Absence of Autumnal Changes in Habitat Use and Location of Adult Colorado River Cutthroat Trout in a Small Stream

Previous research has demonstrated that stream salmonids typically alter their behavior and habitat use with the onset of winter. Using radiotelemetry, I monitored the activity, habitat use, and location of Colorado River cutthroat trout Oncorhynchus clarki pleuriticus in a small stream in south-central Wyoming from early July to late October. Summer (July through August) home ranges did not differ in size (32 m) or location from autumn (September through October) home ranges (38 m). Habitat use also remained constant in both seasons; trout were in pools for over 70% of the observations. However, daytime trout activity declined from 98% of observations in July and August to 48% in October. The lack of movement and failure to change habitat use may be attributable to the wide availability of suitable substrate for concealment and likely year-round low water temperatures.