Fall and winter movements of and habitat use by cutthroat trout in the Ram River, Alberta
habitat, trout, pool, Substrate
Journal or Book Title
Transactions of the American Fisheries Society
Fall and winter movements of and habitat use by cutthroat trout (Oncorhynchus clarki)were studied with radiotelemetry in low, mid, and high altitudes of a river system to evaluate thetiming and extent of habitat shifts when fish moved from summer feeding areas to overwinteringareas. The movements of 20 fish were monitored from August to November 1991, and 17 fishwere monitored from October to December 1992. Cutthroat trout moved out of summer habitatsin mid-September, and many made a two-stage shift in habitat use from summer to winter thatwas associated with anchor ice formation. When cutthroat trout were excluded from fall habitatsby anchor ice, they moved to overwintering areas less likely to be influenced by frazil and anchorice: deep pools with ice cover or areas where water temperatures were higher than the rest of thestream because of springs or upwelling warm groundwater. Cutthroat trout used deeper waterand smaller diameter substrates in winter than in summer but used less cover during winter.Because of decreases in discharge and exclusion by anchor ice, cutthroat trout were forced intorestricted suitable habitat, which resulted in large aggregations of fish. Cutthroat trout moved 0.0–7.6 km from summer to overwintering areas. They were stationary most of the time; when theydid move, most movements exceeded 100 m. The number of movements made decreased fromsummer to winter.