Effects of colonizing predators on yellow perch (Perca flavescens) populations in lakes recovering from acidification and metal stress
We examined the effects of predator species on yellow perch (Perca flavescens) from lakes in the Sudbury mining region (Ontario, Canada), where fish communities are just beginning to recover from the effects of decades of acidification and metal stress. The predation regimes investigated included six lakes with no predators, four lakes recently invaded (≤3 years) by predators, and eight lakes with well-established (≥15 years) predator populations. Netting survey results indicated that yellow perch biomass was 69% lower in lakes with predators. In lakes recently invaded by predators, perch displayed earlier ontogenetic diet shifts from zooplankton to benthos and much poorer growth during their first growing season. Energy investment (lipid content per egg) in eggs by mature females was also less in the lakes recently invaded by predators. Growth potential in adult perch (age 1), estimated by nucleoside diphosphokinase, was highest in lakes with established predators. Body condition, controlling for size of perch, was also greatest in established predator lakes. Perch body shape in lakes with predators showed a shift from a typical streamlined, pelagic body form towards a deeper-bodied benthic body form, a change that may increase foraging efficiency for benthos or represent an antipredator strategy.