The Great Lakes region is trying to fight off aggressive non-native species, which pose a major threat to other wildlife, human health, waterways and the economy.
Silver carp, one of three invasive carp threatening the Great Lakes, jump out of the water due to boat motor vibrations. (T. Lawrence, Great Lakes Fishery Commission)
Asian carp are threatening to enter the Great Lakes basin through the Chicago and Sanitary Ship Canal - a man-made canal which links the two basins. (T. Lawrence, Great Lakes Fishery Commission)
Sea lampreys attach to fish with a suction cup mouth ringed with sharp teeth; they bore a hole through the fish and feed on the fish's blood and body fluids. (T. Lawrence, Great Lakes Fishery Commission)
Left uncontrolled, sea lampreys - seen here feeding on a trout - could cause the collapse of the Great Lakes fishery. (US Fish and Wildlife Service)