Sex, Walleyes, and Slot Limits: Examining the Effects of Slot Length Limits on Walleye Population Demographics

Protected slot length limits (i.e., fish falling within a defined range of lengths cannot be harvested) have become a common tool for regulating harvest in walleye fisheries. These regulations typically allow harvest of smaller walleyes (e.g., < 17 or 18 inches total length) and then protect fish from harvest until they have attained lengths of 20 inches or more, where harvest is often regulated by a daily bag limit of 1 fish. Due to sexually dimorphic growth, these regulations should result in male fish being exposed to exploitation for a longer duration than females, because female fish attain the lower end of the protected length range sooner than males and harvest above the upper length boundary of the protected range is often low. Our objective is to determine if protected slot length limits have the potential to alter population dynamics and demographics in walleye populations. Sex-specific von Bertalanffy growth models from multiple lakes indicate that males are exposed to exploitation longer than females before attaining the lower end of a protected slot; however differences in exposure varied among lakes and were less apparent in fast-growing walleye populations. Results of modeling simulations and trends in walleye population demographics after implementation of slot length limits will be presented.