Yellowstone Cutthroat Trout
Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri; YCT) are the the most widespread native trout of the park and were the dominant fish species here prior to Euroamerican settlement. They are an important species in Yellowstone National Park, upon which many other species depend. They provide an important source of food for an estimated 20 species of birds, and mammals including bears, river otters, and mink. In the recent past, fishing for cutthroat trout has supported a $36 million annual sport fishery.
Genetically pure YCT populations have declined throughout their natural range in the Intermountain West, succumbing to competition with and predation by nonnative fish species, a loss of genetic integrity through hybridization, habitat degradation, predation, and angling harvest. Many of the remaining genetically pure YCT are found within the park. State and federal wildlife agencies classify YCT as a sensitive species. However, the US Fish and Wildlife Service does not warrant listing the YCT as a threatened species under the Endangered Species Act.
The Yellowstone cutthroat trout population in the Yellowstone Lake ecosystem has declined substantially since the mid-1980s. Lake-wide sampling began in 1968 and in 1984 the average number of YCT caught at survey sites reached 19.1 per net. Catch per unit effort increased from an average of 11.8 (8.7–15.0) in 2010 to 28.4 (23.7–33.0) in 2014. The increase in catch each year was primarily due to an influx of young, juvenile cutthroat trout within the system; however, increased catches of large, older-age fish also occurred. Cutthroat trout had a mean total length of 358 millimeters in 2012, 382 millimeters in 2013, and 405 millimeters in 2014. These mean lengths were much lower than those observed in earlier years. In 2014, most (53%) cutthroat trout were large adults between 430 and 620 millimeters in total length, while juveniles and subadults (29%) were less than 325 millimeters in total length.
Monitoring at Clear Creek, a Yellowstone Lake tributary, began in 1945. The number of YCT spawning there peaked at more than 70,000 in 1978 and fell to 538 by 2007. The decline is attributed to predation by nonnative lake trout, low water during drought years, and the nonnative parasite that causes whirling disease.
Two-thirds of the park streams that were part of the species’ native habitat outside the Yellowstone Lake watershed still contain genetically pure YCT; other streams have YCT hybridized with introduced rainbow trout. The objectives of Yellowstone’s Native Fish Conservation Plan (2010) include recovery of YCT abundance in the lake to that documented in the late 1990s, maintaining access for spawning YCT in at least 45 of 59 Yellowstone Lake’s historical spawning tributaries, and maintaining or restoring genetically pure YCT in the current extent of streams occupied by pure or hybrid YCT.
Yellowstone Lake and the Yellowstone River together contain the largest inland population of cutthroat trout in the world. While the Yellowstone cutthroat trout is historically a Pacific drainage species, it has (naturally) traveled across the Continental Divide into the Atlantic drainage. One possible such passage in the Yellowstone area is Two Ocean Pass, south of the park in the Teton Wilderness. Here, it’s possible that fish swam across the Continental Divide at the headwaters of Pacific Creek and Atlantic Creek and, thus, swam from the Pacific to the Atlantic watersheds.
Restoring YCT to park waters is an important component of the Native Fish Conservation Plan. In 2012, park staff began an effort to remove nonnative brook trout from the Elk Creek drainage above a natural fish barrier near the Yellowstone River. This project will require multiple years of nonnative fish removal before YCT can be introduced, but the project is an opportunity to replicate rare small-stream resident YCT in the park. Further efforts to restore and conserve YCT are occurring in the Lamar River Drainage where a barrier to protect upper Soda Butte Creek was constructed in 2013 and similar barriers are being considered for Slough Creek and the upper Lamar River. Continue: Westslope Trout
Number in Yellowstone
The number of Yellowstone cutthroat trout spawning at Clear Creek, a Yellowstone Lake tributary where monitoring began in 1945, peaked at more than 70,000 in 1978 and fell to 538 by 2007.
Where to See
Yellowstone Lake, Fishing Bridge, LeHardy's Rapids, Trout Lake
Red jaw slash
The Yellowstone Resources and Issues Handbook, updated annually, is the book our rangers use to answer many basic park questions.
2009. Yellowstone cutthroat trout: Conserving a heritage population in Yellowstone Lake. Mammoth Hot Springs, WY: National Park Service.
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. Life-history 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.