GRAND RAPIDS, Mich. (WOOD) — The U.S. and Canadian governments shut down their borders for 19 months during the COVID-19 pandemic, but it may have inadvertently opened the door for sea lamprey.

The parasitic fish is considered an invasive species in the Great Lakes. While the population has largely been under control for the past few decades, experts believe we will see a rise in the next couple of years.

Marc Gaden, the legislative liaison for the Great Lakes Fishery Commission, says the group’s work was greatly impacted by the pandemic. He said the commission performed only 35% of its scheduled lampricide treatments in 2020 and 75% in 2021.

“Most of the lampricide treatments that we were able to do in 2020 and 2021 consisted of day trips near the lamprey control stations,” Gaden told News 8. “There are three lamprey control stations. There’s one in Marquette, there’s one in Ludington and there’s one in Sault Ste. Marie, Ontario. So we were really limited to what we could do.”

A lot of the treatment map can be handled by one crew, either on the American or the Canadian side. But for some locations, including here in West Michigan, the commission needs the full team to get the job done.

“Some large treatments, like the Manistee River or the Muskegon River, it’s all hands on deck,” Gaden said.

Those lost treatments could allow more lamprey to successfully breed and make their way to the Great Lakes, feasting on fish and hurting the bottom lines of the region’s fisheries.

“The lamprey spawn in the springtime and the ones that are spawning in the spring of 2022 are the survivors of a 2020 treatment,” Gaden said. “So we’ll start seeing what kind of numbers we get this spring and it will start to give us an indication of how many lampreys really survived.”

The question is: How big of an impact could this have on the lakes?

“We’re cautiously optimistic that it won’t be huge because the numbers in many areas of the Great Lakes, especially Lake Michigan, were below target going into 2020. So the numbers were very, very low and potentially provided us with some wiggle room,” Gaden said.

An up-close look at a sea lamprey’s mouth. They use their mouth like a suction cup to attach onto other fish and drink their blood and other body fluids. (Courtesy Great Lakes Fishery Commission)


Sea lamprey are native to the Atlantic Ocean but by the 19th century had made it into Lake Ontario. Niagara Falls served as a natural barrier, keeping the lamprey out of the other four Great Lakes. However, changes to waterways around the falls, including the Welland Canal, gave them an opportunity to expand, eventually making their way to all five Great Lakes.

Sea lamprey were first found in Lake Michigan in 1936 and by the 1950s were shown to be a major menace on the lake’s ecosystem. At that time, they were killing off an estimated 110 million pounds of fish each year, far more than the commercial harvest; not only a threat to Great Lakes fish, but the fishermen who made their living on the lakes.

“Incredibly destructive,” Gaden said. “The people who were fishing the lakes watched in relatively slow motion, a horror as the lamprey wiped out their way of life and their business. So by the 1950s, it became apparent that if we wanted to save the Great Lakes fishery, we needed to control the sea lampreys.”

Enter the Great Lakes Fishery Commission. In 1954, the Canadian and American governments signed a treaty called the Convention on Great Lakes Fisheries. It organized the efforts of the Great Lakes states and Canada, making their programs more effective. The sea lamprey control program has been particularly successful.

“We’ve reduced the lamprey populations by about 90% to 95%,” Gaden told News 8. “Basin-wide, we’ve gone from losing about 110 million pounds of fish every year to only about 10 million pounds. … We’ve gone from about 600,000 voracious sea lampreys in Lake Michigan to about 15,000, 16,000.”

This photo shows a brown trout with a sea lamprey bitemark on its side. (Courtesy Great Lakes Fishery Commission)

Sea lamprey feed on several types of fish, most notably lake trout and lake whitefish, but they also feed on walleye, steelhead and yellow perch. Lamprey aren’t a major threat to ocean fisheries because the fish on which lamprey feed can often survive and work in a symbiotic relationship. Lucas Nathan, the aquatic invasive species coordinator with the Michigan Department of Natural Resources Fisheries Division, said lamprey are such a big problem on the lakes because they don’t have a major predator.

“Typically, when invasive species are introduced, they have a bigger impact because other species didn’t co-evolve with them,” Nathan told News 8. “They are not necessarily suited to survive that attachment.”

In some cases, the simplest way to get rid of an invasive animal is to introduce one of its predators, as well, but that can have a far-reaching and often negative impact.

“In some instances, introducing predators to control invasives can be effective,” Nathan said. “Typically, it would be more in the suppression real as opposed to achieving full eradication. There’s risk, though, that’s always present in introducing another non-native species to control a different one. … On anticipated impacts, you know, introduce a predator, thinking it will exclusively feed on this because (that’s what it does in its native habitat). That’s not necessarily the case. It might find something else to prey on. And then we have a different invasive species that we’re grappling with.”


When the Great Lakes Fishery Commission launched, finding an effective treatment to kill sea lamprey was a top priority.

“It’s very, very easy to kill fish, but it’s very difficult to kill just the fish you want to kill and to leave the other fish on harmed,” Gaden said.

After running more than 10,000 experiments, scientists landed on a “silver bullet” — a specific concentration of a chemical that can be safely added to the water that kills lamprey but doesn’t harm other fish.

Sea lamprey live anywhere from four to 10 years and follow a specific life cycle. Adult lamprey swim to streams to spawn where females lay up to 100,000 eggs. The larvae stay buried in the stream bed for anywhere from 3 to 10 years, feeding on plankton and other organic material. Once they mature, they head back into the lakes and feed on fish for a year before returning to the streams to spawn and die.

The Great Lakes Fishery Commission targets streams for the majority of the region’s treatments because they know all lamprey spend time in that type of ecosystem at some point in their life, whether as an adult returning to spawn or as an egg or larvae hiding in the stream bed.