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Sea Lamprey Overview

Petromyzon marinusSea lamprey illustration.

Lifecycle Overview 

  • Sea lamprey spend 1 – 3 years in the ocean parasitizing large fishes and sharks feeding on blood and body fluids.  During spring, sea lamprey leave the ocean and ascend large coastal rivers and streams, sometimes migrating upwards to hundreds of kilometers.  They construct pit and mound rock nests, spawn, and then die shortly afterwards.  Upon hatching, juveniles or “ammocoetes” drift downstream and burrow into fine sediments.  There, they filter feed and grow for up to 8 years.  Eventually the ammocoetes will undergo metamorphosis, developing an eye and oral mouth disk, and migrate to the ocean to begin the parasitic phase.


  • Sea lamprey are ubiquitous to temperate waters of the Atlantic ocean.  They occur in North America from Labrador to the Gulf of Mexico and inland among coastal drainages.  They are also native to the Mediterranean and the western European coast northward along Scandinavia.  Sea lamprey are invasive to the Great Lakes of North America and millions of dollars are spent annually to control populations and range expansion.

    History of the Fishery

    • Historically, sea lamprey were harvested for food in Europe, and today small fisheries remain in localized areas, however there is little commercial value or interest for them in Maine or North America.  Very small markets exist for harvesting sea lamprey for biological research and school dissection.  While they have little to no commercial value in Maine, they are important sources of nutrients to freshwater food webs and benefit other anadromous and resident fishes through their nest-building activities.

     Current Status and Management 

    • Sea lamprey are not currently listed as threatened or endangered, but are likely in decline, and thus have been acknowledged in conservation management plans in Europe and North America.  Some natural resource agencies have only recently begun to keep records of annual returns of sea lamprey and thus it is uncertain how current trends stack up to historical abundances.  Sea lamprey are likely negatively affected by migration barriers (i.e., dams), degraded freshwater spawning habitat, and declines in large pelagic fishes that serve as their food base in the ocean.

    Current Recovery Efforts

    • Currently there are no concerted efforts that specific target sea lamprey, however they benefit directly from management strategies seeking to restore alewife, American shad, and Atlantic salmon populations through dam removal and improved fish passage techniques.  Current research has begun to identify the importance of sea lamprey as a keystone species that alter stream habitats through spawning and provide marine-derived nutrients to freshwater systems.

    Links, Useful documents


    Prepared by:
    Dan Weaver
    University of Maine
    American Fisheries Society Student Subunit 

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