Food and Growth of the Freshwater Drum in Lewis and Clark Lake, South Dakota

Age 0 freshwater drum in Lewis and Clark Lake, a main stem Missouri River reservoir, consumed mostly zooplankton and chironomids, and age I and older fish consumed mostly Hexagenia. Zooplankton were important during the entire summer for age 0 fish, but were important only during the spring and fall for older fish. Bottom organisms were important food for age 0 fish longer than 40 mm and for age I and adults. A study of diurnal food habits revealed most zooplankton were consumed during daylight and most Hexagenia during darkness. Freshwater drum growth was poor during the first 6 years after impoundment (1956–1961), then improved between 1962 and 1966. Improved growth was related to an increase in Hexagenia abundance and was accompanied by an increase in freshwater drum density.