Trends in body condition of native piscivores following invasion of <scp>L</scp>akes <scp>E</scp>rie and <scp>O</scp>ntario by the round goby

Abstract

Summary Biological invaders can provide a highly abundant novel prey, yet the effect this has on the body condition of native predators is unknown. Since invading the L aurentian G reat L akes over two decades ago, the round goby ( N eogobius melanostomus ) has become an important food source for many native species. We used long‐term data from L akes E rie and O ntario (1993−2012) to create quantile regression models of mass–length relationships for populations of four native predators: smallmouth bass ( M icropterus dolomieu ), yellow perch ( P erca flavescens ), walleye ( S ander vitreus ) and burbot ( L ota lota ). Model‐based estimates of changes in mass‐at‐length following the invasion were used to compare the effects of round goby on relative trends in body condition. Water temperature data were also included in the models, to investigate its effects on body condition. The condition of smallmouth bass increased after the invasion, varying in magnitude between lakes and among size classes. Condition of yellow perch changed variably in direction and magnitude, depending on the quantile of the mass–length relationship examined and fish length, whereas that of walleye increased only for larger fish in L ake O ntario. Minor increases in mass‐at‐length were observed for the smallest length class of burbot, while the body condition of burbot in the largest length class decreased during the study period. Mean summer water temperature did not differ between pre‐ and post‐invasion time periods in L akes E rie and O ntario, although water temperature was a significant predictor of body condition. Changes in body condition may have implications for additional population and life history characteristics. Future research should investigate the effects of the round goby on growth, age at maturity, fecundity and survival of native predators.