Species At Risk

Silver Lamprey

(Ichthyomyzon unicuspis)

Special Concern (Great Lakes – Upper St. Lawrence River Population)


The silver lamprey is an eel-shaped fish with a sucking disc mouth. Like all lampreys, it does not have jaws or paired fins. Adult silver lampreys range from nine to 39 centimetres long. Young lampreys have yellow to tan/grey backs, becoming darker as adults, with a light blue-grey to silver belly.

Silver lampreys are very difficult to correctly identify. Experts must rely on differences in fin shapes and teeth arrangements to distinguish between them and other lamprey species.

Adult silver lampreys are parasites. They attach themselves to different host fish species, feeding on flesh and body fluids. They live for 12 to 20 months as parasites before migrating up streams to spawn, then die after spawning.

Action we are taking:


Outside Ontario, the silver lamprey is found in tributaries that feed the St. Lawrence River in Quebec and New York west through to Manitoba and tributaries of the Nelson River. Silvery lampreys are also found in the upper Mississippi River tributaries.


Silver lampreys require clear water so they can find fish hosts, relatively clean stream beds of sand and organic debris for larvae to live in, and unrestricted migration routes for spawning. Their use of different kinds of habitat throughout their lives (rivers for spawning and early development, and lakes for adults) makes them vulnerable to changes in their environment.


The Great Lakes - Upper St. Lawrence River population of silver lamprey is of Special Concern due to a variety of threats, including habitat loss and the use of lampricides – chemicals designed to kill lampreys used to control the invasive sea lamprey.

Dams that restrict the lamprey’s ability to migrate from lakes to breeding areas in streams pose a threat, along with chemical pollution, especially the widely used herbicide Atrazine.


The silvery lamprey is listed as a Special Concern species under Ontario's Endangered Species Act. It also has the general protection provided by habitat sections of the federal Fisheries Act.

What You Can Do to Help the Silver Lamprey

  • If you spot a silver lamprey, report your sighting to the Natural Heritage Information Centre (http://nhic.mnr.gov.on.ca/MNR/nhic/species/species_report.cfm) Observations submitted by the public are very important in informing recovery planning, stewardship projects and other conservation initiatives for species at risk in Ontario. Whenever possible, include detailed location information and a photograph with your observation.
  • Report any wildlife related infractions to 1-877-TIPS-MNR (847-7667).
  • Private landowners have an important role to play in species recovery. You may be eligible for stewardship programs that support protection and recovery of species at risk and their habitats. For more information visit Ontario.ca/speciesatrisk or contact the Ministry of Natural Resources at 1-800-667-1940.

Did you know?

Silver lampreys belong to the most ancestral lineage of vertebrates (animals with backbones). From them we may be able to learn about evolutionary pathways, such as the transition from jawless to jawed vertebrates.

Did you know?

Lamprey larvae have been used as bio-monitors to measure the health of the streams where they live. By monitoring the larvae, researchers can identify changes in population sizes and potential problems within their ecosystems.

Did you know?

Silver lamprey are one of five species of lamprey in Ontario whose larvae all look identical, making it difficult to distinguish juveniles of the species.

The Endangered Species Act

Contact your local ministry office

Often the best source of local information on species at risk is your nearest ministry office. Call with your questions or concerns.