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Richards, C., A.E. Hershey, R.P. Axler, and J.A. Schuldt, 1997. Experimental Investigations into the Effects of Ruffe on Aquatic Food Webs, University of Minnesota-Duluth Proceedings of the International Symposium on Biology and Management of Ruffe, March 21-23, 1997 Experimental Investigations into the Effects of Ruffe on Aquatic Food WebsABSTRACT. The recent establishment and population expansion of Eurasian ruffe (Gymnocephalus cernuus) within the Lake Superior watershed has raised several questions concerning the role of ruffe in Great Lakes aquatic ecosystems. We conducted two mesocosm experiments to investigate the effects of ruffe on aquatic food webs. During 1995, we tested the effects of ruffe on benthic and pelagic invertebrate populations by comparing mesocosms containing ruffe to fishless mesocosms in a paired design. We found that ruffe significantly (p < 0.05) reduced Chironomidae and Ceratopogonidae abundance, but did not affect zooplankton populations. During 1996, we tested the effects of fish density (low or high) and fish community structure (yellow perch or yellow perch plus ruffe) on benthic and pelagic populations using a factorial design. We found that Oligochaete abundance was affected by fish density and the presence of ruffe, while Chironomidae abundance was affected only by fish density. Zooplankton abundance did not differ between treatments. Contact: Carl Richards, Natural Resources Research Institute,
University of Minnesota-Duluth, Duluth, Minnesota 55812 or crichard@d.umn.edu |