Elucidating patterns of size-dependent predation on larval yellow perch (Perca flavescens) in Lake Michigan: an experimental and modeling approach

Abstract

Yellow perch (Perca flavescens) in Lake Michigan have experienced sustained recruitment failure since 1990 as a result of increased mortality during the pelagic larval phase. Increased mortality of larval yellow perch has been tied indirectly to increased alewife (Alosa pseudoharengus) predation, but effects of predation on larval survival variability must be better understood. We compared the relative importance of predation by alewife and two other fish predators to larval survival in laboratory experiments and developed an individual-based predation model (IBM) to examine patterns in size-dependent predation vulnerability. Simulations exposing larval perch to predation by all predators suggest that larval mortality resulting from alewife predation is more size-dependent than mortality resulting from the other two predators, and the range of sizes vulnerable to alewife is smaller. Alewife predation may not be an important mortality source for larval yellow perch in Lake Michigan at present because of the narrow range of vulnerable sizes and low densities of larval perch in the open lake. Predation is more likely to be important in smaller, more productive systems where other predators are abundant. Modeling results also indicate IBM analysis of date of hatch distributions of surviving larvae is a valuable tool for identifying factors most important to larval survival.