The Relationship between Age-0 Walleye Density and Adult Year-Class Strength across Northern Wisconsin

Walleyes Sander vitreus are an important cultural and economic resource in northern Wisconsin, both as a recreational fishery and a tribal subsistence fishery. Understanding the recruitment of age-0 walleyes to the adult population could be of great utility in effectively managing harvest and informing stocking efforts in this mixed-use fishery. Our objective was to determine the relationship between abundance of age-0 walleyes in the fall and the subsequent adult year-class 4 years later and to explain additional residual variation related to environmental variables. Since 1986, fall electrofishing surveys have been conducted to estimate the densities of age-0 walleyes and spring mark–recapture surveys to estimate spawning adult walleyes. We fit a gamma stock–recruitment curve to a data set of 104 paired surveys (age-0 survey with adult survey conducted 4 years later) on 58 lakes and attempted to explain residual variation related to additional environmental variables. Our analysis suggests that the maximum number of age-4 fish (3.36/ha) is not produced by the maximum number of age-0 fish but by a somewhat intermediate density (243/ha) and that this relationship varies with the complexity of the shoreline. This density-dependent relationship should help managers refine models forecasting walleye abundance, as well as optimize stocking rates. Received December 28, 2011; accepted April 27, 2012