Interspecific Competition Between Round Gobies and Logperch

The round goby is an aggressive benthic fish native to the Ponto-Caspian region of Eurasia and has become invasive in the Laurentian Great Lakes.  Competition for food and habitat are hypothesized to lead to the competitive exclusion of native species.  We sought to determine the extent of interspecific competition between the round goby and the logperch.  Enclosures constructed of PVC and black plastic mesh screening were placed in the St. Louis River Estuary containing both interspecific and intraspecific treatments of round gobies and logperch.  Fish Growth in each enclosure was measured after 28 days.   Experiments were conducted on two different substrates, rock and sand, and multiple trials were conducted throughout spring and summer.  When paired with a round goby, logperch lost more weight than the round goby, regardless of the substrate, although gobies only exhibited positive growth on sand.  Our findings suggest that the round goby poses a threat to native logperch populations on rock and sand substrate.