The bloodthirsty invasive fish that haunts the Great Lakes – Reuters

They have the body of a eel, the mouth of a sarlac, and the diet of a vampire.

The sea lamprey is a fish native to the Atlantic Ocean and the rivers that drain into it. But more than a century ago, they found their way into the Great Lakes region, where they multiplied and became one of the most destructive invasive species in US history.

These creatures are parasites. To feed, fish grab onto, burrow in, and begin sucking blood and body fluids, often killing their prey in the process. A single lamprey can kill up to 40 pounds of fish; And their hordes are threatening the Great Lakes fishing economy, which is estimated to be worth about $7 billion a year.

Lake Huron salmon with attached sea lamprey.
Mark Gaden/Great Lakes Fisheries Commission


The lamprey is the largest species of lamprey. Here, two eels were caught in the Great Lakes.
Marilyn Levison/Star Tribune via Getty Images

Wildlife officials in the Great Lakes region have been eliminating sea lampreys for several decades, largely using lamprey-specific pesticides. But paradoxically, marine lampreys are on the verge of extinction in parts of their native habitat, including western Europe and the northeastern United States. Four species of native lamprey also live in the Great Lakes region, which wildlife officials are trying to protect.

This raises a fundamental tension, common in invasive biology: how we treat a species depends largely on where it is, even if humans put it there. Appearance is also important. Unfortunately, the Great Lakes glaciers are unlucky on both sides.

What is a sea lamprey?

The sea lamprey is up to a meter in length and is the largest of the 40 species of lamprey, a truly ancient group of animals. They have been on Earth for more than 350 million years, and have experienced at least four major extinctions.

They are also a strange group. Like sharks, sea jellyfish have no bones. Like salmon, it swims downstream to breed and can live in both salty and fresh water; And like frogs, they go through metamorphosis.

Then there are those mouths. They are filled with concentric circles of teeth made of keratin (the substance of your hair and nails), which they use to suck their prey. After holding the hole, they dig into the flesh with a beak-like tongue.


Sea lamprey larvae killed by the pesticide lamprey in Michigan.
R. McDaniels / Great Lakes Fisheries Commission

Aussi horrible que cela puisse paraître, les lamproies sont une aubaine pour les écosystèmes le long de la côte Est et en Europe occidentale, où elles sont indigènes, selon Margaret Docker, biologiste à l’Université les qui de lampétoies de 35 years. Lampreys, like caterpillars, are food for a variety of aquatic animals. The larvae live in a stream, consuming dead or decaying matter that other animals cannot eat, helping to move nutrients up the food chain.

After a few years (and sometimes much longer), lamprey larvae morph and become parasites, developing new mouths, working gills and eyes, and exiting the stream en masse, Duker said. “Lots of other marine mammals and fish are waiting at the mouth of the river for this flood of lampreys,” she said.


Merganser catches a common lamprey in Dumfries, Scotland.
David Tipling / Education Images / Global Image Collection via Getty Images

Even if they are pests, sea lampreys are not a problem in their native range. They live in a “peaceful coexistence” with other fish, Duker said. Sea snakes tend to search for larger fish, which can better survive an attack. They also have plenty of natural predators, including catfish, and other threats like dams, so there aren’t many.

How eels became villains in the Great Lakes region

Most species are becoming “invasive” because of humans, whether it’s a predatory snail spreading north due to climate change or parachute guru spiders likely to travel to the United States on a container ship. Sea lampreys are no exception. They arrived in the Great Lakes region during the 19th century, most likely through the construction of canals. (Some scholars believe sea lampreys are native to Lake Ontario. There is also a broader debate over the term “invasive.”)


Lake trout caught in Lake Superior with a sea lamprey sting.
Jerry Holt/Star Tribune via Getty Images

With plenty of fish and few natural predators, eels thrived in the Great Lakes. And in the 1940s, they were in the top five, according to the book Great Lakes Lamprey: The Seventy Years’ War against the Bioinvader by Lamprey researcher Cory Brant.

At the same time, fisheries in the area have collapsed. The United States and Canada harvest about 15 million pounds of lake trout each year from the upper Great Lakes region. But in the 1960s, that number dropped to 300,000 pounds, just 2% of what it used to be. The South Bend Tribune reported in the spring of 1953 that “sea lampreys threaten to completely destroy the fishing industry of the Great Lakes.” .)

Wildlife officials in the area were not shy about resisting. In 1954, the United States and Canada joined forces and created an organization called the Great Lakes Fisheries Commission (GLFC). Its mission was primarily – and still is – to kill sea snakes.

Government attack on the lamprey

The nation’s attack on sea snakes is one of the best organized and funded efforts to control any invasive species. Their main weapons are lampreys, two types of insecticides that target lampreys but do not appear to harm most other fish. (Scientists discovered it in the 1950s after painstakingly examining more than 7,000 substances.)

Each year, wildlife officials dump about 175,000 pounds of liquid lamprey into streams that flow into the Great Lakes, where they kill lampreys in their larval forms (they also harm native lampreys). Authorities also rely on dams or small levees to prevent sea jellyfish from migrating upstream to spawn.

In a typical year, GLFC — which spends about $25 million annually on eel control — kills about 7 million sea jellyfish. So far this year, the death toll has reached 1.7 million, according to the murder tape on his website.


Barriers like these help prevent sea jellyfish from swimming upstream until they spawn.
M. Moriarty / US Fish and Wildlife Service

Pesticides do their job well. Sea snakes once destroyed more than 100 million pounds of fish each year in the Great Lakes, but today they kill less than 10 million pounds, according to the GLFC. According to experts, this likely has many benefits for non-commercial fish and other organisms.

But even those gains are rather weak, according to Robert McLaughlin, a biologist at the University of Guelph in Ontario. “Whenever this control loosens, they quickly start to fall back,” he said. “Their number is not that high at the moment, but that’s because we’ve been controlling them for nearly 70 years.”

Those responsible for wildlife are far from completely eradicating the animals. Mark Gaden, GLFC’s director of communications and legislative communications, said that although gelc can kill 98% of larvae in a given stream, this leaves some behind to create the next generation. He said that a female lamprey can produce more than 100,000 eggs. “You can’t have every single one of them,” he said, and going the last mile would be very expensive.


Sea snakes have impressive mouths.
Steve Russell/Toronto Star via Getty Images

Scientists are now exploring more creative ways to suppress sea jellyfish, including the use of scents and pheromones. Some pheromones attract lampreys, allowing scientists to lure them into traps, while the concentrated smell of dead lampreys repels them. (This video shows what happens when you add lamprey repellent to a tank. Warning: It’s a bit horrific.)

Certainly, eel control has benefited the fish and those who depend on them in the Great Lakes region. But it’s worth noting that these efforts threaten the region’s native lamprey – which are also susceptible to lampreys – and could harm markets everywhere. The authors of a recent study wrote: “In the case of sea lamprey in its native range, there is little doubt that the public imagination has been adversely affected by the need to control the species in the Great Lakes.”

The lamprey is considered “critically endangered” in parts of the eastern United States and “critically endangered” in parts of Europe, not to mention other lamprey species, many of which are critically endangered. However, says Kelly Robinson, professor of ecology at Michigan State University, “everyone thinks eels are awful because of the Great Lakes.”

If nothing else, you will probably remember that sea snakes (and other invasive species) are not inherently evil, or primitive as they may seem. Some countries even revere them as a food source. And even if you’re traveling to the Great Lakes region and planning to go swimming, you don’t have to worry. The sea lamprey prefers fish to warm-blooded animals.

Leave a Comment