The influence of body size and season on the feeding ecology of three freshwater fishes with different diets in Lake Erie

Isotopic niche and length-isotope relationships were quantified across the body size of three similarly-sized fish species with different feeding strategies as adults (benthivore: freshwater drum, Aplodinotus grunniens; pisciyore: walleye, Sander vitreus; and omnivore: white perch, Morone americana) in Lake Erie's western basin using delta C-13, delta N-15 and delta S-34. Stable isotopes demonstrated that resource utilization changed with body size for all three species and length-isotope relationships varied with season. Isotopic niche overlap was lower when modelled with three isotopes (delta C-13, delta N-15, and delta S-34) than with two (delta C-13 and delta N-15), providing greater resolution of feeding ecology among the species. Based on isotopic niches, there was significant overlap in resource use among species and size classes in spring, but overlap decreased in the fall for both. In this study, freshwater fish species with different adult feeding strategies partition resources through different mechanisms that vary through body size and season. Isotopes supported the generally identified feeding ecology of each species but demonstrated that each species underwent significant changes in feeding ecology with increasing body size. Changes in isotopes across season, and body size for each species demonstrate the need for a more thorough understanding of how resource use changes with body size and season in freshwater fish. (C) 2019 International Association for Great Lakes Research. Published by Elsevier B.V. All rights reserved.