Sea lamprey are native to the Northern Atlantic Ocean and are actually a delicacy in some European countries, but this is not the case everywhere… Sea lamprey invaded the Great Lakes in 1930s and are now adapted to live their whole life in freshwater in Great Lakes. Sea lamprey are by far the most destructive of all invading species in the Great Lakes and they are currently present in all Great Lakes.

While there is more than one type of lamprey in the Great Lakes (including some native species), sea lamprey are much bigger and much more abundant than any other! They are known to be an aggressive and resilient invasive species. Sea lamprey are a parasite, feeding on the blood and inner fluids of their prey. Sea lamprey literally suck the life out of their host fish, by using tooth-filled, suction cup mouth and file a hole through the fish’s scales and skin with a razor-sharp tongue. The sea lamprey prey on many important fish such as trout and salmon, which has depleted many native stocks for fisheries, negatively affecting the $7 billion Great Lakes fishery industry. The average sea lamprey kills 40 pounds of fish every year, they do this by leaving bite wounds that become infected and can lead to disease.

The sea lamprey’s life starts as larvae in a small river or stream where they stay as immobile filter-feeders (3+ years). As they grow larger, they emerge from the streambed and head down stream into open water. Sea lamprey go through a stage of metamorphosis (like a butterfly) which changes large components of their bodies, including allowing them live in sea water (salt water) in their native range. This is also where they begin their parasitic life stage in open water, feeding on anything they can attach to (mostly large fish), this lasts about a year (12-18 months). When sea lamprey are ready to spawn, they stop eating and move upstream to spawn and die, since many sea lamprey are in rivers or streams at the same time during spawning and larvae stages, this is most often where control techniques are used.

Scientists currently use a variety of different techniques to control lamprey (traps, barriers, and chemicals). Traps and barriers are used to block spawning lamprey from moving upriver to spawn or for physically removing lamprey. The problem with both are that they affect non-target species (like the creek chub and white suckers) that also swim upstream during the same time of year (spring) but some traps are designed specifically to catch sea lamprey. Lampricide, a pesticide specific to lamprey, is also used, this is a chemical dumped into the water during or after lamprey spawning, that kills the babies of the lamprey before they grow up into their most devastating life stage. When used individually, none of the control methods work enough to keep the sea lamprey in check. This is because one sea lamprey female makes over a thousand eggs, which have high survival rates (60,000 eggs w/ 90% survival). The best control method is using multiple methods to increase the efficiency. For example, traps used with pheromones (smells) that will either attract or repel the sea lamprey into traps, increasing the amount caught.

Industry professionals, non-profit organizations, and government agencies have come together to create a successful control program and will continue to work together to improve the program efficacy on controlling this invasive species!

You can learn more about sea lamprey by visiting our species profile, here.

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Sea Lamprey (Petromyzon marinus)
French common name: Lamproie de mer

Sharp teeth radiate around a rasp-like tongue at the centre of a large sucker mouth.

Sea lamprey tank

Sea lamprey in a tank.
Photo by Joanna Gilkeson/USFWS

Sea lampreys are among the oldest invaders of the Great Lakes.
Photo by C. Krueger, GLFC

Order: Lamprey

Did you know? Only one in seven fish attacked by sea lamprey survive.

The Sea Lamprey is a primitive, eel-like fish that invaded the Great Lakes in the early 20th century through shipping canals. In their native range of the northern Atlantic Ocean and the Baltic, western Mediterranean and Adriatic seas, they live part of their lives in salt water, but they have adapted to living entirely in fresh water in their invaded range of the Great Lakes. As adults, they spawn in rivers and streams and their larvae live on organic matter in stream bottoms until they transform into parasites that migrate into lakes. Their mouth is a large sucker with rings of sharp teeth and a raspy tongue that is used to latch onto the side of a fish and feed on its blood. Adults spend 12 to 20 months feeding on the blood of other lake-dwelling fish, until they are ready to travel upstream to spawn, and die shortly after. The complete life cycle usually lasts five to nine years. Sea Lamprey have significantly reduced the number of sportfish in the Great Lakes, as only one in seven fish survive an attack.

