-Fisheries managers in Lake Superior first tried to control ruffe by increasing the number of its predators, especially walleye and northern pike. They did this by limiting sport catches of these species, and stocking walleye and northern pike. Results of the predator-stocking program were disappointing.
-Researchers analyzed stomach samples of the predators and found very few ruffe in walleye stomachs. Bullheads appear to be the only species that consistently eat ruffe. Research suggests that predators stocked to control ruffe may not eat them because they prefer soft-rayed shiners and small hard-rayed fish like darters and young perch.
-Surveys of northern pike stomachs, however, suggest that ruffe may be growing in importance as a food source. Ruffe made up less than one percent of fish eaten by northern pike in 1989. By 1992, the figure had climbed to 15 percent. Poisoning ruffe in some areas was considered, but was ruled out.
-To keep ruffe from spreading to the other Great Lakes, the Lake Carriers Association developed best management practice guidelines for handling ballast water in Great Lakes ships.
-Other methods that have been considered are poison and chemical control. If a large school of ruffe is found, they can be poisoned. If some of them survive, however, the problem will only continue. Chemicals, on the other hand, can be specifically made to only harm a certain kind of fish. The chemical lampricide TFM kills ruffe, but leaves other fish untouched.
-The major problem with this though, is that as long as a couple of the fish survive, they can move and repopulate. The problem would increase if the ruffe started to move farther down south. A new method of control is being investigated to prevent this: pheromones. After an extensive amount of tests, scientists discovered that the ruffe can be repelled by their own alarm pheromone. When injured, a ruffe will release this pheromone into the water to warn other ruffe to stay away. After doing these tests, the scientists involved concluded three significant things. One, that the pheromone does repel the ruffe (it was unclear if it would in the beginning). Second, the pheromone is species specific, so it would only repel the ruffe, none of the other fish. Finally, the scientists found that it is resilient to freezing, so even during Minnesota's long winter season; the ruffe could still be controlled. By using this method there is a chance the ruffe could be prevented to go to their natural mating spots and therefore eventually the ruffe might die out.
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