Westslope Cutthroat Trout
Fish
Upper Bow drainage
The Westslope Cutthroat Trout (Oncorhynchus clarkii lewisi) is native to the cold streams and lakes of the upper Bow River drainage in Banff National Park. It is listed as Threatened under the federal Species at Risk Act (SARA) due to historical overharvesting, habitat fragmentation, and hybridization with non-native Rainbow Trout.
Identification. Distinguished by a red slash beneath the lower jaw. Requires pristine, cold water (6–15°C) with complex cover such as undercut banks, boulders, and riparian vegetation. Genetically pure populations (≥0.99 purity) now occupy less than 5% of their original range in Alberta.
Conservation. Parks Canada has undertaken restoration projects such as the Hidden Lake Restoration Project near Lake Louise; using Rotenone to remove invasive Brook Trout from the lake and upper Corral Creek, followed by reintroduction of pure Westslope Cutthroat via remote stream-side incubation. The upper Bow headwaters are increasingly valued as thermal refugia as climate change warms downstream reaches.