Body Conditions and Stomach Contents of Subadult Trout during Fall and Winter in Three Wyoming Tailwaters

Abstract

We studied three tailwaters in Wyoming from October 1997 through February 1998 to determine whether body conditions of stocked, subadult rainbow trout Oncorhynchus mykiss or cutthroat trout O. clarki declined from fall through winter and to assess whether lack of food in stomachs might be related to any declines. Body conditions of rainbow trout in two tailwaters remained high through the winter. Body conditions of cutthroat trout in a third tailwater declined between October and February but not to levels anticipated to affect the overwinter survival of the fish. Trout with substantial amounts of food in their stomachs were found throughout the fall and winter in all three tailwaters. In no subadult trout in any of the three tailwaters did we observe rapid declines in body conditions during fall or continuous declines in body conditions to very low levels by the end of winter in association with low biomass of food in stomachs.