Eurasian Ruffe
Gymnocephalus cernuus
Where did the Ruffe come from?
The ruffe came to Lake Superior probably in the ballast water of a transoceanic ship in 1985. The ruffe is originally from fresh and brackish waters in portions of Eurasia. It is currently found in Lakes Superior, Huron, and Michigan.
Why is the Ruffe a problem? The ruffe is an aggressive fish. It has a rapid population growth. The ruffe eats a variety of foods. The ruffe has a lack of natural predators which creates the potential to displace other species in newly invaded areas and to cause the native fish populations to decrease. The average female can produce 130,000 to 200,000 eggs per season. The ruffe can reproduce after one year in warm water temperatures and the proper location. Spawning usually occurs between mid-April and July, depending on water temperature and location.
What does the Ruffe look like? The ruffe is olive-brown to golden-brown on back, and paler on the sides with yellowish undersides. The ruffe is slimy and has a large spiny dorsal fin that makes it undesirable to predators. The ruffe is a relative of the perch and spends its days in deeper water and comes to the shallows to feed at night. The ruffe also has special sensory organs that detect minute movements in the water to sense predators and prey.
How do we control the Ruffe? Always drain water out of your boat, live well, and bilge before leaving water access. Do not throw unwanted bait into the water, place it in the trash. Never dump fish from one lake into another. Never use ruffe as bait.
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