Patterns of integration of invasive round goby (Neogobius melanostomus) into a nearshore freshwater food web

Understanding trophic interactions of non-native species is a key step in elucidating their ecological role in recently invaded systems. The benthic fish species round goby (Neogobius melanostomus) has successfully established in aquatic systems across the world, with abundances increasing dramatically over relatively short time periods. Though this (at times) voracious benthivore can become an increasingly important forage fish for piscivores, relatively little is known about how prey and production pathways that support round gobies vary in space and time. In 2010, we collected round gobies from ten nearshore sites, over three seasons, in Lake Michigan, U.S.A. Due to recent changes in Lake Michigan, the dynamic nearshore region may be crucial for stability of the whole-lake food web. We assessed the role of round gobies in the nearshore Lake Michigan food web using stomach contents, fatty acid profiles, and δ13C and δ15N stable isotopes. Patterns in all of these measures were highly influenced by site, suggesting that local conditions, such as substrate composition or proximity to riverine inputs, were important in structuring round goby trophic interactions. By contrast, season of sampling and depth of collection had relatively weak associations with observed patterns. Few broad, regional patterns were evident, including a relatively high reliance on benthic production pathways on the western side of Lake Michigan. The observed variety in feeding patterns of round gobies, including potential for exploitation of different production pathways, may contribute to long-term persistence of this aquatic invader in new habitats.