Sea Lamprey

  • Sea Lamprey

    (Petromyzon marinus)

    The Sea Lamprey is one of the most commonly known invasive species in the Great Lakes region. Although the primitive, eel-like fish is known to be native to the northern Atlantic Ocean and the Baltic, eastern Mediterranean and Adriatic seas, it has been suggested it is also native to Lake Ontario, Lake Champlain and the Finger Lakes in New York State. It was first observed in Lake Ontario in 1935, 12 years after the Erie Canal opened from New York to Buffalo. Whether it is a native or not in Lake Ontario, it is an invasive species in the other Great Lakes, where it was first observed in the 1930s.

    Sea Lamprey begin their lives as small, wormlike larvae, which feed on organic matter on stream bottoms for about 3 to 6 years before transforming into adults. The adults migrate into the Great Lakes to feed on fish for 12 to 20 months before swimming upstream to spawn and die.

    A parasitic feeder, the Sea Lamprey latches onto large fish with its sucker mouth, sharp teeth and rasping tongue and sucks blood from the host.

    Control methods include barriers and traps on streams, release of sterilized males and lampricides targeting the larval stage.


    Sea Lampreys are found in the Great Lakes, the St. Lawrence River, Lake Champlain and the Finger Lakes, with the larval stage living in tributaries of those water bodies.

  • Identification

    • Although ocean-dwelling Sea Lampreys range up to 1.2 metres in length, fresh-water Sea Lampreys only reach up to 30 to 76 cm.
    • Lampreys are not eels. Members of an ancient family of jawless fishes, they have a circular sucker mouth with sharp teeth radiating around a rasp-like tongue.
    • Sea Lampreys have leathery skin without scales that ranges from grey to dark brown with dark blotches and a lighter belly.
    • Usually found attached to a host fish, they have large reddish eyes, seven gill openings on each side, two dorsal fins from the midsection to the tail and a skeleton formed from cartilage.
    • The larvae grow up to 18 cm long, are blind and wormlike with black to pale grey bodies and lighter bellies.
    • Larvae 4 cm in length or longer have distinctly separate dorsal fins.
    • Similar native species include: Silver Lamprey (Ichthyomyzon unicuspis), Chestnut Lamprey (I. castaneus), Northern Brook Lamprey (I. fossor), American Brook Lamprey (Lampetra appendix) and American Eel (Anguilla rostrata).


    • One Sea Lamprey can eat up to 18 kg of fish during its lifetime.
    • As few as one in seven fish survive Sea Lamprey attacks; many fish are left with an open wound that can become infected and lead to death.
    • The parasite devastated the Great Lakes fishery, which plummeted from annual harvests of about 6.8 million kgs before the infestation to about 136,077 kgs in the early 1960s.
    • It reduced Great Lakes stocks of Lake Trout, Salmon, Whitefish, Cisco and Burbot.

    How can you help?

    • Learn to identify the Sea Lamprey and how to prevent further spreading of this parasite.
    • Do not release live fish into Ontario waters.
    • Do not assist Sea Lamprey to pass over dams or culverts blocking migration upriver.
    • Do not return Sea Lampreys to the water when caught attached to fish. Kill and put in the garbage.
    • If you have any questions about the Sea Lamprey, contact the Sea Lamprey Control Centre of Fisheries and Oceans Canada in Sault Ste. Marie at 1-800-553-9091.
    • Report other invasive species sightings to the toll-free Turtle Island Invaders hotline at 1-844-872-2348 (1-844-TRACE-IT) or to your local Lands or Natural Resources officer.
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