Evaluation of competition between age-0 yellow perch (Perca flavescens) and gizzard shad (Dorosoma cepedianum) in Oneida Lake, New York

Diet and growth of age-0 yellow perch (Perca flavescens) and age-0 gizzard shad (Dorosoma cepedianum) were compared during June-August 1990 and 1991. In both years, Daphnia dominated the zooplankton community in June and early July but disappeared in mid-July and early August. Age-0 yellow perch consumed primarily Daphnia and copepods until the Daphnia stocks were depleted then switched to benthic prey. Small age-0 gizzard shad primarily selected Daphnia and copepods while larger individuals consumed fewer zooplankton and more phytoplankton. Data from 1984 through 1993 indicated no direct effect of interspecific competition on growth rates of either species. The decrease in Daphnia populations in years with abundant age-0 gizzard shad occurs later in the year than in years with abundant age-0 yellow perch, and we suggest that this timing is crucial for the outcome of fish interactions. When Daphnia decline later in the season, larger age-0 yellow perch can switch to benthic prey and larger age-0 gizzard shad to phytoplankton; thus, the outcome of these interactions differs from the depression of age-0 bluegill (Lepomis macrochirus) by competition from age-0 shad reported from many reservoirs.