Food and Distribution of Underyearling Brook and Rainbow Trout in Castle Lake, California

Abstract

Abstract A difference was found in the summer distribution of underyearling brook trout, Salvelinus fontinalis (Mitchill), and planted rainbow trout, Salmo gairdneri Richardson, in Castle Lake, California. Brook trout underyearlings oriented to the bottom and were found primarily in shallow water on the eastern shore of the lake near springs. The rainbow trout underyearlings were more pelagic and were found in the littoral areas along the entire shoreline. Gravimetrically, the food eaten during the summer by brook trout underyearlings was 13% terrestrial, 11% limnetic, and 76% benthic. Rainbow trout ate 15% terrestrial, 15% limnetic, and 70% benthic food. In summer, rainbow trout adults are located in the epilimnion in Castle Lake, whereas adult brook trout are found near the bottom of the lake beyond the littoral zone. Due to this spatial isolation, their diets differ considerably. An earlier study showed that during the summer, adult brook trout ate 20% terrestrial, 31% limnetic, and 49% benthic food (b...