Ruffe / Fish of the Great Lakes by Wisconsin Sea Grant

Ruffe

Ruffe
Gymnocephalus cernuus

Length: 4 to 6 inches(25 cm)

Coloring: olive-brown to golden-brown on back, paler on the sides with yellowish white undersides

Common Names: Eurasian ruffe, river ruffe, pope

Found in Lakes: Huron and Superior

The ruffe is a small but aggressive fish native to fresh and brackish waters in portions of Eurasia. It was introduced into Lake Superior's Duluth/Superior harbor area in the mid-1980s in the ballast water of an trans-oceanic ship.

In Europe, the ruffe generally matures and begins to reproduce in two or three years, but it may mature in one year in warmer waters. It spawns between mid-April and July, depending on location, water temperature and preferred years. An average female can produce 130,00 to 200,000 eggs per season.

A relative of the perch, the ruffe spends its days in deeper water and moves to the shallows to feed at night. Ruffe in the Great Lakes seem to be most common in or near river mouths. To avoid predators, the ruffe prefers darkness, and uses special sensory organs called "neuromasts" to detect predators and prey. The ruffe also has a large, spiny dorsal fin likely unpalatable to predators.

Because the ruffe grows very fast, has a high reproductive capacity and adapts to a wide variety of environments, it is considered a serious threat to commercial and sport fishing. It also has the potential to seriously disrupt the delicate predator/prey balance vital to sustaining a healthy fishery.

Local laws vary regarding the possession of ruffe. Take a look at your state or province regulations, and contact your local authorities if you need more information.

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copyright University of Wisconsin Sea Grant Institute
Brook Trout illustration copyright 1998 Gina Mikel
Ruffe photo copyright Gary Cholvek/National Biological Service
Last updated 05 February 2002 by White