Sea Lamprey Monitoring and Control

A close-up of a sea lamprey showing its hooklike teeth
The parasitic sea lamprey uses its hooklike teeth to latch onto fish.

Photo credit: Ted Lawrence, Great Lakes Fishery Commission

Sea lampreys are native to­­­­ the northern Atlantic Ocean and the Baltic, western Mediterranean and Adriatic seas. The first recorded observation of a sea lamprey in the Great Lakes was in 1835 in Lake Ontario. At that time, Niagara Falls served as a natural barrier, preventing these parasitic fish from entering the remaining Great Lakes. By 1938, thanks to improvements to the Welland Canal (which bypasses Niagara Falls and provides a shipping connection between Lakes Ontario and Erie) sea lampreys had spread throughout the entire Great Lakes system. These invasive fish were able to thrive once they invaded the Great Lakes because of the availability of excellent spawning and larval habitat, an abundance of host fish, a lack of predators, and their high reproductive potential—a single female can produce as many as 100,000 eggs!

Sea lampreys have had an enormous, negative impact on the Great Lakes fishery. Before their invasion, Canada and the United States harvested about 15 million pounds of lake trout in the upper Great Lakes each year. By the late 1940s, sea lamprey populations had exploded. They fed on large numbers of lake trout, lake whitefish, and ciscoes—fish that were the mainstays of a thriving Great Lakes fishery. By the early 1960s, the catch had dropped to approximately 300,000 pounds, about 2% of the previous average. During the time of highest sea lamprey abundance, up to 85% of fish that were not killed by sea lampreys were marked with sea lamprey attack wounds. The once thriving fisheries were devastated, and along with them, the hundreds of thousands of jobs related to the region’s economy.
The sea lamprey control program, administered by the Great Lakes Fishery Commission, relies on exploiting vulnerable sea lamprey when they are congregated in Great Lakes tributaries, at either the larval or adult stages of their life cycle. Lampricides—pesticides selective to lampreys and the primary sea lamprey control tactic—are deployed to kill larval sea lampreys in the tributaries, while a combination of barriers and traps are used to prevent the upstream migration and reproduction of adult sea lampreys.

The U.S. Fish and Wildlife Service is working in or near many of our Great Lakes National Parks to reduce the population of these invasive fish, and to prevent their spread into previously uninhabited waters. See Sea Lamprey Control in the Great Lakes for more information on the various sea lamprey control techniques. See Sea Lamprey Research for information on research and research opportunities.

This information was provided courtesy of the U.S. Fish and Wildlife Service.

Last updated: December 12, 2018