Smell of death repels sea lampreys

By Elizabeth Weise, USA TODAY

They're mean, ugly and a constant threat to fishing on the Great Lakes. But scientists at Michigan State University may finally have found a way to repel invasive sea lampreys: eau de dead lamprey. They've created a repellant using the scent of deceased lampreys that makes the live ones swim away.

Sea lampreys are sometimes called vampire fish because they have rings of sharp teeth that attach to the side of a fish, so they can "suck away flesh and blood — draining them until they die," says Michael Wagner, whose research on the new control method appears in the most recent edition of the Canadian Journal of Fisheries and Aquatic Sciences.

The eel-like fish first arrived in the Great Lakes when the Welland Canal was dug in the late 19th century, allowing lampreys from the Atlantic Ocean to bypass Niagara Falls.

They "virtually killed off the lake trout in Lakes Michigan, Huron and Erie, destroying both commercial and recreational fishing," says Mike Siefkes, sea lamprey program specialist with the Great Lakes Fishery Commission in Ann Arbor.

The program has reduced populations by about 90%, allowing the $7billion a year fishing industry to rebuild, Siefkes says. But it's expensive work that can't be stopped, as experiments have shown that they immediately begin to rebound.

Wagner and colleagues at Michigan State noticed that if someone had collected a bucket of the squirmy black fish during the day and a few had died, when they threw them back into a stream "all the other lampreys swam away," the fish ecologist says. He wondered if this alarm response might be used to keep lampreys out of certain streams, helping herd them into smaller and smaller waterways until they could be easily poisoned.

Researchers are now working to identify the specific chemical that acts as the repellant. They plan on doing tests in a stream this spring, using the chemical in tandem with lamprey sex pheromones, which attract the fish.

"You keep them out of areas that you can't treat well with our selective pesticides and get them to areas where you can really efficiently kill most of them," Siefkes says.

The finding is "very exciting," says Barbara Zielinski, a biologist at the University of Windsor in Canada. " The pheromones are promising as attractants — but the ability to repel lampreys is also extremely useful."

Testing the liquid from decaying lampreys isn't easy work, especially if the ventilation isn't good, says Siefkes. "But hopefully it's the smell of success."