Range-Wide Model Predictions of the Effect of Walleye Regulations on Yield, Catch-at-Age, and Population Structure

Regional fishing regulations play important role in the control and sustainable management of fish population. On the other hand, it is important to understand the effect that a given fishing regulation has on catch and population structure. This quantitative understanding is particularly important when the number of populations in a region exceeds the capacity to monitor and manage on an individual basis. Conventional approaches to estimating these effects (e.g., surplus production, stock-recruitment) assume that population regulation occurs via density-dependent changes in net productivity, egg production, and/or survival early in life. However, these approaches ignore density-dependent changes in growth and maturity, which affect the dynamics of an exploited population in important ways. In this study, we present a general modeling framework developed for walleye (Sander vitreus) and compare existing and novel regulations in terms of their effects on catch and population structure. This compensation model uses degree-days and biphasic growth theory to convert density-dependent life history changes into population dynamics that vary with regulation and climate. We demonstrate how this model can be used to tailor regulations to desired fishery outcomes.