Action is finally being taken against an aggressive invasive species that has been surging across the Great Lakes in Ontario.
The spike in sea lampreys has triggered a joint campaign between Canada and the U.S. to protect the region’s $5.1-billion freshwater fishery.
Control crews began treatment in late April to decrease the population of 
this invasive species, which is known to parasitically feed on fish.
The work began in Lake Erie and Lake Ontario and will likely continue till October. Some of the population control methods include lampricides (a chemical treatment), traps and barriers.
Sea lampreys, also known as vampire fish, were accidentally introduced through shipping canals into the Great Lakes in 1921. They use their mouths with 150 teeth and serrated tongues to attach to prey, killing up to 40 pounds of fish during their parasitic stage.
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Before sea lamprey control, the species killed far more fish than humans did, causing considerable economic and ecological damage.
A new study confirms that lamprey numbers rose sharply during the COVID-19 pandemic. Travel restrictions in 2020 and 2021 forced crews to pause treatments and millions of lamprey larvae survived as a result.
Ethan Baker, chair of the Great Lakes Fishery Commission, said the rise was expected.
“Ongoing, consistent sea lamprey control is critically important for preventing damage to Great Lakes fish by invasive sea lampreys,” Baker said in an April 10 news release.
“Research shows that sea lamprey control must continue each year to keep populations of this harmful invasive species in check.”
In 2024, adult sea lamprey counts were 8,619 above pre-COVID-19 averages. Lake Superior and Lake Ontario saw the biggest increases. Numbers in lakes Michigan, Huron and Erie are starting to stabilize.
“If we take our foot off the gas, even for a short while, sea lamprey populations will increase rapidly and cause considerable damage to fish,” Baker said.
Control efforts have since resumed, but scientists and officials warn that the damage done during the pause will take years to reverse.
“Sea lamprey control is critical to safeguard the prosperity of the region,” Baker said.
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