Great Lakes Fishery Commission reports significant increase sea lamprey populations in the five Great Lakesfollowing relaxed efforts since the COVID-19 pandemic.
This invasive species, which feeds parasitically on fish, poses a threat to the region’s $7 billion fishery.
Sea lampreys, accidentally introduced through shipping channels into the Great Lakes in 1921, use their mouths filled with 150 teeth and toothed tongues to attach themselves to their prey, killing up to 40 pounds of fish during their parasitic stage.
Before sea lamprey control, this species killed far more fish than humans, causing considerable economic and ecological damage.
In 1958, control programs were implemented that previously reduced populations by more than 90%, but the pandemic halted the slowing of population growth in 2020 and 2021. As a result, millions of sea lamprey larvae survived, leading to the population increase seen today.
In 2024, the number of adult sea lampreys was 8,619 higher than pre-Covid averages. All five Great Lakes are exceeding population targets, with Lake Superior and Ontario seeing the largest increase. Populations in Lakes Michigan, Huron and Erie have begun to stabilize as treatment gradually resumes.
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“The increased abundance in all lakes is not unexpected given the significant reduction in control efforts in 2020 and 2021 due to the pandemic,” said Ethan Baker, commission chairman and mayor of Troy, Michigan.
“We should expect high and variable abundances of adult sea lampreys over the next couple of years before declining again. »
A sea lamprey’s mouth has 150 teeth and a toothed tongue.
Steve Russell/Toronto Star via Getty Images
Sea lamprey control remains a joint effort between Canada and the United States, involving treatments, barrier maintenance and research.
“The sustained increase in sea lamprey abundance highlights the continued need for sea lamprey control and research into new and innovative control methods in the Great Lakes,” said Jim McKane, vice president of the commission.
Even if current populations remain above targets, further control efforts must be maintained to safeguard one of the world’s most important freshwater ecosystems.
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