SPATIAL STABILITY OF CUTTHROAT TROUT (ONCORHYNCHUS-CLARKI) IN A SMALL, COASTAL STREAM

Spatial stability and local movement of a cutthroat trout (Oncorhynchus clarki) population were studied from winter to late summer in a small, coastal stream. The majority of the population was static and resided within a home range < 22 m2, while a small fraction of the fish apparently was more mobile. Local movement was very restricted; 32.4% of the individually marked cutthroat were recaptured within 1 m of their original capture and marking site, and 48% remained within 3 m of that site. Only 17.9% of the fish moved more than 50 m. This behaviour was stable during winter, spring, and summer and may be of adaptive significance. Fish occupying pool areas moved considerably less than fish occupying shallow habitats, indicating that pool dwellers were dominant fish.