An experimental study of the effects of smallmouth bass on the behavior, growth and survival of prey fish

ABSTRACT The effects of smallmouth bass on the behavior, growth and survival of the prey fish (goldfish, ayu and Japanese dace) were examined experimentally in artificial ponds. In most cases, goldfish aggregated both when smallmouth bass were present and absent. Ayu and Japanese dace aggregated more frequently in the presence of smallmouth bass. All prey fish fed predominantly on benthic algae or aquatic insects and their dietary composition was not affected by smallmouth bass. In goldfish and Japanese dace, the total number of feeding acts exhibited by each individual was significantly less in the presence of smallmouth bass than in the absence and, in goldfish, the growth rate was less when smallmouth bass were present. In contrast, the presence of smallmouth bass did not affect either the total number of feeding acts or the growth rate of ayu. However, ayu were preyed on by smallmouth bass most frequently among the three prey species. Smallmouth bass tended to prey on smaller individuals, but ayu were not smaller than goldfish or Japanese dace.