From Great Lakes Wiki
The Eurasian ruffe is a small spiny fish that spends it's days in deeper waters and moves to shallow waters at night to feed. The ruffe has a small and spiny dorsel fin that is unpallatable to predators. An explosion in the population of the Eurasian ruffe means less food and less room in the ecosystem for other species of fish. While scientists have found the population of the Eurasian ruffle to be increasing in The Great Lakes, species like yellow perch and trout perch are on the decline. The ruffe is considered a great threat to commercial fishing.
