Long-term impacts of invasive round goby Neogobius melanostomus on fish community diversity and diets in the St. Clair River, Michigan

This study examined long-term impacts of round gobies (Neogobius melanostomus) on native benthic fishes near Algonac State Park in the St. Clair River, Michigan. Fish community composition and diet overlap between round gobies and native species were surveyed in 1994 and compared with similar data from 2011. Fish were collected in trawls (3, 5, 7, 9, 11 m depths) and seines (1 m) in May, June, and September 1994, and May, July, and September 2011. Between 1994 and 2011, relative abundance of northern madtom (Noturus stigmosus) decreased significantly in the offshore zone, catch-per-unit effort (CPUE) for rainbow darter (Etheostoma caeruleum) and round goby significantly decreased in the nearshore zone while CPUE for channel darter (Percina copelandi), johnny darter (Etheostoma nigrum), mottled sculpin (Cottus bardii), and round goby significantly decreased in the offshore zone. In 1994 and 2011, adult round gobies consumed mainly zebra or quagga mussels (Dreissena polymorpha; D. bugensis). Significant diet overlap between large round gobies and native rock bass (Ambloplites rupestris), logperch (Percina caprodes), and trout-perch (Percopsis omiscomaycus) occurred infrequently in 2011. Decreasing round goby abundance may be due to increased predation by native species. Negative impacts of the round goby invasion and establishment on fish species diversity within this part of the St. Clair River were confined to a few species and possibly due to competition for other resources, such as space.