Predation-Induced Differences in Growth and Reproduction of Bluegills (Lepomis macrochirus)

We compared growth and reproduction of bluegills (Lepomis macrochirus) in a reservoir where fishing was not allowed (Par Pond, South Carolina) to reservoirs that are fished. Because of intense fishing pressure, public reservoirs have relatively low abundance and small size-structure of natural predators (e.g., largemouth bass). Largemouth bass (Micropterus salmoides) in Par Pond were 3-4 times more abundant and 10-30% larger than bass in other reservoirs in the southeastern United States. Bluegills in Par Pond grew faster and attained larger adult sizes than bluegills in other populations. Par Pond bluegills were about two years older and 80 mm longer at maturity than bluegills in other southeastern United States reservoirs. Bluegills in Par Pond began reproduction at about the same size that they outgrew the threat of predation (about 190 mm total length). Differences in bluegill growth and reproduction appeared largely attributable to differences in abundance and size structure of predators in these reservoirs. Effects of high levels of predation on growth rates and reproduction of bluegills in this study were different from the effects of predation at low levels as studied in other systems.