Researchers used a spatially explicit simulation model that integrates complex individual behaviors of fall-run Chinook salmon and summer-run steelhead trout during migration, responds to variable habitat conditions over a large extent of the Columbia River, and links migration corridor conditions to fish condition outcomes. By simulating several thermalscapes – or a river’s thermal environment – with alternative scenarios of thermal refuge availability, they examined the relative costs and benefits of cold-water refuge use by migrating adult fish. Model outcomes show that cold-water refuges can provide relief from exposure to high water temperatures, but do not substantially help migrating fish to conserve energy. Simulated cooling of the Columbia River decreased reliance on cold-water refuges and there were slight reductions in migratory energy expenditure. This work provides a framework for assessing the contribution of cold-water refuges to the success of migrating fishes.  

Snyder, M.N., Schumaker, N.H., Dunham, J.B., Keefer, M.L., Leinenbach, P., Brookes, A., Palmer, J., Wu, J., Keenan, D.M., Ebersole, J.L., 2020, Assessing contributions of cold-water refuges to reproductive migration corridor conditions for adult salmon and steelhead trout in the Columbia River, USA: Ecohydraulics, https://doi.org/10.1080/24705357.2020.1855086