The depth distribution of four fishes was studied using specially constructed vertical gill nets on Horsetooth Reservoir, Colorado (1960‐61). Of several environmental factors measured, water temperature was the one factor that exerted a measurable effect. Depth of capture increased for the rainbow trout, kokanee salmon, and white sucker as each summer progressed and in general followed the isotherms. The distribution of yellow perch was unaffected by temperature changes. Kokanee salmon were most abundant in waters of 51‐55° F. while the rainbow trout and white suckers were most numerous in 66‐70° F. waters.

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No conclusive evidence was found in tests from 1966 to 1969 in either lentic or lotic environments to support the hypothesis that hatchery-reared rainbow trout (Salmo gairdneri) with a high-stamina index had a higher survival potential than those whose stamina index was low. Physical stamina was measured by determining the length of time each fish could withstand sustained swimming in a specially constructed stamina tunnel. For high-stamina rating, fish swam in the tunnel for 80 min; for low stamina, 1–10 min.In tests of reproducibility of stamina ratings, improved swimming ability of low-stamina fish was demonstrated upon retesting in the tunnel. In 1970, with retested fish, still no evidence was found to indicate higher survival of fish rated as high in stamina. Additional studies are needed to determine if performance of hatchery-reared salmonids in a stamina tunnel is a valid indicator of their survival potential in the wild.