The battle against invasive sea lamprey in the Great Lakes rages on

Image of a sea lamprey Photo by T. Lawrence/Great Lakes Fishery Commission

For the past two years, COVID-19 impeded conservation operations in the Great Lakes. Now, the Great Lakes Fishery Commission is ramping up efforts to contain invasive sea lampreys that threaten the wellness of the ecosystem.

Sea lamprey management is a fickle but important part of Great Lakes conservation. Since the 1950s, Canada and the U. S. have been working in tandem to keep the invasive species in check and preserve the $7 billion Great Lakes fishing industry. However, in 2020 and 2021, pandemic restrictions prevented conservation workers from undertaking their usual ecosystem management efforts in the Great Lakes.

In the past, when control was eased, lamprey populations grew relatively quickly. However, Marc Gaden of the Great Lakes Fishery Commission, which is in charge of sea lamprey management, says the organization is hopeful that renewed containment efforts will keep the population in check this time around. “We’re cautiously optimistic that we can weather this,” says Gaden.

What’s happening right now?

The pandemic limited the Commission’s capacity to work in the field and manage lamprey populations. The Fishery Commission’s lamprey management operations were only able to run at roughly 25 per cent capacity in 2020, and 75 per cent in 2021. “COVID set us back a bit, the past two seasons have been highly curtailed because the crews couldn’t get out there,” Gaden explains.

The lampreys that are spawning now, are survivors from the 2020 season. This means the Commission won’t know until the fall, once they’ve fully analyzed all the available data, how significantly the population has changed.

Still, Gaden is cautiously optimistic about the situation. The Commission had been aggressively controlling the sea lamprey population in the decade leading up to COVID-19, which happened to set them up well for the pandemic, says Gaden. “We went into COVID as well-positioned as you can be for a disruption of that size.”

Both the Canadian and American governments have provided the Great Lakes Fishery Commission with additional resources, allowing them to step up the battle against the sea lampreys, says Gaden. Now, the Commission is working at maximum capacity to apply the lampricide treatments. “We’re well-positioned from a resource position to really take this battle to the lamprey and to continue to suppress the populations to the target level we’ve set.”

What are sea lampreys?

Sea lampreys have been a thorn in the side of Great Lakes conservationists for a century. They’re ancient blood-sucking creatures with eel-like bodies and rows of concentric teeth. While the creatures are healthy contributors to their natural environment off the Atlantic coast, they’re devastating to the fish of the Great Lakes. 

From a scientific point of view, even though sea lamprey are a huge pest in the Great Lakes, lampreys as a whole are evolutionarily pretty fascinating,” says Margaret Docker, a professor at the University of Manitoba who studies lamprey biology and freshwater fish conservation. Sea lampreys began to evolve half a billion years ago. The ancient sea creatures are often mistakenly referred to as eels thanks to their long and skinny bodies, but they’re actually considered jawless fish. “Almost all the lineages of jawless fish went extinct, and lampreys are one of the few survivors from that time, 400 million years ago,” says Docker.

Parasitic sea lampreys use their jawless but teeth-lined mouths to suction onto a host fish. Then, they use their tongue—which also has its own set of teeth—to chisel away at the flesh of their prey to suck up its blood. For those who are now scared to dip their toes into the Great Lakes, have no fear, sea lampreys only go after cold-blooded prey.

Docker says the larger fish of the Atlantic are able to handle the sea lamprey’s bite, which makes them little more than a nuisance (like a very large mosquito) in their native habitat. But for the smaller freshwater fish of the Great Lakes, the sea lamprey’s bite is often fatal.

Sea lamprey attached to a salmon
Photo by M. Gaden/Great Lakes Fishery Commission

Why are sea lamprey harmful to the Great Lakes?

The vampire-like fish was first seen in Lake Ontario in the mid-1800s, but it wasn’t until the 1930s that sea lampreys were documented in all five lakes. Gaden says sea lampreys entered the Great Lakes through man-made canals, and the Great Lakes happened to serve as the perfect habitat for the invasive creatures. It provided them with optimal spawning grounds, a plethora of tasty fish, and most importantly, a lack of natural predators. “That’s kind of the best recipe you could possibly have if you’re an invasive species,” says Gaden. “Those are the best conditions for an invasion.”

Gaden says prior to the late 1950s, sea lampreys inflicted enormous damage to the ecosystem of the Great Lakes. Individual sea lampreys are capable of killing 20 kilograms of fish and each female can lay 100,000 eggs. After their invasion, sea lampreys quickly decimated the fish populations of the Great Lakes. “They put some commercial fishers out of business,” says Gaden. “In some cases, they were eating more fish than humans were catching.”

In 1954, Canada and the U.S. joined forces to create the Great Lakes Fishery Commission, which they tasked with managing the Great Lakes ecosystem and containing sea lamprey populations. Gaden says the creation of this bi-national organization is a testament to how destructive the sea lamprey is. While the commission has had success and setbacks over the past half a century, today, lamprey numbers are only at a small fraction of what they were prior to control efforts, he says. 

The secret weapon in the fight against lampreys? Lampricide. Lampricide is a pesticide discovered by the Commission that kills lampreys while leaving other wildlife in the Great Lakes unharmed. “It’s a wild success story in terms of taking a species that essentially posed an existential threat to the Great Lakes, and bringing it under control using mechanisms that are safe for the environment and harmful to lampreys,” Gaden says.

It’s crucial that conservation efforts continue to ensure sea lampreys don’t expand beyond the Great Lakes, says Docker. 

Featured Video