Effects of Predation and Environment on Quality of Yellow Perch and Bluegill Populations in Nebraska Sandhill Lakes

We investigated factors that may influence the quality (e.g., high abundance, size structure, condition, and growth) of yellow perch Perca flavescens and bluegill Lepomis macrochirus populations in Nebraska sandhill lakes. Physical (e.g., lake depth, vegetation coverage), chemical (e.g., alkalinity, conductivity), and biological (e.g., chlorophyll a, invertebrate abundance) characteristics of 30 natural lakes were determined in 1998 and 1999. Growth, condition, and size structure were not density-dependent for bluegills or yellow perch in these shallow (,4mmaximum depth) lakes. However, bluegill abundance, size structure, and condition were positively related to yellow perch abundance, size structure, and condition. Bluegill quality tended to increase with increased emergent vegetation, whereas yellow perch quality was not correlated with any physicochemical variable measured. Submergent vegetation coverage ranged from 5% to 97% of lake surface area and was not related to panfish quality. The mean relative weight (Wr) of larger (15– 20 cm) bluegills was positively associated with high Daphnia and Cyclops abundance, whereas the mean Wr of 20–25-cm yellow perch was not related to invertebrate abundance. Higher relative abundance and lower proportional stock density of largemouth bass Micropterus salmoides were positively related to panfish quality, even in lakes up to 341 ha. Quality panfish populations in the Nebraska sandhills are influenced by predators, prey, and the environment. However, based on the high correlation coefficients, largemouth bass may be most influential in structuring the quality of bluegill and yellow perch populations in these shallow natural lakes