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Gymnocephalus cernuus

THE CRIMES: Competes with native fish. Eats incredibly large amounts of fish eggs and bottom-dwelling organisms.

DESCRIPTION: An olive-brown or golden-brown fish with rows of dark spots between its sharp spiny top fin. Has glassy eyes, one sharp spine on the fin underneath its front body and two very sharp spines on the fin underneath its back body. Usually is less than 15 cm (6 in.) long and very slimy when handled.

The Interrogation
Where are you from?
I came from both fresh water and brackish water in Europe and Asia.
How did you get here?
My boys and I jumped an ocean-going vessel around 1985 and hung out in its ballast water until we were dumped into the St. Louis River. By 1991 there were so many of us, we took over the St. Louis River. Since we feel at home in a variety of environments, we quickly moved to Lake Superior and eased into Lake Huron in the 1990s and have recently been found in northern Lake Michigan.
What’s your problem?
My alias says it all - I love to eat! My main diet consists of small aquatic insects, other bottom-dwelling organisms, and sometimes the eggs of other fish. As you can see I’m not a picky eater and I don’t hesitate to eat other’s food. Since our population grows so quickly and we eat so much food, your precious native walleye, yellow perch, and other small forage fish are going hungry. The only fish that considers me a delicacy is the Northern Pike.  My spiny fins keep the other fish away.
How can we control you?
Attempts to control me have failed, so humans are trying to educate as many people as possible to prevent me from calling another of the Great Lakes “home,” like Lake Erie or Lake Ontario. You can do your part by not using ruffe as bait.
Reward: The honor of protecting our water resources—A healthier environment and more opportunities to enjoy our natural areas.