Ecological responses to elevated water temperatures across invasive populations of the round goby (Neogobius melanostomus) in the Great Lakes basin

Climate warming is expected to alter the distribution, abundance, and impact of non- native species in aquatic ecosystems. In laboratory experiments, we measured the maximum feeding rate and critical thermal maximum (CTmax) of an invasive Eurasian fish, the round goby (Neogobius melanostomus), acclimated to a range of temperatures (18-28 degrees C) reflecting current and projected future thermal conditions for the nearshore Great Lakes. Fish were collected from four distinct populations along a latitudinal gradient from the western basin of Lake Erie to Hamilton Harbour (Lake Ontario) and the upper St. Lawrence River. Thermal tolerance increased with acclimation temperature for populations in Lakes Erie and Ontario. However, the St. Lawrence River populations had lower acclimation capacity and exhibited an unexpected decline in CTmax at the highest acclimation temperature. Maximum feeding rates peaked at 18-24 degrees C and declined with temperatures above 24 degrees C. Northern populations in the basin appear poorly adapted to elevated temperatures such that their performance and impact could be reduced by climate warming. Thermal response data from latitudinally distributed populations are needed to inform invasive species risk assessment.