Oncorhynchus clarkii lewisi - (Girard, 1856)
Westslope Cutthroat Trout
Taxonomic Status: Accepted
Related ITIS Name(s): Oncorhynchus clarkii lewisi (Girard, 1856) (TSN 553415)
Unique Identifier: ELEMENT_GLOBAL.2.103630
Element Code: AFCHA02088
Informal Taxonomy: Animals, Vertebrates - Fishes - Bony Fishes - Salmon and Trouts
 
Kingdom Phylum Class Order Family Genus
Animalia Craniata Actinopterygii Salmoniformes Salmonidae Oncorhynchus
Genus Size: C - Small genus (6-20 species)
Check this box to expand all report sections:
Concept Reference
Help
Concept Reference: Smith, G. R., and R. F. Stearley. 1989. The classification and scientific names of rainbow and cutthroat trouts. Fisheries (Bethesda) 14(1):4-10.
Concept Reference Code: A89SMI01NAUS
Name Used in Concept Reference: Oncorhynchus clarkii lewisi
Taxonomic Comments: According to Allendorf and Leary (1988), coastal, Lahontan, and westslope subspecies of O. clarkii are electrophoretically divergent from other subspecies, closer to rainbow trout. However, mtDNA comparisons agree with other systematic and zoogeographical evidence that all subspecies of cutthroat trout are more closely related to each other than any of them is to rainbow trout (Gyllensten and Wilson 1987). Much of genetic variation within westslope cutthroat (subspecies lewisi) results from alleles found in only one or two local populations (Allendorf and Leary 1988).

Extensive introductions of Yellowstone cutthroat trout have been made in the range of westslope cutthroat trout, and "hybridization" has resulted. In Glacier National Park, hybridization occurred in previously barren lakes into which both subspecies were introduced but did not occur where Yellowstone cutthroats were introduced into areas with native westslope cutthroat populations (Yellowstone cutthroats did not survive) (Behnke 1992). Widespread hybridization with introduced rainbow trout has occurred (but not where cutthroat trout and rainbow trout evolved in sympatry) (McIntyre and Rieman 1995).

Forbes and Allendorf (1991) found that mitochondrial genotypes had no detectable effects on meristic traits in interbreeding trouts of the subspecies lewisi (westslope) and bouvieri (Yellowstone), which exhibit substantial genetic divergence.
Conservation Status
Help

NatureServe Status

Global Status: G4T4
Global Status Last Reviewed: 31May2013
Global Status Last Changed: 31May2013
Ranking Methodology Used: Ranked by calculator
Rounded Global Status: T4 - Apparently Secure
Reasons: Range much reduced but still widespread in British Columbia, Alberta, Washington, Oregon, Idaho, Montana, and Wyoming; currently occupies approximately 54,000 stream-kilometers; many protected and appropriately managed populations; major threat is genetic introgression from introduced exotic fishes.
Nation: United States
National Status: N4 (31May2013)
Nation: Canada
National Status: N3 (09Feb2016)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Colorado (SNA), Idaho (S4), Montana (S2), Oregon (S2), Washington (S2S3), Wyoming (S1)
Canada Alberta (S2), British Columbia (S3)

Other Statuses

Implied Status under the Committee on the Status of Endangered Wildlife in Canada (COSEWIC):T,SC
Comments on COSEWIC: Saskatchewan - Nelson Rivers populations are designated Threatened. Pacific populations are designated Special Concern.
American Fisheries Society Status: Threatened (01Aug2008)

NatureServe Global Conservation Status Factors

Range Extent: 200,000-2,500,000 square km (about 80,000-1,000,000 square miles)
Range Extent Comments: West of the Continental Divide, this subspecies is believed to be native to several major drainages of the Columbia River basin, including the upper Kootenai River drainage from its headwaters in British Columbia, through northwest Montana, and into northern Idaho; the Clark Fork River drainage of Montana and Idaho downstream to the falls on the Pend Oreille River near the Washington-British Columbia border; the Spokane River above Spokane Falls and into Idaho's Coeur d'Alene and St. Joe River drainages; and the Salmon and Clearwater River drainages of Idaho's Snake River basin (USFWS 2003). The native distribution also includes disjunct areas draining the east slope of the Cascade Mountains in Washington (Methow River and Lake Chelan drainages, and perhaps the Wenatchee and Entiat river drainages), the John Day River drainage in northeastern Oregon, and the headwaters of the Kootenai River and several other disjunct regions in British Columbia (USFWS 2003). East of the Continental Divide, the native distribution is believed to include the headwaters of the South Saskatchewan River drainage (United States and Canada); the entire Missouri River drainage upstream from Fort Benton, Montana, and extending into northwest Wyoming; and the headwaters of the Judith, Milk, and Marias rivers, which join the Missouri River downstream from Fort Benton (USFWS 2003).

