According to new research conducted by the U.S. Geological Survey (USGS) this year, the COVID-19 pandemic may have given invasive lamprey populations a nearly tenfold boost in the Great Lakes.
The species, sea lamprey (not to be confused with Pacific lamprey, which are native to the Pacific Northwest and are facing declining populations), is a voracious parasitic fish that suction onto host species like lake trout and brown trout, wreaking havoc on their populations.
Historically, sea lamprey are relatively new to the Great Lakes, but they quickly changed the aquatic ecosystem when the man-made Welland Canal provided passage around Niagara Falls for the first time in 1938. Within 25 years, the commercial lake trout harvest dropped from about 15 million pounds per year to less than half a million pounds, as a result of the lamprey invasion.
In response, the newly formed Great Lakes Fishery Commission began experimenting with lamprey-specific poisons (“lampricides”) in the 1960s to kill the juvenile, larval stage of lamprey. Like salmon, lamprey spawn in freshwater creeks, and the larval offspring spend several years in the rivers before migrating to the Great Lakes and attaching to other fish species. The operation proved wildly successful at knocking back lamprey populations and reviving the lake trout fishery, but it was no small feat. Continuing today with a budget of around $20 million per year, the Commission treats about 200 tributary streams per year with lampricide to maintain the precarious equilibrium.
That balance, however, could be more tenuous than previously thought, according to the new research. During the 2020 and 2021 COVID shutdown, control operations came screeching to a halt due to both state-specific lockdown measures and the inability of field crews to cross between the U.S. and Canada. Tributaries to Lakes Ontario and Erie didn’t receive a single lampricide treatment in 2020, while other lakes saw around 45% of usual field crew efforts, at most. More streams were treated in 2021, but efforts still fell short of targets.
It took several years for the impacts of the missing treatments to be realized, but the data now suggest that lamprey populations took quick advantage of the slack. “Like a coiled spring, sea lamprey populations bounced back quickly when control was relaxed,” said lead researcher Benjamin Marcy-Quay in a press release.
In the two years following COVID, lamprey abundance spiked significantly in all the lakes, with Superior and Ontario seeing the biggest increases. In Superior, lamprey abundance jumped from pre-COVID estimates of around 25,000 to about 65,000 in 2022 and 2023. Similarly, Ontario saw a jump from around 5,000 pre-COVID to a post-COVID peak of 60,000. Additionally, the researchers noted an increase in sport fish with lamprey scars in all but one lake (Erie).
“Wounding on Chinook and coho salmon, specifically, increased over 10-fold in Lake Ontario,” said Marcy-Quay. “Our findings support observations by the fishing public and fishery managers of fish riddled with sea lamprey wounds, some containing three or more wounds per fish.”
However, some good did come of the missed treatments, according to the researchers. COVID offered a unique opportunity to actually measure the effectiveness of an invasive species treatment regime. And the important conclusion? Not only is lamprey control successful, but it’s also critical to the well-being of the Great Lakes—especially the commercial fishery, which is valued at $5.1 billion and supports about 35,000 jobs. For reference, the Bristol Bay sockeye fishery—which received attention with regard to the Pebble Mine—is worth $2 billion and employs about 14,000 people.
Despite that knowledge, the Trump administration’s Department of Government Efficiency took aim at the lamprey control program this spring. On Valentine’s Day of this year, 14 U.S. Fish & Wildlife Service employees who administer the treatments were fired, right before the field season was set to begin.
“This simply puts us in a place where we don’t know if we’re able to actually run a program in the year ahead,” Greg McClinchey, policy director for the Great Lakes Fishery Commission, told Great Lakes Now after the firings. “We know that if lamprey are left in the system, it has pretty immediate and pretty massive economic and ecological implications,” he said in another interview. Given the outsized impact and importance of the lamprey control work, local people were generally outraged and on edge by the layoffs.
Fortunately, the Trump administration heeded the pressure and in mid-March allowed 12 of the program’s staff members to be rehired. Several opted not to return, according to a local news outlet. Still, the upheaval set the field season back several months—a delay that could have impacts, given the newfound sensitivity of lamprey populations to consistent poison treatments.
Still, the fiasco—in conjunction with COVID—exposed the vulnerability of the Great Lakes to potential resurgences in lamprey. A single female can lay up to 100,000 eggs, meaning the species can make quick work of repopulating—at the expense of other commercial and sport-fish species.
“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,” said Commission chair Ethan Baker, in response to the new research. So for now, it’s pedal to the metal on lampricide usage, and hopefully it will remain as such until another solution can be found to maintain the balance in the Great Lakes.
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