Effects of Round Goby on the Benthic Invertebrate Community and on Diets and Growth of Yellow Perch and White Perch in Oneida Lake, New York

Food web changes from the introduction of nonnative species can be complex, with sometimes unexpected effects or little effect due to food web interactions. Invasive Round Goby Neogobius melanostomus became common in samples in Oneida Lake, New York, by 2014. Data from a long‐term monitoring program allowed us to document the Round Goby expansion through time. Using shoreline seine, fyke net, bottom trawl, and video surveys, we estimated that Round Goby density reached over 25,000 fish/ha 6 years after detection and subsequently varied between 4,110 and 26,565 fish/ha. Concurrent benthic invertebrate sampling and long‐term fish diet sampling allowed us to assess the impacts of Round Goby on densities of several benthic invertebrate taxa and on invertebrate consumption by fish. Significant decreases in density after Round Goby arrival were found for amphipods (Amphipoda), caddisflies (Trichoptera), snails (Gastropoda), and dreissenid mussels Dreissena spp. Invertebrate densities after Round Goby arrival ranged from 19% to 48% of densities in the pre‐Round Goby period. For amphipods, snails, and, in some cases, caddisflies and chironomids (Chironomidae), frequency of occurrence in the diets of Yellow Perch Perca flavescens and White Perch Morone americana was lower after Round Goby became established. The decreased consumption of these invertebrates did not lead to decreases in fish growth; growth increased for some age‐classes of Yellow Perch and all age‐classes of White Perch. Despite potential Round Goby predation, densities of burrowing mayflies Hexagenia spp. expanded during this time and likely helped to offset reductions in consumption of other invertebrates by Yellow Perch and White Perch, as did consumption of Round Goby. Long‐term monitoring shows that Round Goby decreased the density of several benthic invertebrate species and decreased the consumption of these invertebrates by fish, but the effect on growth of Yellow Perch and White Perch was offset by consumption of Round Goby and burrowing mayflies. Impact Statement Yellow Perch and White Perch are important sport fish and major players in freshwater food webs that may be affected by changes in benthic invertebrates and impacts from nonnative, introduced species. Changes can be complex with sometimes unexpected effects or little effect due to food web interactions. We used longterm data from Oneida Lake to show that the arrival of Round Goby caused substantial decreases in important benthic inv