Behnke (1992) regarded the mountain cutthroat trout of British Columbia (nominal subspecies alpestris) as disjunct populations of O. clarkii leweisi.

Area of Occupancy: >12,500 4-km2 grid cells
Area of Occupancy Comments: USFWS (1999) determined that westslope cutthroat trout then occurred in about 4,275 tributaries or stream reaches that collectively encompassed more than 37,015 kilometers of stream habitat. In addition, the trout were determined to naturally occur in 6 lakes totaling about 72,843 hectares in Idaho and Washington and in at least 20 lakes totaling 2,164 hectares in Glacier National Park in Montana (USFWS 1999). These totals included areas containing potentially introgressed westslope cutthroat trout populations and populations with unknown genetic characteristics (USFWS 2003).

Shepard et al. (2005) determined that this subspecies occupies 54,000 stream-kilometers.

Number of Occurrences: > 300
Number of Occurrences Comments: This subspecies is represented by numerous robust populations, including several hundred "conservation" populations (USFWS 1999, 2000, 2003; Shepard et al. 2005; May 2009).

Population Size: 100,000 to >1,000,000 individuals
Population Size Comments: Total adult population size is unknown but very large.

Overall Threat Impact: Medium
Overall Threat Impact Comments: Hybridization with nonnative rainbow trout or their hybrid progeny and descendants, both of which have established self-sustaining populations in many areas in the range westslope cutthroat trout, remains the greatest threat to westslope cutthroat trout (USFWS 2003). The available empirical evidence and speculations of many fishery scientists indicate that introgression of rainbow trout genes will continue to move upstream into many stream reaches presently inhabited by westslope cutthroat trout, although there may be limits to that upstream spread set by environmental factors and the superior fitness of extant westslope cutthroat trout populations in their native habitats. The eventual extent that such hybridization moves upstream may be stream-specific and impossible to predict (USFWS 2003). However, numerous nonintrogressed westslope cutthroat trout populations are distributed in secure habitats throughout the subspecies' historical range. USFWS (2003) considered slightly introgressed westslope cutthroat trout populations, with low amounts of genetic introgression detectable only by molecular genetic methods, to be a potentially important and valued component of the overall westslope cutthroat trout subspecies. USFWS (2003) concluded that westslope cutthroat trout are not threatened by introgressive hybridization. Genetic analyses found no evidence of genetic introgression in 768 samples (58 percent of samples tested) (the numbers of individuals tested per sample were variable and sample sites were not randomly selected) (Shepard et al. 2005).

Impacts of introduced kokanee, lake trout, and brook trout have eliminated populations in some areas (e.g., kokanee may outcompete cutthroat for zooplankton, lake trout is an effective predator on cutthroat). Some westslope cutthroat trout populations have persisted despite the presence of large kokanee populations (see McIntyre and Rieman 1995). Lake whitefish and non-native mysid shrimp also evidently have caused cutthroat declines through competitive interactions. However, USFWS (2000, 2003) concluded that extant headwater populations of westslope cutthroat trout are relatively secure from colonization by non-native fishes (and from adverse effects of human activities).

Stocked, hatchery-reared steelhead that do not migrate to the ocean (residual steelhead) sometimes migrate over 12 km upstream from their release point and may move into areas occupied by westslope cutthroat trout (McMichael and Pearsons 2001). Locally, residual steelhead could pose a threat through ecological interactions.

This subspecies has been negatively affected by loss/degradation of habitat from logging, road construction, mining, and grazing (Spahr et al. 1991), which may result in sedimentation and increased water temperature . Habitat loss has been a primary cause of depressed populations in Idaho (McIntyre and Rieman 1995). These fishes are sensitive to pollution and generally to siltation of streams (some populations may persist despite abundant sediment). Dams, irrigation diversions, and other migration barriers have negatively affected habitat and probably have interfered with metapopulation dynamics (McIntyre and Rieman 1995). Populations have become increasingly fragmented. However, many populations exist in streams that are not affected by these factors (USFWS 2003).

