Simulated dispersal of exotic rainbow smelt (Osmerus mordax) in a northernWisconsin 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 th rough stream connections among lakes and watersheds, and survival based on physical and chemical factors of lakes within a northern Wisconsin watershe d. One fourth of the habitable lakes contained rainbow smelt after 1000 yea rs if dispersal was restricted to stream corridors. In contrast, with prese nt rates of human transport, half contained rainbow smelt after 200 years, three quarters after 300 years, and all after 1000 years. Simulated human i ntroductions increased the number of epicenters for spread and were the mos t influential parameter in the model. Stream connections between lakes incr eased 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 highlig ht the importance of human vectors in driving exotic fish dispersal, sugges t that isolated lakes are important refuges for species negatively affected by rainbow smelt, and show that agencies interested in controlling the spr ead of exotic fishes need to strongly consider the human vector of transpor t.