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Conserving the Nature of America

The mission of the U.S. Fish and Wildlife Service is working with others to conserve, protect and enhance fish, wildlife, plants and their habitats for the continuing benefit of the American people.

Coronavirus (COVID-19) Notice

Although, outdoor recreation sites at national fish hatcheries and national wildlife refuges have remained open for the public to enjoy, we ask that you Recreate Responsibly.

  • Check local conditions online and call ahead for current information. Operations vary based on local public health conditions.
  • The CDC recommends all individuals wear a mask indoors in public in areas of substantial or high transmission. Recognizing that most of the United States is currently in substantial or high transmission categories and to best protect visitors and our staff, we’ve implemented a nationwide mask requirement. Masks are now required inside all U.S. Fish and Wildlife Service buildings, regardless of vaccination status or location. All people, regardless of vaccination status, are required to wear a mask on all forms of public transportation and in healthcare settings on DOI lands.
  • Most importantly, stay home if you feel sick and continue to watch for symptoms of COVID-19 and follow CDC guidance on how to protect yourself and others.

Learn more about the U.S. Fish and Wildlife Service Coronavirus Response.

Sea Lamprey

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

Sea lampreys are a jawless parasitic fish native to the Atlantic Ocean. Invading the Great Lakes via manmade locks and shipping canals, their aggressive behavior and appetite for fish blood wreaked havoc on native fish populations. Sea lampreys decimated an already vulnerable lake trout fishery.

Sea lampreys are naturally anadromous meaning they live in saltwater before migrating to freshwater to spawn. In the Great Lakes, sea lampreys have adapted their life cycle to live entirely in freshwater. Spawning adults deposit eggs in nests in Great Lake tributaries and once the eggs are hatched, the larvae burrow into the sediment where they spend anywhere from 3-7 years filter feeding on detritus, macroinvertebrates and dissolved organic material. After reaching sufficient size, larvae undergo a metamorphosis, growing eyes and an oral disk containing razor sharp teeth and a digestive system capable of feeding on fish blood. The newly transformed lamprey migrate downstream, heading for one of the Great Lakes in search of a host. Once in the lakes, they will spend 12-18 months parasitizing fish and feeding on their blood and body fluids. In that short amount of time, each parasitic lamprey is capable of destroying 40 pounds of fish. Sea lampreys prey on all large Great Lakes fish species including lake trout, salmon, rainbow trout, whitefish, walleye and catfish. At the end of their parasitic phase, they undergo another, less drastic transformation in preparation to spawn and head back upstream where they die after laying their eggs.


The Great Lakes were formed more than ten thousand years ago as glaciers receded at the end of the last ice age. These vast inland seas form the largest surface freshwater system on Earth and support 139 native fish species. The Great Lakes are significant to the history, culture, environment and economy of the midwest. They provide water for consumption, transportation, power and recreation. 

Sea lampreys are native to the Atlantic Ocean. In the 1800s sea lampreys entered into the Great Lakes system via manmade locks and shipping canals. Sea lampreys were first observed in Lake Ontario in the 1830s. Niagara Falls served as a natural barrier preventing sea lampreys from entering the other Great Lakes, but modifications to the Welland Canal in the early 1900s provided sea lampreys a path to invade the other lakes. In 1921 sea lampreys were first observed in Lake Erie and quickly spread into Lakes Michigan, Huron and Superior. 

Sea lampreys prey on most species of large Great Lakes fish such as lake trout, salmon, lake sturgeon, whitefish, burbot, walleye and catfish. The Great Lakes experienced a drastic decline in lake trout, whitefish and chub populations in the 1940s and 1950s brought on by overfishing, habitat degradation and the invasion of parasitic sea lampreys. 

The Sea Lamprey Control Program is administered and funded by the Great Lakes Fishery Commission and implemented by two control agents, the U.S. Fish and Wildlife Service and Fisheries and Oceans Canada, who often partner on larger projects.

During the 1950s the U.S. Fish and Wildlife Service sought to identify a chemical compound effective in controlling sea lampreys without significantly impacting other species. Scientists tested nearly 6,000 compounds in their research. The lampricide discovered has been used successfully for more than 60 years to suppress sea lamprey populations in the Great Lakes. By the early 1960s, the abundance of sea lampreys was reduced by 90%. This effort paved the way for the rehabilitation of a healthy Great Lakes ecosystem including the recovery of self-sustaining populations of native fish, such as lake trout, in portions of the Great Lakes. 

Continued chemical treatments and use of barriers have resulted in increasingly healthier fish populations and an economic powerhouse fueled by the sport fishery. Sea lamprey control will continue to be important as lake trout restoration activities and lake sturgeon recovery efforts expand in the Great Lakes. Sea lamprey control is critical in the establishment of a diverse salmonine community and supporting sustainable harvests of walleye, rainbow smelt and trout, smallmouth bass, yellow perch and whitefish.

How We Help

Sea lamprey control is a critical component of fisheries management in the Great Lakes because it facilitates the rehabilitation of important fish stocks by significantly reducing sea lamprey induced mortality. Control of sea lampreys is critical to restore lake trout, the native, keystone predatory fish in the Great Lakes, as well as protecting valuable commercial species such as lake whitefish and sport fishes such as Pacific salmons.

Marquette and Ludington Biological Station staff fulfill U.S. obligations under the 1954 Convention on Great Lakes Fisheries between the United States and Canada and the Great Lakes Fishery Act of 1956. We work with state, tribal and other federal agencies to monitor progress towards fish community objectives for sea lampreys in each of the Great Lakes, but also to develop and implement actions to achieve these objectives. Activities are closely coordinated with state, tribal and other federal and provincial management agencies, non-government organizations, private landowners and the general public. Our primary goal is to conduct ecologically sound and publicly acceptable integrated sea lamprey control.

Tribal Trust Responsibilities

Conserving fish and other aquatic resources cannot be successful without the partnership of tribes. They manage or influence some of the most important aquatic habitats within and adjacent to tribal territories. In addition, the federal government and the U.S. Fish and Wildlife Service have distinct and unique obligations toward tribes based on trust responsibility, treaty provisions and statutory mandates.

In August 2000, the U.S. District Court, Western District Court, Western District of Michigan Southern Division, issued a consent decree that specified how fishery resources will be managed in the portions of Lakes Superior, Huron and Michigan within ceded waters of the 1836 Treaty of Washington. The 2000 Consent Decree, based on a settlement agreement among the U.S., five tribal governments and the State of Michigan, addresses lake trout rehabilitation and requires that sea lamprey control efforts significantly reduce sea lamprey-induced lake trout mortality from 1998 levels. Failure to achieve a reduction in lamprey-induced mortality on lake trout within the 1836 Treaty waters could result in a party requesting relief from lake trout rehabilitation goals contained within the decree.