Westslope cutthroat trout are sensitive to fishing pressure (McIntyre and Rieman 1995); restricted or catch-and-release fishing has been needed to maintain wild populations (Spahr et al. 1991). Climate warming would eliminate some habitat.

Overall, USFWS (2000, 2003) concluded that the magnitude and imminence of existing threats are small.

Short-term Trend: Decline of 10-30%
Short-term Trend Comments: Trend over the past 10 years or three generations is uncertain, but area of occupancy and abundance probably have been slowly declining.

Shepard et al. (2005) concluded that while the distribution of westslope cutthroat trout has declined dramatically from historical levels, the subspecies is not currently at imminent risk of extinction because (1) it is still widely distributed, especially in areas protected by stringent land use restrictions; (2) many populations are isolated by physical barriers from invasion by nonnative fish and disease; and (3) active conservation of many populations is occurring.

Long-term Trend: Decline of 30-50%
Long-term Trend Comments: Westslope cutthroat trout historically occupied 90,800 stream-kilometers and currently occupy 54,600 kilometers (however, these are probably underestimates) (Shepard et al. 2005).

Other NatureServe Conservation Status Information

Distribution
Help
Global Range: (200,000-2,500,000 square km (about 80,000-1,000,000 square miles)) West of the Continental Divide, this subspecies is believed to be native to several major drainages of the Columbia River basin, including the upper Kootenai River drainage from its headwaters in British Columbia, through northwest Montana, and into northern Idaho; the Clark Fork River drainage of Montana and Idaho downstream to the falls on the Pend Oreille River near the Washington-British Columbia border; the Spokane River above Spokane Falls and into Idaho's Coeur d'Alene and St. Joe River drainages; and the Salmon and Clearwater River drainages of Idaho's Snake River basin (USFWS 2003). The native distribution also includes disjunct areas draining the east slope of the Cascade Mountains in Washington (Methow River and Lake Chelan drainages, and perhaps the Wenatchee and Entiat river drainages), the John Day River drainage in northeastern Oregon, and the headwaters of the Kootenai River and several other disjunct regions in British Columbia (USFWS 2003). East of the Continental Divide, the native distribution is believed to include the headwaters of the South Saskatchewan River drainage (United States and Canada); the entire Missouri River drainage upstream from Fort Benton, Montana, and extending into northwest Wyoming; and the headwaters of the Judith, Milk, and Marias rivers, which join the Missouri River downstream from Fort Benton (USFWS 2003).

Behnke (1992) regarded the mountain cutthroat trout of British Columbia (nominal subspecies alpestris) as disjunct populations of O. clarkii leweisi.

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.

Map unavailable!:
Distribution data for U.S. states and Canadian provinces is known to be incomplete or has not been reviewed for this taxon.
Endemism: occurs (regularly, as a native taxon) in multiple nations

U.S. & Canada State/Province Distribution
United States COexotic, ID, MT, OR, WA, WY
Canada AB, BCnative and exotic

Range Map
No map available.


