Fall and early winter movements of cutthroat trout, Oncorhynchus clarki, in relation to water temperature and ice conditions in Dutch Creek, Alberta

Fall and winter movement and behaviour of 28 cutthroat trout Oncorhynchus c larki was determined using radiotelemetry to evaluate the effects of water temperature and ice conditions. As water temperatures decreased, cutthroat trout moved from more solitary positions to aggregations. With few exceptio ns, radiotagged fish aggregated with other fish in groups varying from 5 to approximately 70 fish. The percentage of fish aggregating and the mean siz e of aggregation was negatively correlated with water temperature. The mean distance moved by radiotagged cutthroat trout from 1 September to 12 Janua ry was 1.0 km. After forming aggregations, fish tended to stay within a 120 m length of stream until the end of tracking in mid-January. Fish that wer e less sedentary after their initial overwintering movement usually moved w hen their habitat was occluded by anchor ice. These fish moved thirty times farther and six times more often than fish in stable overwintering areas. In Dutch Creek multiple freezing events caused several ice related habitat exclusions and movements associated with large decreases in air temperature . Several bull trout and mountain whitefish were observed in groups with cu tthroat trout.