The recent establishment of the round goby (Neogobius melanostomus), an invasive fish in Lake Michigan, provides a model system to view fine scale evolutionary and ecological processes that can create genetic structure within a population. We used seven nuclear polymorphic microsatellite markers (N = 11-17 per site) and measurements of fish total length, weight, and sex (N = 20-74 per site) on round gobies captured by minnow traps and angling among 12 sites around the entire shore of Lake Michigan to determine if evolutionary processes are present in Lake Michigan by characterizing population structure of the round goby. Specific objectives were to determine whether: 1) there are significant patterns of genetic population structure among sites along the shore of Lake Michigan (e.g., a correlation between genetic diversity and geographic distance), 2) ferry shipping routes create strong deviations from normal population structure observed to occur around the lakeshore, and 3) density, fish size, and condition at the 12 sites differ from each other. Results include: significant pairwise FST values, a pattern of isolation by distance (IBD) along the eastern and western shores of Lake Michigan, no IBD along the entire lakeshore, northern, or southern shores, different catch per unit effort (CPUE) and mean weight between sites. A length/weight relationship between fish at all 12 sites was not different. Results indicate that round goby pierhead sites exhibit population structure in Lake Michigan
