Forecasting the distribution of the invasive round goby (Neogobius melanostomus) in Wisconsin tributaries to Lake Michigan

The Laurentian Great Lakes host more than 180 non-native species, including several that have resulted in major economic and ecological effects. This list includes the round goby (Neogobius melanostomus), an aggressive, benthic Ponto-Caspian fish that has established large populations in coastal Great Lakes habitats. Here, we document the inland dispersal of round gobies into Wisconsin tributaries of Lake Michigan. Round gobies were detected in 26 of 73 streams (36%) and found >10 km upstream of Lake Michigan in nine watersheds. Round goby presence-absence was modeled using landscape-scale data from these invaded streams. We forecasted the future spread of round goby within Wisconsin's Lake Michigan basin using our best model (80% accuracy), which included watershed area, stream gradient, and watershed slope as predictors. Round gobies were predicted to invade 1369 kin of stream habitat up to the first stream barrier, and 8878 km of stream was identified as suitable looking beyond barriers at the broader Lake Michigan watershed (Wisconsin only). Our results depict the Great Lakes as a springboard for invasive species to disperse into inland ecosystems and, because round gobies are not usually reported in small streams in their native range, emphasize the utility of data from invaded regions when forecasting invasive species distributions.