Monitoring round goby (Neogobius melanostomus) population expansion in eastern and northern Lake Michigan

In the Great Lakes basin, round gobies (Neogobius melanostomus) were first reported from the St. Clair River in 1990. Reported here are the details of range extension and establishment of round gobies in eastern Lake Michigan at Grand Haven, Michigan and in northern Green Bay, at Escanaba, Michigan. Round gobies were first collected in survey, samples at Grand Haven in 1997 (0.0 to 0.5 fish per trawl hour). Catch rates increased in 1998 (1.5 to 3.0 fish/h) and 1999 (38.0 to 69.0 fish/h). Individuals collected by, trawling (N = 207) ranged in total length from 18 to 94 mm. Round gobies were first collected in survey (trawl) samples at Escanaba in 1998 (7.5 fish/h; total length range 43 to 58 mm). Round gobies were also collected during 1999 in trawls at Muskegon and in gill nets at Grand Haven and Saugatuck. No round gobies were collected at five other eastern Lake Michigan ports sampled during this same time period (1995 to 1999). Numerous adult round gobies were captured by, anglers at Grand Haven and Escanaba, indicating that these populations had been established for some time prior to being detected in survey sampling. Additional populations were verified from angler reports at Charlevoix (1998) and Kipling (1999), Michigan. Round gobies collected by anglers were generally larger, and taken in areas that are difficult to sample using conventional inshore sampling gear. These results indicate that survey and angler samples are complementary, but that up-to-date angler reports of exotic species that bite readily (round gobies) or are otherwise collected by anglers (Bythotrephes cederstroemi, Cercopagis pengoi) are critical to tracking the spread of these organisms.