Westslope Cutthroat Trout Range Expansion

Recovery of westslope cutthroat trout (WSCT) in Alberta requires recolonization and expansion of their range, which is currently 5% of the historical distribution. Recovery of the species requires strong protections for existing populations, as well as recolonization and expansion of their current range. Invasive species are among the biggest contributors to WSCT declines through hybridization and competition, and the subsequent population fragmentation incurred when neighbouring watersheds become dominated by hybridized and invasive species. Since 2018, we have been adapting a framework originally developed by researchers for bull trout into a framework for WSCT range expansion feasibility in Alberta, into habitat reaches that are secure from invasion, above barriers. We are nearing the completion of compiling information to score habitats and develop candidate lists best suited for WSCT range expansion, as well as investigating watersheds adjacent to WSCT core areas to determine expansion potential and limitations. To date, we have established summer stream temperatures as a strong predictor of WSCT abundance and a measure of candidate habitat quality. In 2021, we completed stream temperature monitoring in the Oldman River, Bow River, and Crowsnest River watersheds and calculated respective summer growing degree days (SGDD) to aid in the final rankings of candidate habitats. In-stream temperature in core areas spanned a range of 921 SGDD, from coolest conditions and lower productivity in Lyall Creek (384 SGDD) (Upper Oldman River watershed) to warmer conditions with higher productivity in Sullivan Creek (1,305 SGDD). Average daily temperatures also reached, and briefly exceeded WSCT tolerances in core areas during 2021 summer temperature extremes. We continue to pursue opportunities for collaborative WSCT range expansion projects at candidate locations across the WSCT range.


Alberta Environment and Parks, Fisheries and Oceans Canada through the Canada Nature Fund

Annual Summaries

Title Year Category
Westslope Cutthroat Trout Population Monitoring in the Upper Oldman River Core Area Range Expansion 2021-2022 1