Sea Lamprey

A 'bloodsucking monster' that feeds on fish blood, which once nearly collapsed the fisheries of North America's Great Lakes. Sea lampreys originally lived in the Atlantic Ocean but entered the Great Lakes over 100 years ago through canals dug by humans. They attach themselves to fish with their disc-like mouths full of sharp teeth, then use their tongues to bore into the fish, causing continuous bleeding. In the worst cases, a single lamprey could kill a fish weighing up to 18 kilograms. But facing this invasive species with virtually no natural predators, scientists eventually found a 'targeted weapon' – one that could kill large numbers of lampreys without harming native fish.