Net Contribution of Fingerling Stocking to Walleye Abundance in Northern Wisconsin Lakes

The contribution of stocking to sport fish populations is typically assessed by estimating survival rates of stocked fish or estimating the proportion of stocked fish in indices of abundance or biomass. However, these evaluations only evaluate potential positive effects and do not consider the overall net contribution of stocking (i.e., potential positive and negative effects). To determine the net contribution of fingerling stockings to walleye Sander vitreus populations in northern Wisconsin lakes, we partitioned total age-0 walleye catch rates into proportions of stocked and naturally-produced walleye and compared between stocked and unstocked lakes during 2000-2014. Catch rates of all age-0 walleye did not differ between stocked (28.8/mile) and unstocked lakes (27.5/mile; F_1,232 = 2.04; P = 0.16), but catch rates of naturally-produced age-0 walleye in stocked lakes (12.6/mile) were significantly lower than catch rates in unstocked lakes (27.5/mile; F_1,232 = 27.93; P < 0.01). Although stocking may increase abundance of year classes in lakes with no or minimal natural reproduction and recruitment, preliminary results suggest that in lakes with both naturally-produced and stocked walleye, naturally-produced walleye may be replaced with stocked fish, with no net increase in overall abundance.