Abiotic and Biotic Factors Influencing Largemouth Bass Growth in Wisconsin

Abstract

Fish growth can be highly variable among populations of the same species due to differences in abundance, system productivity and watershed characteristics. Because of this, understanding factors that influence fish growth and body condition is important to managers for fish conservation, to meet angler desires and to support local economies. As ecosystems respond to a changing climate, species compositions can change. In north temperate lakes, this is often exemplified by an increase in largemouth bass (LMB). These lakes are often managed for multiple fish species concurrently, making standardized fishery-independent LMB data limited, creating challenges for managing this species. As such, a better understanding of factors influencing LMB body condition and growth may become critically important in the future. We assessed LMB age, length, and weight data to test for abiotic and biotic lake characteristics explaining variation in LMB body condition, asymptotic length, and mean length at age metrics in Wisconsin from 1994 to 2022. Macrophyte species composition and lake classification relationships were the two primary predictors of variation in LMB growth. Lakes with degraded macrophyte communities were associated with larger individual LMB sizes as were lake class types that contained cool water and riverine characteristics. Our results provide fisheries managers with options when dealing with diverse angler desires and a heterogenous landscape of lakes. Where available, macrophyte species composition data can be consulted by managers to identify opportunities to provide a trophy fishing experience in a system that otherwise would be undervalued. As populations of LMB increase in Wisconsin lakes, a better understanding of how to effectively reach goals set by managers, and what realistic goals might be, is required, and understanding what lake characteristics can explain variation of body condition gives insight to that end.