Winter distributional overlap facilitates lake whitefish (Coregonus clupeaformis) piscivory on invasive round gobies (Neogobius melanostomus) in Green Bay, Lake Michigan

Abstract

The prevalence of round goby (Neogobius melanostomus) in the diet of lake whitefish (Coregonus clupeaformis) >350 mm total length was investigated during winter, when round gobies occupy deeper water and have distributional overlap with lake whitefish. On average, round gobies were the most important diet item (46.6% by dry weight), followed by nonmollusk benthic invertebrates (21.3%) and unidentifiable fish parts (10.6%). Of whitefish that contained food, round gobies were the most frequently occurring diet item (49% occurrence); 44.3% of whitefish examined had empty stomachs. Although lake whitefish are not generally considered piscivores, altered lake whitefish diets have been observed during a recent period of high lake whitefish density and reduced abundance of historically important prey like Diporeia spp., which declined in the Great Lakes following the invasion of Dreissena polymorpha and D. bugensis. There is evidence that fish provide an important summer diet item for lake whitefish in some areas of the Great Lakes, and our study suggests round gobies are also an important component of lake whitefish diets during winter.