Diet Patterns and Niche Overlap of Muskellunge and Co‐Occurring Piscivores in Minnesota Lakes

Abstract

AbstractMuskellunge Esox masquinongy, Northern Pike E. lucius, Walleye Sander vitreus, and Largemouth Bass Micropterus salmoides are popular sport fish that often co‐occur in aquatic systems. Although numerous studies have investigated interactions among these species, the simultaneous evaluation of diet patterns and niche overlap among all four species has not been conducted. Our experimental design aimed to quantify diet overlap among Muskellunge and the other piscivores, while lakes without Muskellunge were also sampled to compare the diets of the other piscivores in their presence or absence. Diets of piscivores from 10 Minnesota lakes were collected via gastric lavage and quantified using an index of relative importance. Diets of individual species were compared among seasons and predator length categories, and among‐species comparisons were also conducted by season and relative to Muskellunge presence using permutational multivariate ANOVA (PERMANOVA). Muskellunge consumed a wide range of prey, whereas Northern Pike and Walleye diets consisted primarily of Yellow Perch Perca flavescens and centrarchids. Largemouth Bass consumed more invertebrates, especially crayfish Faxonius spp. No species exhibited seasonal diet shifts, but diets were different among length categories for all species except Walleye. Although nonmetric multidimensional scaling ordinations indicated shared prey use, PERMANOVA results indicated that the diets of Muskellunge and Largemouth Bass were most different from each other and the other piscivores' diets across all seasons. Conversely, Northern Pike and Walleye diets were similar regardless of season or Muskellunge presence. Finally, lake‐scale habitat variables were correlated with piscivore diets, and Yellow Perch abundance was correlated with Walleye diets. Our results indicate that while Muskellunge, Northern Pike, Walleye, and Largemouth Bass can coexist in a variety of lakes, populations of important prey and habitat variables should be examined before management actions (e.g., stocking) are implemented to ensure adequate prey availability and to ensure that competition among these piscivores is not increased to the detriment of existing fisheries.