AUTHORS: Jeston Hassler, South Dakota State University; Maxwel Wilkinson, University of Wisconsin-Stevens Point; Quinnlan Smith, University of Wisconsin-Madison Center for Limnology; Joseph Mrnak, Wisconsin Department of Natural Resources-Escanaba Lake Research Station/University of Wisconsin-Madison Center for Limnology
ABSTRACT: In recent decades, some lakes in the Ceded Territory of Wisconsin (approximate northern third of the state) have experienced increasing largemouth bass Micropterus salmoides abundance coupled with declining walleye Sander vitreus abundance. These shifts in abundance have become of management concern, as largemouth bass have been hypothesized to negatively influence walleye populations through potential competitive or predatory interactions. Yet, a mechanistic understanding of these ecological interactions remains relatively unknown. As climate change continues to alter thermal habitat in northern Wisconsin lakes, understanding how warming water temperatures may influence largemouth bass and walleye interactions, specifically their consumption rates of prey items, could assist in the future management of the two species. Thus, our objectives in this study were to 1) calculate diet overlap and consumption rates of common prey items for largemouth bass and walleye in a northern Wisconsin lake and 2) simulate consumption rates of largemouth bass and walleye in predicted climate change scenarios. Our study site, Little John Lake located in Vilas Co., Wisconsin, contains a naturally recruiting walleye population and fish assemblage similar to many other northern Wisconsin lakes. We intensively sampled diets of largemouth bass and walleye in Little John Lake from May-October in 2024 and took a bioenergetics approach to estimate and simulate consumption rates of these species under climate-change scenarios. Increased rates of consumption were apparent for both species, notably of yellow perch Perca flavescens and Lepomis spp., yet walleye consumption rates slowed when water temperature began reaching their thermal tolerance. Understanding how largemouth bass and walleye consumption rates may differ under climate-change scenarios may give valuable insight into future interactions between these species in northern Wisconsin lakes.
