Bloodsucking Sea Lampreys Made a Comeback in the Great Lakes During Covid

Travel restrictions hindered population control of the invasive parasites, which feed on fish like trout, whitefish, perch and sturgeon

Sea lamprey mouth
A sea lamprey USGS - GLSC

Invasive, bloodsucking sea lampreys are startling fishers and tourists alike in the Great Lakes, following a population spike during the Covid-19 pandemic. With long, skinny bodies and circular mouths lined with sharp teeth, the fish have been among the region’s most unnerving—and destructive—inhabitants since they arrived nearly 200 years ago. 

“We’re very happy that they’re not cute like bunnies, because it would be much harder to convince people that we need to rid the Great Lakes of them,” Greg McClinchey, legislative affairs and policy director for the Great Lakes Fishery Commission, tells the Wall Street Journal’s Joe Barrett. “They are unquestionably the stuff of nightmares.” 

Sea lampreys (Petromyzon marinus) are native to the Atlantic Ocean as well as the Baltic, western Mediterranean and Adriatic seas, per the National Park Service. They are just one of 31 total lamprey species. In their native range, lampreys are considered to be keystone species and act as ecosystem engineers, supporting both aquatic and terrestrial ecosystems. They serve as food for a variety of creatures and provide spawning habitats for fish, and their larvae help maintain water quality, writes Ted Williams for Yale Environment 360. Lampreys have existed on Earth for more than 340 million years, surviving four major extinction events and remaining largely unchanged since they evolved. 

But in the freshwater environment of the Great Lakes, the parasitic creatures do not have natural predators, and they are much more deadly to the fish they feed on. A lamprey uses its suction cup mouth to attach to prey, including trout, whitefish, perch and sturgeon. With its sharp tongue, the lamprey rasps away at the fish’s flesh to feed on its blood and body fluids, per the National Oceanic and Atmospheric Administration. Just one sea lamprey can kill 40 pounds of fish per year, per the administration. Though females die shortly after spawning, they can lay as many as 100,000 eggs

Sea lampreys were first documented in the Great Lakes in 1835 in Lake Ontario. For years, Niagara Falls served as a natural barrier to prevent the fish from spreading to the other lakes, but by 1938, improvements to the Welland Canal between Lake Ontario and Lake Erie, bypassing the falls, allowed the invasive species to spread to the entire system. By the 1960s, the creatures had devastated the upper Great Lakes’ trout fishery, reducing the take of lake trout from about 15 million pounds to just half a million pounds, per Yale Environment 360.

“They are incredibly destructive,” Marc Gaden, deputy executive secretary of the Great Lakes Fishery Commission, tells Cortney Moore of Fox News.

Since 1958, the Great Lakes Fishery Commission, a partnership between the United States and Canada, has been combatting the population of sea lampreys with a dedicated control program. Over that time, the species’ numbers have dropped by about 90 to 95 percent in the basin, rebuilding the lakes’ fishing economy, Gaden tells the publication. Lampricide, a pesticide discovered in 1957, is used to control the sea lamprey population in streams where their larvae live, along with traps and barriers. At the concentrations used, lampricide affects only lampreys. Controlling the creatures costs between $15 million and $20 million per year.

But travel restrictions during the pandemic in 2020 and 2021 hindered crews from applying the pesticide. As a result, sea lamprey numbers swelled, which became evident in 2022, because the animals’ spawning cycle leads to a two-year lag in population trends.

“We’ve been hitting the lamprey hard in 2022 and 2023,” Gaden tells Fox News. “We’re hoping the Covid spike was a blip.”

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