3D-Model representation

“Ruffe” (Gymnocephalus cernuus)

The ruffe (pronounced ruff), Gymnocephalus cernuus, has a yellow perch-like body shape with walleye markings and averages 4 to 6 inches in length. This small but aggressive fish was probably introduced into Lake Superior in 1985 via the ballast water of a transoceanic vessel. The ruffe was found in Lake Huron in 1995, and infects the Sand River in northern Wisconsin, Thunder Bay, Ontario and is now the most numerous fish in the St. Louis River. The ruffe's rapid population growth, variety of food it eats, and the lack of native predators create their potential to displace other species in newly invaded areas and to cause the eventual detriment of native fish populations.

Sources :  "Ruffe: A New Threat to our Fisheries" 1992. Minnesota Sea Grant. 
"Ruffe Maps" 1997. U.S. Fish and Wildlife Service.
Busiahn, T. R., 1996. "Ruffe -- A Case Study", U.S. Fish and Wildlife Service.
Slide: Doug Jensen, University of Minnesota Sea Grant Program.