Sea lamprey
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 Sea lampreys on a trout
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| Petromyzon marinus (Linnaeus, 1758) |
The sea lamprey (Petromyzon marinus) is a parasitic lamprey found on the Atlantic coasts of Europe and North America, in the western Mediterranean Sea, and in the Great Lakes. It is brown or gray on its back and white or gray on the underside and can grow to be up to 90 cm (35.5 in) long. They prey on a wide variety of fish by attaching themselves with their mouths to the skin of a fish and rasping away tissue with its tongue and teeth. Secretions in the lamprey's mouth prevent the victim's blood from clotting. Victims typically die from blood loss or infection.
The life cycle of sea lampreys is anadromous, like that of salmon. The young are born in inland rivers, live in the ocean as adults, and return to the rivers to breed. Young emerge from the egg as larvae, blind and toothless, and live that way for 3 to 17 years, buried in mud and filter-feeding. Once they have grown to a certain length, they metamorphosize into their adult form, after which they migrate to the sea. After about 12 to 20 months, they return to the rivers and streams and spawn, after which they die.
Sea lampreys are considered a pest invasive species in the Great Lakes region. Though they have always been found in Lake Ontario, they entered the other lakes through the Welland Canal and rapidly colonized the Great Lakes region. They have created a problem with their aggressive parasitism on key predator species and game fish, such as lake trout, whitefish, chub, and lake herring. Elimination of these predators allowed the alewife, another invasive species, to explode in population, having adverse effects on many native fish species. Control efforts, including electric current, chemical lampricides, and barriers, have met with fair success.
