General Informatiom:

The ruffe is a small but aggressive fish native to 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 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. The ruffe starts reproducing at age two or three but can reproduce after the first year in warmer waters. 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. 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.

WARNING!  Under state laws, it is illegal to possess a ruffe, dead or alive, in Michigan, Wisconsin, Minnesota and Ontario.

Copyright, 1998, by the University of Wisconsin Sea Grant Institute
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