Trophic ecology of freshwater drum in large rivers

We compared growth and diets of freshwater drum (Aplodinotus grunniens) collected from the Ohio and Kanawha rivers to those reported in the literature for freshwater drum in lentic systems. Diets of freshwater drum in large rivers were primarily composed of detritivores such as molluscs, crayfish and collector-gatherer invertebrates (trichopterans, ephemeropterans and dipterans) whereas zooplankton (cladoceran) and dipteran prey dominated freshwater drum collected from lakes and reservoirs. These differences were predicted by differences in energy pathways between lentic (plankton-based) and lotic (detrital-based) systems. Growth of freshwater drum was significantly higher in lotic (N=4) than in lentic (N=8) systems. Data from the Ohio and Kanawha Rivers reveal longer annual feeding cycles and greater growth in large rivers than in lentic waters. This differential growth may be caused by differences in forage base and temperature.