U.S. Distribution by County Help
State County Name (FIPS Code)
MT Beaverhead (30001), Broadwater (30007), Carbon (30009), Cascade (30013), Chouteau (30015), Daniels (30019), Dawson (30021), Deer Lodge (30023), Fallon (30025), Fergus (30027), Flathead (30029), Gallatin (30031), Glacier (30035), Granite (30039), Jefferson (30043), Judith Basin (30045), Lake (30047), Lewis and Clark (30049), Lincoln (30053), Madison (30057), Meagher (30059), Mineral (30061), Missoula (30063), Park (30067), Pondera (30073), Powell (30077), Ravalli (30081), Sanders (30089), Silver Bow (30093), Sweet Grass (30097), Teton (30099), Wheatland (30107)
OR Grant (41023)
WY Park (56029), Teton (56039)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
09 St. Marys (09040001)+, Belly (09040002)+
10 Red Rock (10020001)+, Beaverhead (10020002)+, Ruby (10020003)+, Big Hole (10020004)+, Jefferson (10020005)+, Boulder (10020006)+, Madison (10020007)+, Gallatin (10020008)+, Upper Missouri (10030101)+, Upper Missouri-Dearborn (10030102)+, Smith (10030103)+, Sun (10030104)+, Belt (10030105)+, Two Medicine (10030201)+, Cut Bank (10030202)+, Marias (10030203)+, Teton (10030205)+, Arrow (10040102)+, Judith (10040103)+, Upper Musselshell (10040201)+, Flatwillow (10040203)+, Box Elder (10040204)+, Poplar (10060003)+, Yellowstone Headwaters (10070001)+*, Upper Yellowstone (10070002)+, Stillwater (10070005)+, Clarks Fork Yellowstone (10070006)+, Lower Yellowstone (10100004)+, O'fallon (10100005)+
17 Upper Kootenai (17010101)+, Fisher (17010102)+, Yaak (17010103)+, Lower Kootenai (17010104)+, Moyie (17010105)+, Elk (17010106)+, Upper Clark Fork (17010201)+, Flint-Rock (17010202)+, Blackfoot (17010203)+, Middle Clark Fork (17010204)+, Bitterroot (17010205)+, North Fork Flathead (17010206)+, Middle Fork Flathead (17010207)+, Flathead Lake (17010208)+, South Fork Flathead (17010209)+, Stillwater (17010210)+, Swan (17010211)+, Lower Flathead (17010212)+, Lower Clark Fork (17010213)+, Upper Henrys (17040202)+, Upper North Fork Clearwater (17060307)+, Upper John Day (17070201)+, North Fork John Day (17070202)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
Help
Basic Description: A cutthroat trout.
General Description: A trout with small, nonrounded spots, with few spots on the anterior body below the lateral line; coloration varies, but generally is silver with yellowish hints, though bright yellow, orange, and especially red colors can be expressed to a much greater extent than on coastal or Yellowstone cutthroat (Behnke 1992). Hybridization between westslope and Yellowstone cutthroat trout can produce a spectrum of spotting and coloration ranging between the typical patterns of each subspecies. Some populations that have been affected by hybridization show little or no phenotypic signs of hybridization (Behnke 1992). Hybridization with rainbow trout can be detected by the appearance of spots on the top of the head and on the anterior body below the lateral line, as well as by reduced scale counts, increased caecal counts, and loss of basibranchial teeth (see Behnke 1992).
Diagnostic Characteristics: Montana: both pure and moderately hybridized populations of westslope cutthroat trout have a high incidence of basibranchial teeth, whereas pure rainbow trout lack these teeth; presence of basibranchial teeth in some individuals of a rainbow trout population indicates hybridization with westslope cutthroat trout (Leary et al. 1996).
Reproduction Comments: Spawns March-July, depending on elevation, at water temperatures near 10 C; usually first spawns at age 4 or 5; alternate-year spawning has been reported in the Flathead River basin in Montana and elsewhere; repeat spawners may comprise up to about 24% of the adult population (Spahr et al. 1991, McIntyre and Rieman 1995).

In the Blackfoot River drainage, Montana, fishes spawned as flows subsided after the peak discharge; 38% of individuals died after spawning (Schmetterling 2001).

Ecology Comments: Metapopulation theory may apply to this species (see McIntyre and Rieman 1995).
Habitat Type: Freshwater
Non-Migrant: Y
Locally Migrant: Y
Long Distance Migrant: N
Mobility and Migration Comments: Resident populations spend entire life in small stream; migratory cutthroat may travel about 25-50 miles between breeding and nonbreeding habitats (Spahr et al. 1991). Trout from large lakes such as Coeur d'Alene, Priest, Pend Oreille, and Flathead lakes may migrate 150 km or more between spawning (upstream) and nonspawning (lake) habitats (Behnke 1992). Extent of migrations may vary with the availability of high quality pools suitable for overwintering. See also reproduction comments.

In the Blackfoot River drainage (Montana), 16 of 22 radio-tagged individuals migrated during the spawning period; migrations to tributaries occurred during the rising limb of the hydrograph; migratory fishes moved both upriver and downriver to reach spawning tributaries; in one year the mean distance traveled to access tributaries was 31 km (range 3-72 km); once in tributaries, individuals generally remained within a 200-m reach; neither of two repeat migrants spawned within 3 km of the previous year's spawning location, though both traveled in the same tributaries; after leaving tributaries fishes moved both upriver and downriver to overwintering areas and did not move more than 100 m thereafter; individuals did not exhibit fidelity to their prespawning main-stem locations; in general, fishes demonstarted the large spatial extent over which fluvial westslope cutthroat trout use aquatic resources (Schmetterling 2001).

