Fall and Winter Movements of and Habitat Use by Cutthroat Trout in the Ram River, Alberta

Abstract

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 the timing and extent of habitat shifts when fish moved from summer feeding areas to overwintering areas. The movements of 20 fish were monitored from August to November 1991, and 17 fish were monitored from October to December 1992. Cutthroat trout moved out of summer habitats in mid‐September, and many made a two‐stage shift in habitat use from summer to winter that was associated with anchor ice formation. When cutthroat trout were excluded from fall habitats by anchor ice, they moved to overwintering areas less likely to be influenced by frazil and anchor ice: deep pools with ice cover or areas where water temperatures were higher than the rest of the stream because of springs or upwelling warm groundwater. Cutthroat trout used deeper water and 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 into restricted 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 they did move, most movements exceeded 100 m. The number of movements made decreased from summer to winter.

Winter Disturbances and Riverine Fish in Temperate and Cold Regions

“…as has been demonstrated for cutthroat trout that were excluded from overwintering pools by extensive anchor ice growth (Brown RS and Mackay 1995).…”

“…Fish use refugia from winter disturbances over various periods of time, ranging from the duration of the disturbance event (Harvey et al 1999) to the remaining winter months (Brown RS and Mackay 1995). The duration of use depends on at least two factors: refuge connectivity and refuge persistence.…”

“…If a refuge is hydrologically connected to the residential habitats of the fish, its quality, which is always relative to the quality of the residential habitats, will determine the duration of refuge use. For instance, cutthroat trout were permanently excluded by excessive anchor ice growth from cover-rich pools that they had occupied in the fall (Brown RS and Mackay 1995). The fish retreated to habitats that are less likely to be affected by subsurface ice, such as groundwater-influenced areas and deep, ice-covered pools, where they stayed until spring.…”

“…The fish retreated to habitats that are less likely to be affected by subsurface ice, such as groundwater-influenced areas and deep, ice-covered pools, where they stayed until spring. These refugia were considered less-preferred winter habitats, because the fish had moved past them in the fall (Brown RS and Mackay 1995). The duration of refuge use also reflects species-specific habitat preferences.…”

Coeur d'Alene Tribe Fisheries Program : Implementation of Fisheries Enhancement Opportunities on the Coeur d’Alene Reservation : 2007 Annual Report.

“…Given that the Lake Creek trap was operational in February of 2007, this indicates that substantial movements would have had to occurred during late fall or early winter. Although fall and winter movements by cutthroat trout have been documented in other studies (Jakober et al 1988;Brown 1999;Brown and Mackay 1995;Lindstrom and Hubert 2004), most of the reported movements were extensive downriver migrations to deep pools that provided suitable overwintering habitats or shorter excursions to avoid adverse conditions (e.g., anchor ice formation). Protracted upriver spawning migrations, however, have been observed for sea-run coastal cutthroat, with some populations exhibiting bimodal peaks in migration timing separated by at least two months (Johnson et al 1999).…”