Westslope Cutthroat Trout

A fish on a black background

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

Jay Fleming


Historically the most abundant and widely distributed subspecies of cutthroat trout throughout the West, the westslope cutthroat trout (Onchorhynchus clarkii lewisi, WCT) 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, WCT were nearly eliminated from park streams because of the stocking of competing trout (nonnative brook and brown trout) and interbreeding with nonnative rainbow and 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.


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 WCT have only persisted in one tributary of the Madison River drainage (Last Chance Creek), and in the Oxbow/Geode Creek complex where they were introduced in the 1920s. In 2006, Yellowstone began efforts to restore WCT in East Fork Specimen Creek and High Lake by constructing a fish barrier, removing nonnative fish, and stocking genetically pure WCT. Stocking was completed in High Lake in 2009, and in East Fork Specimen Creek in 2012. Evidence suggests those populations are rapidly becoming established. Another restoration project is designed to create an Upper Missouri River WCT brood stock in Goose Lake, where nonnative fish removal was conducted in 2011 and stocking of fry began in 2013. The largest WCT restoration effort in Yellowstone is the Grayling Creek project (See Arctic grayling), which will restore WCT to over 20 miles of native habitat. Learn More: Native Fish, Mountain Whitefish...


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