Prey Size Selection of Largemouth Bass and Walleye in Northern Wisconsin Lakes
Henry Gray Fisheries and Aquatic Sciences
Maxwel Wilkinson (Not Pictured) Master of Natural Resources
Over the past two decades, some northern Wisconsin lakes have experienced declines in walleye abundance with concurrent increases in largemouth bass abundance. Shifts in predatory species dominance from walleye to largemouth bass could have important implications for prey fish abundance and size structure, but the top-down effects of shifting predator composition depend in part on whether bass and walleye fill the same predatory niche and consume the same sizes of prey. To help understand potential effects of shifts in predator dominance, we used diets of largemouth bass and walleye collected from five northern Wisconsin lakes during May-October, 2024 and 2025 to determine if: 1) sizes of predominant prey; and 2) predator-prey total length (TL; mm) relationships differed between bass and walleye. Bluegill and yellow perch were most prevalent among prey fishes observed in diets. Largemouth bass and walleye consumed similarly sized bluegill during spring and fall but in summer, bass consumed larger bluegill than walleye. Largemouth bass and walleye consumed similarly sized yellow perch during summer and fall but in spring, bass consumed larger perch than walleye. Prey fish TL generally increased with predator TL for both species; however, the difference in average prey lengths consumed between largemouth bass and walleye decreased as predator TL increased. Although diet overlap between largemouth bass and walleye is relatively high, differences in the sizes of prey consumed suggest they may not fill the same predatory niche and could result in differences in prey fish population size structure.
Advisors: Daniel Dembkowski, Ph.D. Daniel Isermann, Ph.D.
Subject Area: Fisheries and Water
Type: Poster
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UW-Stevens Point College of Natural Resources
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