To determine differences in round goby and yellow perch habitat preferences.
To determine behavioral interactions between round goby and yellow perch in dreissenid and macrophyte habitats

The invasion of the round goby is likely to have complex effects on yellow perch populations in the Great Lakes. Round goby may compete with benthivorous yellow perch for macroinvertebrates, causing a negative effect on perch growth rate and therefore restricting the recruitment of yellow perch to piscivorous stages. Furthermore, competitive interactions in aquatic systems are affected by habitat complexity. Macrophytes may provide yellow perch with a refuge from the competitive interaction and facilitate coexistence between the exotic and native fish. Also species-specific behavior could be important in determining the outcome of round goby-yellow perch interaction. Round goby aggressive behavior may limit yellow perch to habitats with lower food resources. However the level of aggression may vary on between habitats (mussels vs. macrophytes). This study will be conducted simultaneously with a field cage experiment testing the effect of round goby on yellow perch growth rates. Information about yellow perch habitat choice and behavioral interactions between yellow perch and round goby will clarify the mechanism underlying the potential effect of round goby on yellow perch populations.

We will conduct short-term lab experiments (24 hrs) to test habitat preference of round goby and yellow perch among low (open sand) and high (macrophytes and dreissenids colonies) complexity habitats. We also will test for the effect of round goby presence on habitat preferences on yellow perch. We will conduct long-term experiments (1 month) to test for behavioral response of yellow perch to interspecific and intraspecific competitors in both habitats. In these experiments we are planning to compare growth rate of yellow perch in the different treatments (absence and present of competitors).