DETERMINANTS OF NESTING SUCCESS IN THE PUMPKINSEED (LEPOMIS-GIBBOSUS)- A COMPARISON OF 2 POPULATIONS UNDER DIFFERENT RISKS FROM PREDATION

We compared pumpkinseed nesting success in two lakes having similar si ze, location, and water chemistry but with different fish communities. Ranger Lake had well-established populations of smallmouth and largem outh bass and few planktivorous fish, whereas Mouse Lake had no pisciv ores and many planktivore-benthivores capable of consuming pumpkinseed eggs and larvae. Both lakes had well-established pumpkinseed populati ons, but nesting success was significantly higher in Ranger Lake. The influences of environmental factors (nesting substratum and depth, tem perature, solar radiation, precipitation, and wind velocity) on nestin g success were investigated, and only wind-induced water turbulence wa s important. Although wind events were associated with significant amo unts of nest destruction, the effects were the same in both lakes. Nes t attacks and male nest defense were higher in Mouse Lake, particularl y at night. These attacks came from the dense populations of golden sh iners found at Mouse Lake and resulted in the loss of many pumpkinseed nests. We conclude that a predator-induced cascade indirectly influen ced nesting success. At Mouse Lake, piscivores were rare, planktivore- benthivore nest predators were abundant, nest-specific behavioral inte ractions were numerous and nesting success was low. At Ranger Lake, la rge piscivores were abundant, planktivore-benthivore numbers were low, and nesting success was high.