Ruffe (Gymnocephalus cernuus) were introduced to North America in the Duluth, Minnesota--Superior, Wisconsin harbor, which is the westernmost point on the Laurentian Great Lakes. The species proliferated in the harbor and became the subject of research which has gradually revealed certain characteristics of the biology and population growth of the ruffe. In this study, ruffe in Southwestern Lake Superior were found to have eaten benthic organisms and eggs of lake herring (Coregonus artedii). Overwinter predation by ruffe on eggs of lake herring and of other fall spawning Great Lakes fishes might pose a substantial new source of overwinter mortality.
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Predation by ruffe (Gymnocephalus cernuus) on fish eggs in Lake Superior