2012): Impacts of the Eurasian round goby (Neogobius melanostomus) on benthic communities

Abstract: An invasive benthivorous fish, the Eurasian round goby (Neogobius melanostomus) is abundant throughout the lower Great Lakes – St. Lawrence River system. We examined the round goby’s potential to alter benthic communities on cobble substrates in the upper St. Lawrence River. During the summers of 2008 and 2009, macroinvertebrates and benthic algae were sampled across sites with varying goby densities. Archived data from various sites in 2004–2006 (prior to inva-sion) were available for comparison. Macroinvertebrate community composition varied significantly among samples grouped into categories based on goby density and time since invasion. Macroinvertebrate diversity and dominance by large-bodied taxa declined with increasing goby density. Surprisingly, dreissenid biomass did not vary consistently with goby density, in contrast to studies in the Great Lakes. The biomass of all non-dreissenid taxa was negatively correlated with increasing goby density across sites and over time at three of four sites. Negative effects were most pronounced on the biomass of gas-tropods. Benthic algal biomass increased with goby density across sites, suggesting a trophic cascade driven by the impacts of gobies on gastropods and other algivores. Our study highlights the potential ecosystem impacts of an expanding goby population in a large river. Résumé: Le poisson envahissant, consommateur de benthos, le gobie à taches noires d’Eurasie, Neogobius melanostomus, est abondant dans l’ensemble du système des Grands Lacs inférieurs et du Saint-Laurent. Nous étudions le potentiel qu’a l