Seasonal variation in dietary overlap between yellow perch ( <i>Perca flavescens</i> ) and bluegill ( <i>Lepomis macrochirus</i> ) in backwater lakes of a large river

When large river ecosystems exhibit shifting habitat mosaics and fish community composition, understanding spatial-temporal dietary patterns may inform season-specific dietary overlap between species. Backwater areas of the Mississippi River exhibited an ecological shift to a macrophyte-dominated clear water state with an associated increase in yellow perch (Perca flavescens) abundance from 2005 to 2010. This exploratory study assessed diet patterns and overlap between the more newly abundant yellow perch and previously established bluegill (Lepomis macrochirus). We examined the gut content of both species in three backwater contiguous lakes of Mississippi River Lower Pool 4. We removed stomach content of bluegill (n = 61) and yellow perch (n = 189) from May 2018 through January 2019 and categorized stomach content remains to the lowest identifiable taxonomic level. Bluegill and yellow perch exhibited overlapping generalized feeding strategies during spring, summer, and fall and non-overlapping specialized feeding strategies during winter. Yellow perch diets in the winter were significantly different from all other seasons (all pairwise ANOSIM p < 0.05, R statistic > 0.36). In winter, 99.7% of prey fish volume in yellow perch occurred in large-size-class fish. During the winter, age-0 bluegill made up 97% (by volume) of the prey fish found in large-size-class yellow perch. Yellow perch and bluegill diets overlapped the least in winter (ANOSIM p < 0.05; Schoener’s Index = 0.10) and the most in spring and fall (ANOSIM p > 0.05; Schoener’s index = 0.41 and 0.50), respectively. Overall, dietary overlap between yellow perch and bluegill varies seasonally. Due to the limited sample size of this study, follow-up research is needed to further assess seasonal and size-dependent patterns and to assess if competition and or predation from the newly abundant yellow perch population is affecting bluegill abundance, recruitment and growth.