Case Study: Sea Lamprey

The sea lamprey currently represents a significant economic and ecological threat to the American Great Lakes region. First discovered in Lake Ontario in 1835, the sea lamprey soon spread throughout the area and reproducing populations were found in all of the Great Lakes by 1947. It is speculated that the sea lamprey, which is a marine species, was introduced to the lakes after migrating through the Erie Canal or "hitchhiking" on boat hulls and host fish. Its introduction was probably aided by the use of larval lampreys as bait by sport fishers.

The sea lamprey survives by attacking and parasitically feeding on other fish, which often results in death of the prey. This parasitism led to the collapse of commercial fisheries in many parts of the Great Lakes during the 1950s and 1960s. The parasitic sea lamprey caused the decline of lake trout and walleye populations and was also a major reason for the extinction of longjaw cisco, deepwater cisco, and blackfin cisco. The United States spends over $12 million annually on trout restoration programs to combat the damage done by sea lampreys.

In 1955, the Convention on Great Lakes Fisheries between the United States and Canada was signed. The Convention established the Great Lakes Fisheries Commission, whose purpose is to control and eradicate the sea lamprey at an estimated cost of $10 million annually. The main method of control used is the lampricide 3-trifluoromethyl-4-nitrophenol (TFM), which is a chemical agent that kills larval lampreys. TFM has reduced the sea lamprey population by 90% of its 1961 peak, but this strong lampricide often harms other fish species, which raises questions about its continued use. Other techniques for control include special barriers to prevent lamprey entry and the release of sterile males.

- Fuller, P.L., L.G. Nico, J.D. Williams, Nonindigenous Fishes Introduced into Inland Waters of the United States

(Bethesda, MD: American Fisheries Society, 1999). p. 19-21

- Corn, M.L., J. Rowson, E.H. Buck, E. Fischer, "CRS Issue Brief for Congress- Harmful Non-Native Species:

Issues for Congress RL30123," (Washington, DC: Congressional Research Service, April 8, 1999)

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