret and 

implement the distinct vertebrate 

population portion of the definition of 

a species under the Act and 

congressional guidance, the Service and 

the National Marine Fisheries Service 

(now the National Oceanic and 

Atmospheric Administration—

Fisheries) published, on February 7, 

1996, an interagency Policy Regarding 

the Recognition of Distinct Vertebrate 

Population Segments under the Act 

(DPS Policy; 61 FR 4722). The policy 

allows for more refined application of 

the Act that better reflects the 

conservation needs of the taxon being 

considered, and avoids the inclusion of 

entities that may not warrant protection 

under the Act. 

Under our DPS policy, three elements 

are considered in a decision regarding 

the status of a possible DPS as 

endangered or threatened under the Act. 

These are applied similarly for 

additions to the List of Endangered and 

Threatened Wildlife and Plants, 

reclassification, and removal from the 

List. They are: (1) Discreteness of the 

population segment in relation to the 

remainder of the taxon; (2) the 

significance of the population segment 

to the taxon to which it belongs; and (3) 

the population segment’s conservation 

status in relation to the Act’s standards 

for listing (i.e., whether the population 

segment is, when treated as if it were a 

species, endangered or threatened). 

Discreteness refers to the isolation of a 

population from other members of the 

species and we evaluate this based on 

specific criteria. If a population segment 

is considered discrete, we must consider 

whether the discrete segment is 

‘‘significant’’ to the taxon to which it 

belongs by using the best available 

scientific information. If we determine 

that a population segment is discrete 

and significant, we then evaluate it for 

endangered or threatened status based 

on the Act’s standards. 

We assessed threats at the watershedbased GMU level, because standardized 

fish monitoring methods and BCT 

management methods are watershed 

based. The four GMUs are 

geographically and hydrologically 

distinct; they also delineate BCT 

populations in logical biogeographical 

and taxonomic subgroups. In addition, 

each GMU is significant to the 

continued existence of the species. 

However, based on the best available 


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scientific and commercial information 

regarding the abundance of BCT, and 

our assessment of threats to the species, 

throughout its current range, we find 

that no individual GMU is likely to 

become threatened or endangered in the 

foreseeable future because threats are 

evenly distributed throughout the range 

of the species. 

The four GMUs meet the first two 

criteria in the DPS policy, but the 

conservation status of each is stable. 

Further subdividing of BCT populations 

or habitat into smaller portions than 

GMUs would require unscientific 

methodology. In addition, while it is 

possible that smaller units would meet 

the discreteness criteria in the DPS 

policy, it is unlikely that any smaller 

area would be significant to the 

subspecies. 

Finding 

This status review includes 

substantial information that was not 

available at the time of the 2001 status 

review and 12-month finding (66 FR 

51362), in particular, the information 

obtained from May and Albeke (2005). 

We requested a peer review of May and 

Albeke (2005); peer reviews were 

conducted by five recognized cutthroat 

trout experts who found that the 

document provided sound scientific 

data on the rangewide status of BCT. 

Populations of BCT have been greatly 

reduced over the last 200 years, with 

much loss occurring in the late 19th and 

early 20th century (Behnke 1992, pp. 

132–138). However, recent surveys have 

shown that the numbers of BCT 

populations have increased in the last 3 

decades and the subspecies remains 

widely distributed throughout a large 

geographic area. We attribute the 

historic decline in the distribution of 

BCT to the introduction of nonnative 

sport fish into BCT habitat that began in 

the late 1800s. The wide distribution of 

rainbow trout and nonnative cutthroat 

trout caused problems through 

competition, hybridization, and 

predation. In some places, introduced 

fish expanded and colonized new 

habitat, and formed naturally 

reproducing populations that occupy 

the former, and in some cases current, 

range of BCT. 

We found no evidence of continuing 

declines in the overall distribution or 

abundance of BCT during the last 

several decades. A substantial increase 

in the number of known populations 

has been documented (May and Albeke 

2005, pp. 63–64), and habitat quality is 

good to excellent in over half (52 

percent) of BCT habitat, and fair to 

excellent in 80 percent of BCT habitat. 

Management agencies have focused on 

the protection and restoration of 

conservation populations of BCT in all 

currently occupied watersheds. 

