Early life dynamics of walleyes (Sander vitreus) in a Great Lakes tributary

Walleyes are dominant predators in Great Lakes ecosystems but have poor reproductive success. From 2009-2010, we studied factors influencing survival of walleye eggs and larvae in the Muskegon River tributary to Lake Michigan. We estimated egg densities from furnace-filter traps placed in shoreline areas. We estimated egg survival from changes in egg density over time in covered incubator chambers. We estimated densities of rusty crayfish, a potential egg predator, and conducted experiments in in-situ open and exclosure cages to determine the effect of crayfish predation on walleye egg survival.  We estimated larvae densities and production from drift nets set at night at fixed river sites. Walleyes spawned in early April, and peak egg densities  reached 86,000 eggs/m2.  Average survival of walleye eggs in incubator chambers was 45%, lower than survival (76%) under controlled hatchery conditions. Egg predation experiments showed no effect of rusty crayfish on walleye egg survival, and densities of crayfish were relatively low in walleye spawning areas.  Walleye fry drift from April to May was 4.5 ± 0.4 million, or 0.1% of egg production.  Average river temperatures during egg incubation were low (7°C) compared to optimal temperatures for walleye egg survival (9-15°C), suggesting temperature affected walleye reproductive success.