Riverine Habitat(s): CREEK, High gradient, MEDIUM RIVER, Moderate gradient, Pool, Riffle
Lacustrine Habitat(s): Deep water, Shallow water
Special Habitat Factors: Benthic
Habitat Comments: Small mountain streams, main rivers, and large natural lakes; requires cool, clean, well-oxygenated water; in rivers, adults prefer large pools and slow velocity areas (stream reaches with numerous pools and some form of cover generally have the highest fish densities); often occurs near shore in lakes (Spahr et al. 1991). Juveniles of migratory populations may spend 1-4 years in their natal streams, then move (usually in spring or early summer, and/or in fall in some systems) to a main river or lake where they remain until they spawn (Spahr et al. 1991, McIntyre and Rieman 1995). Many fry disperse downstream after emergence (McIntyre and Rieman 1995). Juveniles tend to overwinter in interstitial spaces in the substrate. Larger individuals congregate in pools in winter.

Spawns in small tributary streams on clean gravel substrate; mean water depth is 17-20 cm and mean water velocity is 0.3-0.4 m/sec; tends to spawn in natal stream (see McIntyre and Rieman 1995). Adfluvial populations live in large lakes in the upper Columbia drainage and spawn in lake tributaries. Fluvial populations live and grow in rivers and spawn in tributaries. Resident populations complete the entire life history in tributaries. All three life-history forms may occur in a single basin (McIntyre and Rieman 1995). Migrants may spawn in the lower reaches of the same streams used by resident fishes. Maturing adfluvial fishes move into the vicinity of tributaries in fall and winter and remain there until they begin to migrate upstream in spring. Of migratory spawners, some remain in tributaries during summer months but most return to the main river or lake soon after spawning (Behnke 1992).

Adult Food Habits: Invertivore
Immature Food Habits: Invertivore
Food Comments: Feeds mainly on aquatic and terrestrial insects and zooplankton; diet includes relatively few fishes (Spahr et al. 1991, McIntyre and Rieman 1995).
Economic Attributes Not yet assessed
Help
Management Summary
Help
Stewardship Overview: Effective conservation probably will require the maintenance or restoration of well-connected mosaics of habitat (see McIntyre and Rieman 1995).

Restoration should focus on rehabilitating degraded watersheds and removing/excluding undesirable non-native fishes (Van Eimeren 1996).

Schmetterling (2001) recommended for the Blackfoot river drainage in western Montana riparian timber management that continues long-term input of large woody debris to tributaries, continued closure of the Blackfoot River to angling harvest, and the use of culvert designs that will pass spawning fishes under most flow conditions.

Relatively little is known about the appropriate amount or distribution of habitat necessary to ensure long-term persistence of populations. Larger scale patterns in habitat and fish distribution, dispersal rates and mechanisms, and disturbance regimes need to be considered (McIntyre and Rieman 1995). More effective measures of habitat suitability are needed (McIntyre and Rieman 1995). More information is needed on the roles of the different life-history forms in the long-term persistence of populations (McIntyre and Rieman 1995).

Population/Occurrence Delineation Not yet assessed
Help
Population/Occurrence Viability
Help
U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
Help
Authors/Contributors
Help
NatureServe Conservation Status Factors Edition Date: 31May2013
NatureServe Conservation Status Factors Author: Hammerson, G.
Management Information Edition Date: 10Feb2003
Element Ecology & Life History Edition Date: 10Feb2003
Element Ecology & Life History Author(s): Hammerson, G.

Zoological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).

References
Help
  • Allendorf, F. W., and R. F. Leary. 1988. Conservation and distribution of genetic variation in a polytypic species, the cutthroat trout. Conservation Biology 2:170-184.

  • B.C. Ministry of Environment. 2013j. Management plan for the Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi) in British Columbia. B.C. Ministry of Environment, Victoria, BC. 99 pp.

  • B.C. Ministry of Environment. Recovery Planning in BC. B.C. Minist. Environ. Victoria, BC. Available: http://www.env.gov.bc.ca/wld/recoveryplans/rcvry1.htm

  • Bear E.A., T.E. McMahon, A.V. Zale. 2007. Comparative Thermal Requirements of Westslope Cutthroat Trout and Rainbow Trout: Implications for Species Interactions and Development of Thermal Protection Standards. Transactions of the American Fisheries Society 136: 1113-1121 . 

  • Behnke, R. J. 1992. Native trout of western North America. American Fisheries Society Monograph 6. xx + 275 pp.

  • COSEWIC. 2006q. COSEWIC assessment and update status report on the westslope cutthroat trout Oncoryhnchus clarkii lewisi (British Columbia population and Alberta population) in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vii + 67pp.

