Factors limiting walleye reproduction in a Lake Michigan tributary

The Muskegon River historically supported one of the largest runs of adfluvial walleye in Lake Michigan.  Their number has declined since the 1950’s and today is largely supported by stocking efforts.  Our goal was to identify factors limiting walleye recruitment during early ontogeny at three sites in the river.  Mean egg densitiy was 6,894 eggs/m­­² (range=103-84,590 eggs/m²), and mean egg survival was 45% (range=21-70%) in incubators that excluded predators.  Our results suggest egg density and viability were not limiting factors when compared to similar systems with high natural reproduction.  Manipulative experiments (comparing open and exclosure cages stocked with known egg densities) showed that predation did not strongly affect egg densities.  However, drift sampling indicated a decrease in larval walleye abundance in downstream portions of the river.  The decrease in abundance may be associated with mortality caused by abiotic interactions or predation on larvae.