Keeping sea lamprey in check allowing lake trout to rebound in Great Lakes

Still, according to one official, more lake trout are killed by sea lamprey predation in Lake Superior than sport and commercial fishing combined.

DULUTH, Minn. — Scientists have found a way to keep sea lampreys largely in check in the Great Lakes, which has allowed the lake trout population to rebound.

The sea lamprey is an invasive species that has needle-sharp teeth that can bore a hole through fish scales, Minnesota Public Radio reported. The lampreys can then suck out blood and fluids.

“It’s caused tremendous damage,” said Doug Jensen, Aquatic Invasive Species Program Coordinator at Minnesota Sea Grant. “It’s called the ‘Vampire of the Great Lakes’ for good reason. It made lake trout go extinct in all the Great Lakes except for Lake Superior.”

Scientists created a chemical called TFM in the 1950s that kills sea lamprey when they’re still small larvae. The Great Lakes Fishery Commission treats about 200 rivers around the Great Lakes with the chemical. Other control efforts include barriers that are built across streams to prevent lamprey for getting to spawning areas.

State fisheries managers recently ended a trout stocking program in Lake Superior because hatchery-raised fish are no longer necessary to increase the population. Officials also opened a small commercial lake trout fishing season near Duluth this year.

“It’s kind of a culmination of 50 to 60-plus years of rehabilitation coming full circle,” said Cory Goldsworthy, Lake Superior Area Fisheries Manager for the Minnesota DNR.

While lamprey numbers are stable in lakes Michigan, Huron and Ontario, they have increased in lakes Superior and Erie, according to a commission report.

“There’s still more lake trout killed by sea lamprey predation in Lake Superior than sport and commercial fishing combined,” Jensen said.

The growth may be due to warmer water temperatures and the increase in trout, which means lampreys have more prey to feed on, commission officials said.

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