Control crews will be back on the water this spring to fight one of the Great Lakes' most destructive invasive species: sea lampreys.
The Great Lakes Fishery Commission (GLFC) says its 2025 treatment season begins at the end of April in Lake Erie and Lake Ontario tributaries, as teams from Fisheries and Oceans Canada and the U.S. Fish and Wildlife Service begin efforts to remove the parasitic predator.
Though unfamiliar to many residents today, sea lampreys remain a potent ecological and economic threat. These eel-like parasites latch onto native fish like lake trout, whitefish, and walleye, feeding on their blood and bodily fluids. While the adult lamprey only feeds for about 18 months, each one can kill up to 40 pounds of fish in that time.
Greg McClinchey, Director of Policy and Legislative Affairs for the GLFC, says the situation is far from under control without continuous intervention.
"If the Great Lakes Fishery Commission were to not do its control job, then between three to five years we wouldn’t have any fish left." McClinchey said.
McClinchey describes the sea lamprey as an "absolutely existential threat to the Great Lakes." Though native to the Atlantic Ocean, lampreys found their way into the Great Lakes over a century ago through man-made shipping canals. Since then, they’ve caused massive disruptions to native fish populations, devastated the commercial and recreational fishing sectors, and triggered cascading impacts throughout the broader ecosystem.
To combat the species, Canada and the United States signed the Convention on Great Lakes Fisheries in 1955, forming the binational GLFC. Since then, the Commission has carried out annual treatments involving lampricides (primarily TFM), as well as the installation of barriers and traps to limit reproduction and migration. TFM is highly targeted to affect lampreys while sparing most other aquatic species, but the public is still advised to avoid exposure and suspend irrigation for 24 hours during treatment periods.
Lampricide application remains the most effective tool in the Commission’s arsenal, but the battle is ongoing.
"If the Fishery Commission was to reduce its control efforts by just 30 percent," McClinchey said, "that would leave an extra 2.5 million sea lampreys in the system every year. Those lampreys would eat about 12 to 14 million pounds of fish."
That, he adds, could translate to nearly $270 million in direct losses annually, and that’s before factoring in broader economic damage to tourism, cottaging, and other sectors dependent on the health of the lakes.
Despite these stark numbers, public awareness of the issue remains limited. McClinchey says this is both a good and a bad thing.
"It means we’re doing our job," he said. "People become aware of things when a crisis emerges. The fact that a lot of people might not be aware of this means the sea lampreys aren’t causing the kind of havoc they once did. But it’s a bad thing because we need people to know what we’re doing."
To help raise awareness, GLFC participates in outreach events across the basin, including school visits and appearances at events like the Owen Sound Salmon Spectacular. They also engage lawmakers on both sides of the border to ensure continued support for the program.
This year's field season was nearly delayed by staffing challenges within the U.S. Fish and Wildlife Service, but public pressure and political support have helped ensure that work can begin as scheduled. GLFC Executive Secretary Marc Gaden said the Commission is "extremely grateful" for that support. "Sea lamprey control in the Great Lakes is essential, proven effective, and a clear example of the efficiency possible through effective partnerships," said Gaden.
Ethan Baker, Chair of the Commission, added that despite the late start in planning, "those that have dedicated their career to protecting the $5.1 billion Great Lakes fishery are doing everything they can to make up for the lost time."
The Great Lakes Fishery Commission also supports science coordination across the basin, helping ensure that decisions about stocking, quotas, and ecosystem health are grounded in real research. McClinchey says this approach has already paid off, pointing to a major milestone reached last fall.
"We were able to announce that lake trout populations in Lake Superior have been fully restored,” he said. “That’s a pretty remarkable thing when you think of all of the pressures placed on these populations."
With nearly 70 years of sea lamprey control under its belt, the Commission warns that any let-up in effort will lead to a rapid rebound in lamprey numbers. That makes consistent funding, staffing, and public understanding all the more crucial.
More details about the Sea Lamprey Control Program, including the 2025 treatment schedule and public advisories, can be found at glfc.org.