  • Claire, Errol. 1993. ODFW Northeast Regional Fish Management Meeting. Review of T& E Sensitive and Stocks of Concern. Westslope Cutthroat Trout.

  • Costello, A. and E. Rubidge. 2003b (draft). COSEWIC status report on cutthroat trout (Oncorhynchus spp.). Prepared for Committee on the Status of Endangered Wildlife in Canada. 68 pp.

  • Downs, C. C. 1995. Age determination, growth, fecundity, age at sexual maturity, and longevity for isolated, headwater populations of westslope cutthroat trout. M.S. Thesis, Montana State University, Bozeman. 81 pp.

  • Duff, D. 1996. Bonneville cutthroat trout ONCORHYNCHUS CLARKI UTAH. Pages 35-73 in D. Duff, technical editor. Conservation assessment for inland cutthroat trout: distribution, status and habitat management implications. USDA Forest Service, Intermountain Region, Ogden, Utah.

  • Fisheries and Oceans Canada. 2017c. Management Plan for the Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi), British Columbia Population, in Canada. Species at Risk Act Management Plan Series. Fisheries and Oceans Canada, Ottawa. iv + 116 pp.

  • Forbes, S. H., and F. W. Allendorf. 1991a. Mitochondrial genotypes have no detectable effects on meristic traits in cutthroat trout hybrid swarms. Evolution 45:1350-1359.

  • Gyllensten, U., and A. C. Wilson. 1987. Mitochondrial DNA of salmonids: inter- and intraspecific variability detected with restriction enzymes. Pages 301-317 in N. Ryman and F. Utter, editors. Population genetics and fishery management. University of Washington Press, Seattle.

  • Hagen, J. and J.T.A. Baxter. 2009. 2008 westslope cutthroat trout population abundance monitoring of classified waters in the East Kootenay region of British Columbia. Prepared for BC Ministry of Environment, Fisheries Program, East Kootenay Region, Cranbrook, BC.

  • Jelks, H. L., S. J. Walsh, N. M. Burkhead, S. Contreras-Balderas, E. Díaz-Pardo, D. A. Hendrickson, J. Lyons, N. E. Mandrak, F. McCormick, J. S. Nelson, S. P. Platania, B. A. Porter, C. B. Renaud, J. Jacobo Schmitter-Soto, E. B. Taylor, and M.L. Warren, Jr. 2008. Conservation status of imperiled North American freshwater and diadromous fishes. Fisheries 33(8):372-407.

  • Leary, R. F., W. R. Gould, and G. K. Sage. 1996. Success of basibranchial teeth in indicating pure populations of rainbow trout and failure to indicate pure populations of westslope cutthroat trout. North American Journal of Fisheries Management 16:210-213.

  • Liknes, G. A., and P. J. Graham. 1988. Westslope cutthroat trout in Montana: life history, status, and management. American Fisheries Society Symposium 4:53-60.

  • May B. E. 2009. Westslope cutthroat trout status update summary. Wild Trout Enterprises LLC, Bozeman, Montana.

  • McIntyre, J. D., and B. E. Rieman. 1995. Westslope cutthroat trout. Pages 1-15 in M. K. Young, technical editor. Concervation assessment for inland cutthroat trout. USDA Forest Service Gen. Tech. Report RM-GTR-256. iv + 61 pp.

  • McMichael, G. A., and T. N. Pearsons. 2001. Upstream movement of residual hatchery steelhead into areas containing bull trout and cutthroat trout. North American Journal of Fisheries Management 21:943-946.

  • McPhail, J.D. 2007. The freshwater fishes of British Columbia. The University of Alberta Press, Edmonton, Alberta.

  • Oliver, G.G. 2009. Towards a westslope cutthroat trout management plan for the province of British Columbia. Prepared for BC Ministry of Environment, Victoria, BC.

  • Page, L. M., and B. M. Burr. 2011. Peterson field guide to freshwater fishes of North America north of Mexico. Second edition. Houghton Mifflin Harcourt, Boston. xix + 663 pp.

  • Peven, C. 2003. Population structure, status and life histories of Upper Columbia steelhead, Spring and Summer/Fall Chinook, sockeye, Coho salmon, bull trout, westslope cutthroat trout, non-migratory rainbow trout, pacific lamprey, and sturgeon. Peven Consulting, Inc. 3617 Burchvale Rd. Wenatchee, WA. 145 pp.

