Westslope Cutthroat Trout

Westslope cutthroat trout laying on grass
Westslope cutthroat trout are one of 11 native species in Yellowstone National Park.

NPS/Todd Koel


Historically the most abundant and widely distributed subspecies of cutthroat trout throughout the West, the westslope cutthroat trout (Onchorhynchus clarkii lewisi) occupies less than 5% of its former range in the upper Missouri River drainage. It evolved from a common ancestor of the Yellowstone form of the species, and shares their food and habitat requirements. By the 1930s, westslope cutthroat trout were nearly eliminated from park streams because of the stocking of competing trout (nonnative brook and brown trout) and interbreeding with nonnative rainbow trout and native Yellowstone cutthroat trout species. In most of its remaining habitat (an estimated 64% of the approximately 641 stream miles it once occupied in the park), it exists only in a hybridized form.


  • Red slash along jaw and fine spots, common to all cutthroat varieties, along top and tail.
  • Greenish gray in color.
  • Larger, irregular spots along lateral line and toward gills and head.
  • Crimson streak above the belly.
  • Sometimes mistaken for rainbow trout.


  • Genetically pure population only exists in Last Chance Creek and Oxbow/Geode Ck complex.
  • Restored populations growing in the East Fork Specimen and Grayling creeks and Goose and High lakes.
  • Hybridized populations found in many river drainages.
Barrier on East Fork Specimen Creek creates a waterfall along the creek
Barrier on East Fork Specimen Creek prevents nonnative fish from invading restoration area.




Integral to our native species restoration program is having brood sources from which to reestablish native populations. A brood should be accessible, secure from contamination, self-sustaining, genetically diverse, abundant, of traceable origin, and pose no risk to existing wild populations.

Genetically pure westslope cutthroat trout have only persisted in one tributary of the Madison River drainage (now called Last Chance Creek), and in the Oxbow/Geode Creek complex where they were introduced in the 1920s. In 2006, Yellowstone began efforts to restore westslope cutthroat trout in East Fork Specimen Creek and High Lake by constructing a fish barrier, removing hybridized and nonnative fish, and stocking genetically pure westslope cutthroat trout. Stocking was completed in High Lake in 2009, and in East Fork Specimen Creek in 2013. In 2015, several surveys conducted throughout East Fork Specimen Creek indicated a natural reproducing population of westslope cutthroat trout, with all fish appearing healthy. The long-term goal for this watershed is to integrate East Fork Specimen Creek into a larger westslope cutthroat trout restoration project that includes the North Fork to improve the resilience of this isolated population to natural threats.

Another restoration project is being conducted in Goose Lake and two other small, historically fishless lakes in the Firehole drainage. Nonnative fish removal was conducted in 2011 and staff stocked fry from 2013 to 2015. In 2016 an overnight population survey yielded 12 fish around 7 inches long. The long-term project goal is to one day use this pure westslope population as a brood source, providing offspring for restoration projects elsewhere within the upper Missouri River system.

The largest westslope cutthroat trout restoration effort in Yellowstone is the Grayling Creek project (See: Arctic grayling), which will restore westslope cutthroat trout to over 20 miles of native habitat. Future projects for westslope cutthroat trout and fluvial grayling include native fish restoration in North Fork Specimen and Cougar creeks as well as the upper Gibbon River. Once these projects are completed, an additional 61 kilometers (38 miles) of stream will be restored to native fish.

An underwater view of a spotted fish with a red slash on its neck and side swims above pebbles

Fish and Aquatic Species

Native fish underpin natural food webs and have great local economic significance.

Young cutthroat trout in a shallow creek

Fisheries & Aquatic Sciences Program

Explore the National Park Service science program for fish and aquatic species.

Three spotted fish with red jaws underwater

Yellowstone Cutthroat Trout

Yellowstone cutthroat trout are the most widespread native fish in the park.

A gray fish with ark spots and dark stripes on fins

Arctic Grayling

Arctic grayling dwell entirely in streams.

A silvery fish laying on a gray rock

Mountain Whitefish

Lives in rivers and streams with deep pools, clear and clean water.

