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Winter stream conditions at elevations between 2,280 and 3,205 m above mean sea level and the use of winter habitat by adult brook trout Salvelinus fontinalis above 2,990 m were evaluated in 1983–1984 and 1984–1985. Little surface ice was observed at elevations above 2,900 m, which was associated with high snow accumulation; moderate surface ice and anchor ice formation were observed at elevations from 2,550 to 2,900 m; extensive surface ice formation occurred at 2,550 m. Little snow accumulated at 2,550 m and surface ice physically excluded substantial brook trout habitat. In late fall, brook trout at elevations above 2,990 m tended to move into low‐gradient areas where they remained active throughout the winter. During winter, brook trout appeared to select for areas with maximum velocities of 15 cm/s or less, measured during summer low flow, and for deeper water, but not for substrate type.

Evidence that drainage basin morphology and trout standing stock are related through a functional link between geomorphic features and stream habitat quality is presented. Numerous significant univariate correlations were found between geomorphic variables, stream habitat variables, and trout standing stock in both high‐elevation forest and low‐elevation rangeland streams. Canonical correlations between geomorphic variables and stream habitat variables provided insight into the form of the functional link. Multiple‐regression equations predicting trout standing stock were dominated by geomorphic variables. When geomorphic variables alone were incorporated into regression models they predicted trout standing stock as accurately as did stream habitat variables.

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The habitat suitability index (HSI) model for brown trout Salmo trutta in stream systems, developed by the U.S. Fish and Wildlife Service, was tested with data from 30 reaches on nine streams in southeastern Wyoming. The HSI was not significantly correlated (P > 0.05) with brown trout standing stock. We analyzed 14 individual suitability index variables from the HSI model plus 25 other habitat variables for their relation to standing stock. Two HSI model variables and seven of the additional variables had significant correlations with brown trout standing stock. When these nine variables were used in multiple regression analysis, the best model (R2 = 0.52) for predicting standing stock (S, kg/hectare) of brown trout included measures of cover and flow regime: S = 1.71MTCR + 114.3 V14 ‐ 0.60; MTCR is a measure of cover availability and V14 is the average annual base flow expressed as a percent of average annual daily flow. An index of fishing pressure was also developed and found to significantly influence brown trout standing stock.

Cover is an important trout habitat component resulting from the geomorphologic characteristics of a stream channel, the stream‐bank interface with the riparian community, and the stream flow. By means of regression analysis, this study quantitatively describes the relative importance of three cover parameters (overhead bank cover, rubble‐boulder‐aquatic vegetation areas, and deepwater areas) and two cover models as indicators of trout standing stock in eight small streams in southeast Wyoming. Results indicated that overhead bank cover, provided primarily by riparian vegetation, is the cover parameter that explains the greatest amount of variation in trout population size.