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Trying to trap invasive sea lamprey with "eel ladders"

The sea lamprey is an invasive fish with a round mouth like a suction cup. It latches onto big fish like lake trout and salmon, drills its razor sharp tongue into them, and gets fat drinking their blood and body fluids. A single lamprey can kill up to 40 pounds of fish in its lifetime.

We spend about $20 million dollars a year to control lampreys. One of the main ways people do that is with a pesticide, but researchers are working on other ways to control the invasive species.

Michigan State University researchers are testing something called a sea lamprey ladder.

Michael Wagner is a sea lamprey expert and an associate professor in the Department of Fisheries and Wildlife at MSU.

He compares the ladder to a classic game: Plinko.

Credit Andrea Miehls / USGS
This ladder is part of a system designed to selectively filter out sea lamprey.

“It’s a board and studded with pegs. It’s put into the water at a steep angle - about 45 degrees - and it has water running over the surface of it. And eel-like fishes, like sea lamprey and American eels, can climb this ladder by pushing off against these pegs, where most other fishes can’t,” says Wagner.

The ladders are designed to control the flow of sea lamprey through dams. Wagner says the idea is to guide the lamprey to one side of the dam, using an “alarm cue” scent that sea lamprey release when facing a predator.

Wagner explains the ladder system this way:

“So imagine now that we have this fish ladder over on one side of the dam, and we’re pumping this alarm cue down it that the sea lamprey smell and they don’t want anything to do with going over there. And then on the other side of the dam, we installed these trapping devices with this ladder on it," he says. "So we guide the sea lamprey over there. They can go up this ladder and they get trapped. But any of the other fish that encounter it can’t go over it, and don’t get trapped.”

Wagner says they've had some success but they still have a ways to go.

"We’re very early in the research. This project that we started this year is the first attempt to try to prove the concepts underlying one of these selective fish passage devices,” he says.

Rebecca Williams is senior editor in the newsroom, where she edits stories and helps guide news coverage.
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