Changes in yellow perch (Perca flavescens) growth associated with the establishment of a walleye (Stizostedion vitreum) population in Canadarago Lake, New York (USA)

Piscivorous fish can affect prey growth in two ways: directly by reducing p rey density and indirectly by inducing predator-avoidance behaviors. We inv estigated these two pathways in yellow perch (Perca flavescens) growth resp onses to walleye (Stizostedion vitreum) stocking in Canadarago Lake, New Yo rk (USA) using a 25-year time series. Before walleye stocking, yellow perch growth rate was low and independent of body size. As walleye abundance inc reased, yellow perch growth increased and became size-dependent. The switch to size-dependent growth occurred in 1 year, indicating a rapid behavioral response to predators. Mean growth rate increased more gradually and was l inearly related to walleye density, indicating a slower numerical effect of walleye on yellow perch densities. Although the net effect was an increase in perch growth, small perch growth initially decreased as walleye became established. Therefore, the combination of numerical and behavioral effects produced a complex pattern of size-dependent changes in growth of yellow p erch.