Poison Larvae of Sea Lamprey

Federal wildlife workers will go after one of the Great Lakes’ greatest invasive pests this week when they poison the larvae of sea lamprey in a stream feeding Lake Michigan.

The U.S. Fish and Wildlife Service plans treatments for Tuesday through next Sunday in the Mitchell Creek stream bottom. The creek flows through Traverse City State Park before entering Grand Traverse Bay’s east arm. The park is in Grand Traverse County’s East Bay Township, east of Traverse City.


“The larval sea lamprey in these rivers is at its most vulnerable life stage,” said Alex Gonzalez, a fish biologist with the U.S. Fish and Wildlife Service’s Ludington office. “For us to get the adult lamprey in the lakes would be impossible.”


The treatments are 95 percent to 99 percent effective in killing the parasite at this stage, Gonzalez told the Traverse City Record-Eagle.

Lamprey have been sucking the blood from lake trout, salmon and walleye for decades.

Gonzalez said the lamprey control program has helped control the parasite’s Great Lakes populations for 50 years and keep native fish populations viable. Treatments are typically done every 3 to 5 years, he said.

Heather Hettinger, a fisheries biologist with the Michigan Department of Natural Resources, said most local waterways that connect with Lake Michigan — such as the Betise and Platte rivers — have been regularly treated for sea lamprey for decades.

The lampricides don’t pose an unreasonable risk to humans or the larger environment, but people are encouraged to limit their exposure as the treatments are underway, Hettinger said. She said the chemicals biodegrade quickly.

Adult sea lampreys, which reach lengths of 2 to 3 feet, resemble eels but behave more like leeches. With round, disk-like mouths and sharp teeth, they latch onto fish and suck out their blood and other bodily fluids, killing or severely weakening the hosts.

Although native to the Atlantic, they can live in fresh water and migrated to the Great Lakes through shipping canals. By the late 1940s, the prolific invaders had decimated trout, whitefish and other sport and commercial species across the lakes.

The fight against lamprey has cost more than $400 million over five decades. The lamprey population has dropped by about 90 percent since researchers perfected a way in the late 1950s to kill lamprey but not other species.