The spread of the invasive round goby (Apollonia melanostomus) in the Laurentian Great Lakes has been well documented, though their distribution in streams is less well known. During the summer of 2007 we sampled 73 distinct Wisconsin tributaries of Lake Michigan to determine the spatial extent of goby presence and associate their presence/absence with a suite of site and watershed scale variables. Our objective is to forecast the potential range of round goby and highlight sites at which prevention efforts would be the most beneficial.
Results/Conclusions  

Round goby presence was detected in 24 streams (33% of streams sampled), and was identified at sites >10km upstream of Lake Michigan in eight watersheds. We used multiple logistic regression to determine the habitat variables correlated with goby presence/absence and used a best subsets analysis to select the best model. The best model incorporated watershed area, slope, gradient, and conductivity and correctly predicted round goby presence/absence at 80 % of sampled sites. Based on this model, we identified sites suitable for round goby that have not yet been invaded. Our results provide empirical estimates for the range expansion of this non-native fish into Lake Michigan tributaries and suggest a need to further study the round goby in lotic systems.