Cooperative Fish and Wildlife Research Units Program: Montana Fishery
Education, Research and Technical Assistance for Managing Our Natural Resources

Drinan, D. P., A. V. Zale, M. A. H. Webb, M. L. Taper, B. B. Shepard, and S. T. Kalinowski. 2012. Evidence of local adaptation in westslope cutthroat trout. Transactions of the American Fisheries Society 141:872-880.


Understanding local adaptations is a fundamental goal of evolutionary biology and would provide managers information necessary to better protect and conserve species. Salmonids are a useful system for studying local adaptations because they often persist in differing, isolated environments. In addition, their sensitivity to temperature provides a likely characteristic for natural selection to act on. We studied thermal adaptation in four wild populations and one hatchery stock of Oncorhynchus clarkii lewisi (westslope cutthroat trout). Mean summer temperatures of native streams ranged from 6.7 to 11.2 °C. Embryos were collected from the wild and embryonic development, embryonic survival, and juvenile growth were determined. A significant relationship between median embryonic survival and native stream temperatures at warm incubation temperatures was detected (Rank test; P = 0.04) suggesting that populations are thermally adapted to their native streams.