Additional focus is on habitat 

restoration activities and fisheries 

management actions designed to benefit 

BCT. Some recognized threats to BCT, 

such as excessive harvest by anglers and 

stocking of nonnative fishes, are now 

regulated or discontinued so that they 

no longer threaten the continued 

existence of BCT. Conservation actions 

have resulted in improved population 

levels in some areas (Ottenbacher 2008, 

entire). 

At least 153 BCT conservation 

populations collectively occupy about 

3,316 km (2,061 mi) of stream habitat in 

22 watersheds (HUCs) in Utah, Idaho, 

Nevada, and Wyoming. These 

populations qualify as conservation 

populations of BCT under standards 

developed by the States that are 

consistent with our assessment of best 

available science. Conservation 

populations are distributed throughout 

the four GMUs within the historic range 

of the BCT. Of the 153 conservation 

populations identified by May and 

Albeke (2005, p. 31), about 71 (46 

percent) are core populations comprised 

of nonintrogressed BCT (greater than 99 

percent genetic purity). 

Hybridization, mostly with nonnative 

rainbow trout and nonnative subspecies 

of cutthroat trout that have established 

self-sustaining populations in many 

areas in the range of BCT, has 

historically been an issue of 

management concern. However, current 

State management has greatly reduced 

opportunities for further genetic 

introgression. States continue to 

monitor introgression in BCT 

throughout its range. We find that the 

limited presence of genetic material 

from other fish species or subspecies 

(typically less than 10 percent) is not a 

threat to BCT conservation populations. 

Populations or individual fish with a 

low level of introgression are 

morphologically, ecologically, and 

behaviorally indistinguishable from 

nonintrogressed (i.e., pure) BCT. 

Slightly introgressed BCT populations, 

with low amounts of genetic 

introgression detectable only by 

molecular genetic methods (i.e., 

conservation populations), are an 

important component of BCT 

conservation. Genetically pure 

populations (71 core populations) are 

distributed throughout the current range 

of BCT. State and Federal agencies are 

implementing strategies and actions to 

protect BCT populations from invasion 

of nonnative species or subspecies that 

may interbreed with BCT. 

Brook trout, brown trout, and rainbow 

trout compete with BCT where they are 

sympatric. Managers are monitoring 

competition from nonnative fish in BCT 

waters, and implementing ongoing 

management strategies and actions to 

curtail it. However, 1,365 km (848 mi) 

of habitat occupied by BCT conservation 

populations are free of nonnative trout. 

The BCT persists as a widely 

distributed subspecies; 153 conservation 

populations exist throughout the 

historic range, and a metapopulation 

structure exists in each GMU. 

Nonintrogressed BCT core populations 

exist in habitats secure from nonnative 

trout and thus are protected from 

potential hybridization throughout the 

subspecies’ historic range. Although 

distribution of BCT has been reduced 

from historic levels (the subspecies now 

occupies about 35 percent of historic 

habitat), the 2005 rangewide status 

report on BCT documented the 

continued existence of conservation 

populations throughout its current 

range, and that 80 percent of occupied 

habitat is in fair to excellent condition. 

We have thoroughly assessed the 

current status of BCT, the mitigation of 

existing threats, and the existence of 

laws and regulations that minimize 

adverse effects of land management and 

other activities on BCT. We find that the 

magnitude and imminence of threats do 

not indicate that the subspecies is in 

danger of extinction, or likely to become 

endangered, throughout all or any 

significant portion of its range, within 

the foreseeable future. Therefore, we 

find that listing the BCT as a threatened 

or an endangered species under the Act 

is not warranted at this time. 

References Cited 

A complete list of all references cited 

herein is available upon request from 

the Utah Ecological Services Field 

Office (see ADDRESSES section). 

Author 

The primary author of this document 

is the staff of the U.S. Fish and Wildlife 

Service, Utah Ecological Services Field 

Office (see ADDRESSES section). 

Authority: The authority for this action is 

the Endangered Species Act of 1973, as 

amended (16 U.S.C. 1531 et seq.). 

Dated: August 29, 2008. 

Kenneth Stansell, 

Acting Director, U.S. Fish and Wildlife 

Service. 

[FR Doc. E8–20674 Filed 9–8–08; 8:45 am] 

BILLING CODE 4310–55–P 


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