  • Rieman, B., D. Lee, J. McIntyre, K. Overton, and R. Thurow. 1993. Consideration of extinction risks for salmonids. U.S.D.A.. Forest Service Fish Habitat Relationship Technical Bulletin 14. Intermountain Research Station, Boise, ID.

  • Schmetterling, D. A. 2001. Seasonal movements of fluvial westslope cutthroat trout in the Blackfoot River drainage, Montana. North American Journal of Fisheries Management 21:507-520.

  • Shepard, B. B., B. E. May, and W. Urie. 2005. Status and conservation of westslope cutthroat trout within the western United States. North American Journal of Fisheries Management 25: 1426-1440.

  • Smith, G. R., and R. F. Stearley. 1989. The classification and scientific names of rainbow and cutthroat trouts. Fisheries (Bethesda) 14(1):4-10.

  • Spahr, R., L. Armstrong, D. Atwood, and M. Rath. 1991. Threatened, endangered, and sensitive species of the Intermountain Region. U.S. Forest Service, Ogden, Utah.

  • Trotter, PC, B McMillan, N Gayeski, P Spruell, A. Whiteley. 2001. Genetic and phenotypic catalog of native resident trout of the interior Columbia River Basin. Fiscal Year 1999: Populations of the Pend Oreille, Kettle, and Sanpoil river basins of the Colville National Forest. Prepared for Northwest Planning Council. 53 pp.

  • Trotter, PC, B McMillan, N Gayeski, P Spruell, M Cook. 2001. Genetic and phenotypic catalog of native resident trout of the interior Columbia River Basin. Fiscal Year 1998: Populations in the Wenatchee, Entiat, Lake Chelan, and Methow river drainages. Prepared for NW Power Planning Council. 48 pp.

  • Trotter, PC, B McMillan, N Gayeski, P Spruell, R. Burkley. 1999. Genetic and phenotypic catalog of native resident trout of the interior Columbia River Basin. Fiscal Year 1998: Populations of the upper Yakima Basin. Prepared for US Dpt of Energy. 53 pp.

  • U.S. Fish and Wildlife Service (USFWS). 10 June 1998. 90-day finding and commencement of status review for a petition to list the westslope cutthroat trout as threatened. Federal Register 63(111):31691-31693.

  • U.S. Fish and Wildlife Service (USFWS). 14 April 2000. 12-month finding for an amended petition to list the westslope cutthroat trout as threatened throughout its range. Federal Register 65(73):20120-20123.

  • U.S. Fish and Wildlife Service (USFWS). 1999. Status review for westslope cutthroat trout in the United Sattes. Regions 1 and 6. Available at:

  • U.S. Fish and Wildlife Service (USFWS). 7 August 2003. Reconsidered finding for an amended petition to list the westslope cutthroat trout as threatened throughout its range. Federal Register 68(152):46989-47009.

  • Van Eimeren, P. 1996. Westslope cutthroat trout ONCORHYNCHUS CLARKI LEWISI. Pages 1-10 in D. A. Duffy, editor. Conservation assessment for inland cutthroat trout: distribution, status and habitat management implications. USDA Forest Service, Intermountain Region, Ogden, Utah.

  • Western Trout Initiative. 2009. Westslope cutthroat trout status update summary. Prepared by Bruce May, Wild Trout Enterprises. 32 pp.

  • Westslope Cutthroat Trout. 1999. B.C. Fish Facts. Conserv. Sect., Fish. Manage. Branch, B.C. Minist. Fish. 2pp.

Use Guidelines & Citation

Use Guidelines and Citation

The Small Print: Trademark, Copyright, Citation Guidelines, Restrictions on Use, and Information Disclaimer.

Note: All species and ecological community data presented in NatureServe Explorer at http://explorer.natureserve.org were updated to be current with NatureServe's central databases as of March 2018.
Note: This report was printed on

Trademark Notice: "NatureServe", NatureServe Explorer, The NatureServe logo, and all other names of NatureServe programs referenced herein are trademarks of NatureServe. Any other product or company names mentioned herein are the trademarks of their respective owners.

Copyright Notice: Copyright © 2018 NatureServe, 4600 N. Fairfax Dr., 7th Floor, Arlington Virginia 22203, U.S.A. All Rights Reserved. Each document delivered from this server or web site may contain other proprietary notices and copyright information relating to that document. The following citation should be used in any published materials which reference the web site.

