Changes in age-0 yellow perch habitat and prey selection across a round goby invasion front

Round gobies (Neogobius melanostomus) are reported to have negative impacts on benthic invertebrate prey and are now highly abundant throughout most of the Laurentian Great Lakes. This study used the initial spread of round gobies north and south from the Milwaukee Harbor as a natural experiment to assess the competitive interactions between age-0 yellow perch and round gobies in western Lake Michigan. Habitat selection and diet of age-0 yellow perch in relation to round goby abundance were analyzed using fish captured in micro-mesh gillnets in 2006 and 2007 at six study locations from Sheboygan to Wind Point, Wisconsin. An age-0 yellow perch shift in habitat preference from rock to sand was associated with relatively high round goby abundance at rock sites. An increase in round goby catch per unit effort was also correlated with a decrease in benthic prey (chironomid larvae+amphipods) abundance at rock sites and occurrence of these prey items in age-0 yellow perch stomach contents. Our results suggest that age-0 yellow perch may have undergone local niche shifts as a consequence of competition with round gobies. Further study may help elucidate the causal mechanism behind our observations and determine what effect round gobies are having on the yellow perch population of western Lake Michigan, as a whole.