The effects of Bythotrephes longimanus invasion on diets and growth of age-0 yellow perch in Oneida Lake, New York

Bythotrephes longimanus is a predatory zooplankton native to Eurasia known for its large caudal spine. This species can decrease Daphnia abundance and may decrease growth rates of native planktivorous fish including yellow perch (Perca flavescens). Bythotrephes was first documented in Oneida Lake, USA in 2019 and reached high densities in 2020 and 2021. This recent invasion created an opportunity to investigate at what length yellow perch feed on Bythotrephes, if age-0 yellow perch select for Bythotrephes, and if yellow perch first-year growth decreased. We found Bythotrephes in the stomachs of 23% (2020) and 35% (2021) of age-1 and older yellow perch caught from June through September and 54% of the age-0 yellow perch caught from June through October (2021). Age-0 yellow perch started feeding on Bythotrephes at 27 mm and selected for Bythotrephes from June 24 through the autumn of 2021. Bythotrephes accounted for 54% of age-0 diets by dry weight over the summer and fall. We used the extensive water quality and biological monitoring data from Oneida Lake to develop a multivariate linear regression model for age-0 yellow perch October length from 1993 to 2021. Significant variables included were age-0 yellow perch abundance (negative effect) and temperature, Daphnia biomass, and Bythotrephes presence, all positive effects. Contrary to our expectations, Bythotrephes were selected by age-0 yellow perch from end of June through October, and contributed a substantial proportion of ingested mass by age-0 perch, without negatively affecting age-0 yellow perch growth.