Sea Lamprey: A Great Lakes Invader
Sea lampreys are aquatic vertebrates native to the Atlantic Ocean. Sea lampreys resemble eels, but
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.
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 Erie, sea lampreys moved rapidly to the other Great Lakes, appearing in Lake St. Clair in 1934, Lake Michigan in 1936, Lake Huron in 1937, and Lake Superior in 1938. By the late 1940s, sea lamprey populations had exploded in all of the upper Great Lakes causing sever damage to lake trout and other critical fish species.
Sea lampreys attach to fish with their sucking disk and sharp teeth, rasp through scales and skin, and feed on the fish’s body fluids, often killing the fish. During its life as a parasite, each sea lamprey can kill 40 or more
pounds of fish. Sea lampreys are so destructive that under some conditions, only one of seven fish attacked by a sea lamprey will survive.
Sea lampreys have had an enormous negitive impact on the Great Lakes fishery. Because sea lampreys did not evolve with naturally occurring Great Lakes fish species, their aggressive, predaceous behavior gave them a strong advantage over their native fish prey. Sea lampreys prey on all species of large Great Lakes fish such as lake trout, salmon, rainbow trout (steelhead), whitefish, chubs, burbot, walleye and catfish.
Sea lampreys were a major cause of the collapse of lake trout, whitefish and chub population in the Great Lakes during the 1940s and 1950s. These fish were the mainstay of a vibrant and important fishery. Before the sea lamprey’s spread, the United States and Canada harvested about 15 million pounds of lake trout in the upper Gre Lakes each year. By the early 1960s, the catch was only about 300,000 pounds. In Lake Huron, the catch fell from 3.4 million pounds in 1937 to almost nothing in 1947. The catch in Lake Michigan dropped from 5.5 million pounds in 1946 to 402 pounds by 1953. The Lake Superior catch dropped from an average of 4.5 million pounds to 368,00 pounds in 1961.
During the time of highest sea lamprey abundance, up to 85% of fish somehow not killed by sea lampreys
exhibited sea lamprey wounds. (Scott and Crossman, Freshwater Fishes of Canada.) The once thriving fisheries were devastated. Great Lakes sea lampreys themselves, traditionally, have had no economic value.