We evaluated the diet of Lake Whitefish Coregonus clupeaformis in Lake Huron during 2002-2011 to determine the importance of Round Goby Neogobius melanostomus and other fish as prey items. Lake Whitefish that had reached approximately 400 mm in length incorporated fish into their diets. The overall percentage of adult Lake Whitefish in Lake Huron that had eaten fish increased from 10% in 2002-2006 to 20% in 2007-2011, with a corresponding decrease in the frequency of Dreissena spp. from 52 to 33%. During 2002-2006, Round Goby (38%, wet mass), sculpins (Cottidae) (34%), and Ninespine Stickleback Pungitius pungitius (18%) were the primary fish eaten, whereas Round Goby accounted for 92% of the fish eaten in 2007-2011. Overall, Round Goby were found in the fewest lake whitefish stomachs in the north region (6%) and the most in the south (19%) and central (23%) regions. In the central region, Round Goby were eaten during all seasons that were sampled (spring through fall), but in the south region, round gobies were eaten only in winter and spring, but not in the summer, when Dreissena spp. and spiny water flea Bythotrephes longimanus dominated the diet. Based on the 2007-2011 diet composition, an individual Lake Whitefish would need to have increased consumption relative to 1983-1994 only by 6% in the north region, 12% in the central region, and 41% in the southern region in order to achieve the same growth that was observed before dreissenid mussels arrived. However Lake Whitefish weight adjusted for length only increased by 2% between 2002-2006 and 2007-2011 in the central region, decreased by 4% in the northern region, and remained constant in the southern region. This suggests that a shift toward more frequent piscivory does not necessarily improve condition of a generalist feeder like Lake Whitefish.
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Increased piscivory by lake whitefish in Lake Huron