Evaluation of a Modified Bag Limit for Walleyes in Wisconsin: Effects of Decreased Angler Effort and Lake Selection

Abstract

We evaluated a modified daily bag limit for walleyes Sander vitreus to determine whether management goals were achieved. The modified bag limit consisted of no minimum length limit but allowed a daily harvest of only one walleye longer than 356 mm. The Wisconsin Department of Natural Resources implemented the single-fish, 356-mm regulation in 1997 on a number of lakes in northern Wisconsin that were previously subject to a 381-mm minimum length limit. The intent of the regulation was to increase the harvest of smaller walleyes in order to increase growth, spawning stock abundance, and harvest rate in lakes characterized by high densities of slow-growing walleyes. We examined the effects of the regulation in light of variables associated with walleye populations, the walleye fishery, and tribal harvest. All lakes included in our evaluation are located within the ceded territory of northern Wisconsin, where tribal harvest of walleyes, which is regulated differently than angler harvest, occurs annually. The daily bag limit for walleyes ranged between two and five, depending on the level of tribal harvest. Walleye fishery characteristics measured before 1997 (381-mm limit) and after 1999 (single-fish, 356-mm limit) demonstrated an increased angler harvest rate and a decreased mean length of harvested walleyes. However, we found none of the desired changes in walleye population characteristics. In addition, we found no evidence that lakes that were changed to the single-fish, 356-mm regulation were characterized by slower growth than those that retained the 381-mm regulation. The single-fish, 356-mm regulation requires increased harvest to achieve the desired changes to walleye population characteristics. Our results suggest that a significant decline in angler effort over time, in conjunction with the possibility that the lakes selected to receive the single-fish, 356-mm regulation did not exhibit particularly slow walleye growth, acted to offset increases in harvest rate and played a role in the general failure of this regulation to meet its goals.