Evaluation of a Management System for a Mixed Walleye Spearing and Angling Fishery in Northern Wisconsin

In response to Chippewa tribal harvest declarations, the state of Wisconsin lowers daily angling bag limits for walleye Stizostedion vitreum in an attempt to avoid a maximum adult walleye exploitation of 35% on more than 1 in 40 occasions. We asked whether uncertainty in estimates of total allowable catch (TAC) and the sliding bag limit system used to manage anglers allowed the state to meet the overharvest risk level. During 1990–1998, 20–25 lakes were randomly sampled each year to estimate adult walleye stock and walleye harvest by angling and spearing. Adult walleye exploitation was calculated as the sum of angling and spearing exploitation rates. Adult walleye exploitation rates averaged 11.83% and did not vary significantly among years during 1990–1998. Angling exploitation averaged 8.38%, and spearing exploitation averaged 3.45%. Out of 210 lakes sampled during 1990–1998, only 4 (1.9%) had total exploitation rates that exceeded 35%. Since the exploitation rates were measured with error, we used Monte Carlo simulations to determine how observation error affected the likelihood of exceeding 35% total exploitation. The probability of exceeding 35% exploitation was 2.87%, and only Monte Carlo simulations on lakes regulated as having two‐bag limits were under the 2.5% risk level. The development of a management system that incorporates angler response and uncertainty into the estimates of TAC should allow for total exploitation rates that do not exceed risk levels.