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Tuesday, February 7 • 8:40am - 9:00am
Symposia Session - S7: Uncommon Techniques with Predators and Prey. Walleye in the Western Basin: What Diets Reveal About Foodweb Changes After Multiple Species Invasions of Western Lake Erie

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AUTHORS: Dana Castle*, U.S. Geological Survey Great Lakes Science Center and University of Toledo, Department of Environmental Sciences; Ed Roseman, U.S. Geological Survey, Great Lakes Science Center; Kevin Keeler, U.S. Geological Survey Great Lakes Science Center and University of Toledo, Department of Environmental Sciences; Carson Prichard, U.S. Geological Survey Great Lakes Science Center and Central Michigan University, Department of Biology; Robert Hunter, U.S. Geological Survey, Great Lakes Science Center and Michigan State University, Department of Fisheries and Wildlife; Chris Vandergoot, Ohio Department of Natural Resources; Mark Rogers, U.S. Geological Survey, Great Lakes Science Center, Lake Erie Biological Station; Kristen Hebebrand, University of Toledo Department of Environmental Sciences; Brian Schmidt, U.S. Geological Survey, Great Lakes Science Center; Christine Mayer, University of Toledo Department of Environmental Sciences; William Taylor, Center for Systems Integration and Sustainability, Department of Fisheries and Wildlife, Michigan State University

ABSTRACT: Lake Erie supports the world’s largest walleye (Sander vitreus) population, where they play an important role as a top predator and provide valuable ecological and economic benefits. In western Lake Erie, year-class strength is measured as the survival of age-0 fish to their first fall after larval walleye transition to demersal juveniles. Therefore, foraging patterns and food web interactions during the larval and juvenile stages critically influence the sustainability of Lake Erie walleye. To determine factors (temperature, prey energy density, rate of consumption, etc.) that influence larval and juvenile walleye growth over time, including the impacts of invasive species on diet, we compared a historic (1994-95) and current (2014) dataset. Using the R-based Fish Bioenergetics 4.0, we (1) determined which factors are most likely to influence individual growth between time periods and (2) predicted impacts of likely prey community scenarios on walleye diet, such as an increase in the proportion of round goby (Neogobius melanostomus) consumed. We found walleye collected in 2014 maintained higher consumption rates throughout the summer and fall to achieve similar growth rates as fish collected during the 1990s, likely due to consumption of less energy-dense invasive species (round goby, Bythotrephes, Dreissenids). The model predicted that this rate of consumption would continue to rise as walleye consumed a higher proportion of round goby. Despite foodweb and diet changes between time periods, mean fall lengths of walleye were similar, suggesting similar growth rates. Revelation of differences in the underlying factors affecting larval and juvenile growth rates over time and under varying prey scenarios can provide fishery managers unique insight about age-0 walleye growth and recruitment.

Tuesday February 7, 2017 8:40am - 9:00am
Grand Ballroom A

Attendees (18)