A gray fish with dark sports and striped fins underwater

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A longnose dace floating above the sandy river bottom


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A longnose sucker along the sandy river bottom


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Angler fishing in Yellowstone


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Baril, L.M., D.W. Smith, T. Drummer, and T.M. Koel. 2013. Implications of cutthroat trout declines for breeding opsreys and bald eagles at Yellowstone Lake. Journal of Raptor Research 47(3): 234–245.

Bigelow, P.E., T.M. Koel, D. Mahony, B. Ertel, B. Rowdon, and S.T. Olliff. 2003. Protection of native Yellowstone cutthroat trout in Yellowstone Lake, Yellowstone National Park, Wyoming, Edited by US Department of the Interior, National Park Service. Fort Collins, CO: National Park Service, Water Resources Division.

Gresswell, R.E. and J.D. Varley. 1988. Effects of a century of human influence on the cutthroat trout of Yellowstone Lake. In R.E. Gresswell, ed., Status and management of interior stocks of cutthroat trout, 45–52. Vol. Symposium 4. American Fisheries Society.

Gresswell, R.E., W.J. Liss, and G.L. Larson. 1994. Lifehistory organization of Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri) in Yellowstone Lake. Canadian Journal of Fisheries and Aquatic Sciences 51(S1):298–309.

Gresswell, R.E. 1995. Yellowstone cutthroat trout. In M. K. Young, ed., Conservation assessment for inland cutthroat trout, 36–54. Fort Collins, CO: US Forest Service, Rocky Mountain Forest and Range Experiment Station.

Heckmann, R. 1994. Cutthroats and parasites: Yellowstone Lake’s complex community of fish and companion organisms. Yellowstone Science 2(3).

Kerkvliet, J., C. Nowell, and S. Lowe. The economic value of a predator: Yellowstone trout. In A. P. Curlee, A. Gillesberg and D. Casey, ed., Greater Yellowstone predators: Ecology and conservation in a changing landscape: Proceedings of the third biennial conference on the Greater Yellowstone Ecosystem, 143–150. Yellowstone National Park, WY: Northern Rockies Conservation Cooperative and Yellowstone National Park.

Koel, T.M., P.E. Bigelow, P.D. Doepke, B.D. Ertel, and D.L. Mahony. 2005. Nonnative lake trout result in Yellowstone cutthroat trout decline and impacts to bears and anglers. Fisheries 30(11):10–19.

Koel, T.M., P.E. Bigelow, P.D. Doepke, B.D. Ertel, and D.L. Mahoney. 2006. Conserving Yellowstone cutthroat trout for the future of the Greater Yellowstone Ecosystem: Yellowstone’s Aquatic Sciences Program. Yellowstone Science 14(2).

Koel, T.M., D.L. Mahony, K.L. Kinnan, C. Rasmussen, C.J. Hudson, S. Murcia, and B.L. Kerans. 2006. Myxobolus cerebralis in native cutthroat trout of the Yellowstone Lake ecosystem. Journal of Aquatic Animal Health 18(3):157–175.

May, B.E., W. Urie, and B.B. Shepard. 2003. Range-wide status of Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri): 2001, Edited by US Forest Service, Montana Fish, Wildlife and Parks, Montana Cooperative Fishery Research Unit. Bozeman, MT.

National Park Service, Yellowstone National Park. 2010. Native Fish Conservation Plan / Environmental Assessment, Edited by Department of the Interior. Yellowstone Center for Resources.

Reinhart, D.P., S.T. Olliff, and K.A. Gunther. Managing bears and developments on cutthroat spawning streams in Yellowstone National Park. In A.P. Curlee, A. Gillesberg and D. Casey, ed., Greater Yellowstone predators: Ecology and conservation in a changing landscape: Proceedings of the third biennial conference on the Greater Yellowstone Ecosystem, 161–169. Yellowstone National Park, WY: Northern Rockies Conservation Cooperative and Yellowstone National Park.

Varley, J.D. and P. Schullery. 1995. The Yellowstone Lake crisis: Confronting a lake trout invasion: a report to the director of the National Park Service. Yellowstone National Park, WY: National Park Service, Yellowstone Center for Resources.

Last updated: April 19, 2017

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