How to Identify Sea Lamprey (from the Ontario fact sheet)


  • Cylindrical bodies are 30-76 cm long with no scales
  • Leathery skin is grey to dark brown with dark blotches and a lighter belly
  • Sharp teeth radiate around a rasp-like tongue at the centre of a large sucker mouth
  • The fish has large eyes, two dorsal fins, no pelvic or pectoral fins, a single, mid-dorsal nostril, and seven obvious gill openings on each side


  • Larvae are up to 18 cm long, blind, and wormlike, with a black to pale grey body and a light underside
  • In larvae that are 4 cm or longer, the first and second dorsal fins are distinctly separate



The native range of the sea lamprey includes the Atlantic coast of North America from Newfoundland to northern Florida, the Atlantic coast of Europe, and the Baltic, western Mediterranean, and Adriatic seas. Today, sea lamprey are also found in all of the Great Lakes. Sea lamprey larvae live in Great Lakes tributaries that have suitable habitat until they become juveniles or “transformers.”

According to the Great Lakes Fishery Commission, sea lamprey predation on valuable fish stocks was so high in the 1940s it became a key factor in the collapse of the Great Lakes ecosystem and economy that it supported. Tens of thousands of jobs were lost, property values were diminished, and a way of life was forever changed for millions of people. Sea lampreys killed more than 100 million pounds of Great Lakes fish annually, five times the commercial harvest in the upper Great Lakes.

The devastating impact of sea lamprey on Great Lakes sport, commercial, and Indigenous fisheries in the 1940s and 50s led Canada and the United States to form the Great Lakes Fishery Commission in 1955. Since then, the commission has led a program to assess and control the species using measures that target different stages of its life cycle. Control measures include chemicals that selectively kill lamprey larvae and barriers and traps that prevent adult lampreys from moving upstream to spawn. Although it is likely impossible to eliminate sea lamprey from the Great Lakes, ongoing efforts to control the species have reduced populations by 90%. Unfortunately, the remaining sea lamprey continue to affect native fish species.

  • Sea lamprey use their sucker mouth, sharp teeth, and rasping tongue to attach to the body of a fish and suck the fish’s blood. Fish that survive the attack are left with a large open wound that can become infected and often leads to death.
  • During its parasitic phase, one sea lamprey can destroy an average of 18 kg of fish.
  • As few as one in seven fish may survive a sea lamprey attack. Attacks have resulted in reduced stocks of lake trout, salmon, whitefish, cisco, and burbot in the Great Lakes.

Learn how to identify and prevent the spread of this unwanted species.

  • Don’t release any live fish into Canadian waters.
  • Don’t help sea lampreys pass over dams and culverts that block their spawning migration.
  • If you catch a fish with a sea lamprey attached, do not return it to the water. Kill it and put it in the garbage.
  • For questions, contact the Sea Lamprey Control Centre of Fisheries and Oceans Canada at 1-800-553-9091.
  • Report other invasive species sightings to the Invading Species Hotline at 1-800-563-7711, or visit to report a sighting.

Fact Sheets

Best Management Practices

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Potential for carbon dioxide to act as a non-physical barrier for invasive sea lamprey movement

… support the use of carbon dioxide as a barrier to deter the movement of lampreys … include cost/application logistics, potential negative impacts on non-target organisms, potential impacts

Evaluating the growth potential of sea lampreys (Petromyzon marinus) feeding on siscowet lake trout (Salvelinus namaycush) in Lake Superior

… habitat in which lampreys can feed; however, our simulations indicate that lampreys can grow …Bioenergetically, siscowets are viable lamprey hosts and should be given more consideration in future 

[PDF] Sea lamprey control: past, present, and future

… to concentration or timing of lampricide treatments, because field observations of non-target impacts since the … presence in the head waters of tributaries above barriers provides a refuge from Sea Lamprey control activities and a source of Brook Lampreys to repopulate …

Current Projects

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Further Reading

The Invasive Species Centre aims to connect stakeholders. The following information below link to resources that have been created by external organizations.