Evaluation of a 15-Inch Minimum Length Limitfor Walleye Angling in Northern Wisconsin

Abstract

In 1990 the Wisconsin Department of Natural Resources implemented a 15-in (1 in = 2.56 cm) minimum length limit for walleyes Stizostedion vitreum on waters throughout the state, excluding some lakes where walleyes demonstrated slow growth or high mercury contamination. To determine if management goals for the regulation had been met, we examined the effects on lakes with self-sustaining walleye populations in the ceded territory of Wisconsin, specifically effects on population structure, exploitation, and angler catch and harvest. We compared creel survey data from up to 19 lakes sampled before and after the regulation had been implemented, including lakes affected by (N = 13) and exempted (N = 6) from the 15-in regulation. We also compared postregulation (1990–1998) creel and biological data from up to 76 lakes that were both affected and exempted. Effects of tribal harvest, which occurred on all of these 76 lakes but was not subject to the same length limit, were also examined using postregulation data. The length regulation reduced angler harvest and exploitation but did not affect catch rates, growth, or population structure. High levels of tribal harvest may have increased the total level of exploitation as expected, but few other effects were detected. Mean exploitation levels were relatively low during the study period and may account for the general lack of significant effects. The regulation seems to have provided walleye populations with some degree of protection from overharvest and overexploitation without producing unwanted consequences and probably contributed to the stability of the walleye fishery in northern Wisconsin.