Citation for data on website including State Distribution, Watershed, and Reptile Range maps:
NatureServe. 2018. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia. Available http://explorer.natureserve.org. (Accessed:

Citation for Bird Range Maps of North America:
Ridgely, R.S., T.F. Allnutt, T. Brooks, D.K. McNicol, D.W. Mehlman, B.E. Young, and J.R. Zook. 2003. Digital Distribution Maps of the Birds of the Western Hemisphere, version 1.0. NatureServe, Arlington, Virginia, USA.

Acknowledgement Statement for Bird Range Maps of North America:
"Data provided by NatureServe in collaboration with Robert Ridgely, James Zook, The Nature Conservancy - Migratory Bird Program, Conservation International - CABS, World Wildlife Fund - US, and Environment Canada - WILDSPACE."

Citation for Mammal Range Maps of North America:
Patterson, B.D., G. Ceballos, W. Sechrest, M.F. Tognelli, T. Brooks, L. Luna, P. Ortega, I. Salazar, and B.E. Young. 2003. Digital Distribution Maps of the Mammals of the Western Hemisphere, version 1.0. NatureServe, Arlington, Virginia, USA.

Acknowledgement Statement for Mammal Range Maps of North America:
"Data provided by NatureServe in collaboration with Bruce Patterson, Wes Sechrest, Marcelo Tognelli, Gerardo Ceballos, The Nature Conservancy-Migratory Bird Program, Conservation International-CABS, World Wildlife Fund-US, and Environment Canada-WILDSPACE."

Citation for Amphibian Range Maps of the Western Hemisphere:
IUCN, Conservation International, and NatureServe. 2004. Global Amphibian Assessment. IUCN, Conservation International, and NatureServe, Washington, DC and Arlington, Virginia, USA.

Acknowledgement Statement for Amphibian Range Maps of the Western Hemisphere:
"Data developed as part of the Global Amphibian Assessment and provided by IUCN-World Conservation Union, Conservation International and NatureServe."

NOTE: Full metadata for the Bird Range Maps of North America is available at:
http://www.natureserve.org/library/birdDistributionmapsmetadatav1.pdf.

Full metadata for the Mammal Range Maps of North America is available at:
http://www.natureserve.org/library/mammalsDistributionmetadatav1.pdf.

Restrictions on Use: Permission to use, copy and distribute documents delivered from this server is hereby granted under the following conditions:
  1. The above copyright notice must appear in all copies;
  2. Any use of the documents available from this server must be for informational purposes only and in no instance for commercial purposes;
  3. Some data may be downloaded to files and altered in format for analytical purposes, however the data should still be referenced using the citation above;
  4. No graphics available from this server can be used, copied or distributed separate from the accompanying text. Any rights not expressly granted herein are reserved by NatureServe. Nothing contained herein shall be construed as conferring by implication, estoppel, or otherwise any license or right under any trademark of NatureServe. No trademark owned by NatureServe may be used in advertising or promotion pertaining to the distribution of documents delivered from this server without specific advance permission from NatureServe. Except as expressly provided above, nothing contained herein shall be construed as conferring any license or right under any NatureServe copyright.
Information Warranty Disclaimer: All documents and related graphics provided by this server and any other documents which are referenced by or linked to this server are provided "as is" without warranty as to the currentness, completeness, or accuracy of any specific data. NatureServe hereby disclaims all warranties and conditions with regard to any documents provided by this server or any other documents which are referenced by or linked to this server, including but not limited to all implied warranties and conditions of merchantibility, fitness for a particular purpose, and non-infringement. NatureServe makes no representations about the suitability of the information delivered from this server or any other documents that are referenced to or linked to this server. In no event shall NatureServe be liable for any special, indirect, incidental, consequential damages, or for damages of any kind arising out of or in connection with the use or performance of information contained in any documents provided by this server or in any other documents which are referenced by or linked to this server, under any theory of liability used. NatureServe may update or make changes to the documents provided by this server at any time without notice; however, NatureServe makes no commitment to update the information contained herein. Since the data in the central databases are continually being updated, it is advisable to refresh data retrieved at least once a year after its receipt. The data provided is for planning, assessment, and informational purposes. Site specific projects or activities should be reviewed for potential environmental impacts with appropriate regulatory agencies. If ground-disturbing activities are proposed on a site, the appropriate state natural heritage program(s) or conservation data center can be contacted for a site-specific review of the project area (see Visit Local Programs).

Feedback Request: NatureServe encourages users to let us know of any errors or significant omissions that you find in the data through (see Contact Us). Your comments will be very valuable in improving the overall quality of our databases for the benefit of all users.