Sea Lamprey: A Great Lakes Invader Sea lampreys are aquatic vertebrates native to the Atlantic Ocean. Sea lampreys resemble eels, but unlike eels, they feed on large fish. They can live in both salt and fresh water. Sea lampreys, now found in all the Great Lakes, attach to fish with a sucking disk and sharp teeth. Sea lampreys feed on body fluids, often scarring and killing host fish. To control this destructive aquatic nuisance, state, federal, provincial and tribal agencies in both the United States and Canada participate in the Integrated Management of Sea Lamprey (IMSL) process. The GLFC's program of integrated sea lamprey management includes lampricide control, construction of barriers in streams to deny sea lampreys' entry, and an experimental program to reduce spawning success by releasing sterilized-male sea lampreys. The program has successfully allowed the re-emergence of the largest freshwater fishery in the world. Sea lampreys (Petromyzon marinus) are primitive jawless fish native to the Atlantic Ocean. In the Great Lakes, there are several different types of native lampreys (including the silver lamprey, the American brook lamprey, and the northern brook lamprey) but the exotic sea lamprey is far larger and more predaceous than native lampreys.Although lampreys resemble eels, lampreys lack jaws and possess only cartilage. Lampreys have a large sucking disk for a mouth and a well-developed olfactory (sense of smell) system. The mouth is filled with horny, sharp teeth that surround a filelike tongue. A lamprey's body has smooth, scaleless skin, two dorsal fins, no lateral line, no vertebrae, and no paired fins. Sea lampreys are native to the Atlantic Ocean, not the Great Lakes. Sea lampreys entered the Great Lakes system in the 1800s through manmade locks and shipping canals. Prior to the opening of the Welland Canal in 1829, and prior to its modification in 1919, Niagara Falls served as a natural barrier to keep sea lampreys out of the upper Great Lakes. Sea lampreys were first observed in Lake Ontario in the 1830s. They did not invade Lake Erie prior to the improvements of the Welland Canal in 1919 ;sea lampreys were first observed in Lake Erie in 1921. After spreading into Lake