Food and Feeding Preferences of Rainbow and Brown Trout in Southern Appalachian Streams

Abstract

The stomach contents of Age 1 and older rainbow (Salmo gairdnert) and brown trout (S. trutta) in five southern Appalachian soft-water streams were compared with concurrent drift samples. A wide range of food items was consumed, and no prey genus comprised an average of more than 2.5% by number of the diet of either trout species. Seasonal changes in composition of drift from June to November were generally mirrored by shifts in trout diets. The contribution of terrestrial organisms to drift and to diets was highest in late summer and autumn. Averaged over all sam- ples, terrestrial taxa comprised 36, 45 and 50% of the drift, rainbow and brown trout diets, respectively. Both trout species exhibited statistically significant feeding prefer- ences for particular taxa (notably terrestrial organisms), but most prey were con- sumed in proportions similar to their abundance in the drift. Opportunistic feeding lends stability to trout populations in streams with relatively low autochthonous food production by allowing trout to capitalize on terrestrial input. Our findings empha- size the importance of both protecting riparian vegetation (which is a source of terres- trial prey) and considering aquatic habitat elements in which trout can efficiently capture surface drift when determining minimum stream flow requirements for water-diversion projects.