Simulated dispersal of exotic rainbow smelt (Osmerus mordax) in a northern Wisconsin lake district and implications for management

We simulated geographic dispersal of exotic rainbow smelt (Osmerus mordax) as a function of present introduction rates, the probability of invasion through stream connections among lakes and watersheds, and survival based on physical and chemical factors of lakes within a northern Wisconsin watershed. One fourth of the habitable lakes contained rainbow smelt after 1000 years if dispersal was restricted to stream corridors. In contrast, with present rates of human transport, half contained rainbow smelt after 200 years, three quarters after 300 years, and all after 1000 years. Simulated human introductions increased the number of epicenters for spread and were the most influential parameter in the model. Stream connections between lakes increased the number of lakes colonized; decreases in migration ability led to fewer invaded lakes. Although extinction was operating, human introductions outweighed extinction and led to a saturation of rainbow smelt across all habitable lakes within the watershed within 1000 years. Our results highlight the importance of human vectors in driving exotic fish dispersal, suggest that isolated lakes are important refuges for species negatively affected by rainbow smelt, and show that agencies interested in controlling the spread of exotic fishes need to strongly consider the human vector of transport.