Potential competition among young-of-year fish in western Lake Erie

This study was undertaken to determine the extent to which competition among young-of-year fish affects year-class strength of common commercial, sport, and forage fish in western Lake Erie. To determine which fish species share food resources and, therefore, may be competing, stomach contents analyses were performed on young-of-year alewife (Alosa pseudoharengus), emerald shiner (Notropis atherinoides), spottail shiner (Notropis hudsonius), freshwater drum (Aplodinotus grunniens), rainbow smelt (Osmerus mordax), trout-perch (Percopsis omiscomaycus), white perch (Morone americana), white bass (Morone chrysops), yellow perch (Perca flavescens), and walleye (Stizostedion vitreum vitreum). Fish were collected from a nearshore site (near Bono, Ohio) and an offshore site (near Middle Sister Island) in 1983 and, in 1984, at Middle Sister only. The analyses of stomach contents revealed that among the fish species studied, white perch consistently had high diet overlaps with white bass and yellow perch. A comparison of fish diets among fish collected during 1983 and fish collected in 1958 by Price, showed that changes in Lake Erie due to eutrophication have affected fish diets between years.;To determine whether young-of-year fish were competing for scarce food resources in 1983 and 1984 near Middle Sister Island, the energy necessary for freshwater drum, white bass, white perch, and yellow perch to maintain themselves in the western basin (i.e., in situ maintenance requirement) was calculated using models for the metabolic costs of swimming and for excretion of ammonia that were developed in this study. Consumption and egestion, were calculated with models obtained from the literature. The results showed that, among these four fish species, white perch consistently had more net energy available for growth and other activity than the other fish species. Competition for scarce food resources was found more likely to have occurred during 1984, when fish abundances were high in western Lake Erie. Whether competition affects year-class strength could not be shown, but circumstantial evidence suggests that it may for some fish species, such as yellow perch, during years of high fish abundance.