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Old Foe Attacked With New Weapons

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By KARI LYDERSEN, The Washington Post

Published: September 28, 2007

They are like something out of a nightmare.
Sea lampreys have a slimy, snakelike, muscular body capped by a suction-cup mouth ringed in teeth - along with a sharp probing tongue and a primal urge to suck blood.

They clamp onto the sides of fish and rasp through scales and skin with their tongue, traveling with the fish and sucking its blood until it's nearly dead. In Lake Ontario and other freshwater bodies, that has made lampreys a scourge, one the government spends millions to control.

Along with hagfish, sea lampreys are considered the most primitive vertebrate still living. The sea lamprey was one of nine nonmammalian organisms chosen for genetic sequencing, along with slime mold and roundworms, by the National Human Genome Research Institute to identify benchmarks on the evolutionary timeline.

'They are essentially a living fossil,' said Marianne Bronner-Fraser, a California Institute of Technology biology professor involved in the project. 'They look just like the vertebrates that emerged on the evolutionary tree hundreds of millions of years ago.'

Suiting Up For Battle

Native to the Atlantic Ocean and East Coast rivers where they spawn, sea lampreys, especially baked in pies, have long been a royal delicacy in England.

They were found in Lake Ontario as far back as the 1800s, but they invaded the rest of the Great Lakes in the early 1900s, probably through ballast or attached to the sides of oceangoing ships. Now, the government spends $14 million each year trying to control the primitive pests, and fisheries officials say more money is needed.

Chemicals, traps and electric barriers in streams are among the weapons in the lamprey arsenal of government biologists.

Perhaps the strangest and most promising tactic in this battle, though, is a ritual that smacks of science fiction and is carried out every summer in a U.S. Geological Survey research station in Millersburg, Mich., on the shores of Lake Huron.

There, workers wearing astronautlike protective suits feed as many as 1,200 male sea lampreys a day into a machine that gives them an automatically calibrated shot of chemicals to render them sterile.

The sterile males are then released into the St. Mary's River spawning area, where they compete with fertile males for mates. A female that mates with a sterile male will lay infertile eggs.

At their peak in the 1960s, sea lampreys wiped out much of the sport and commercial fishing in the Great Lakes. 'All the fish being stocked were coming out like Swiss cheese, with lamprey wounds,' said Great Lakes Fishery Commission spokesman Marc Gaden. 'It's not an exaggeration to say sea lampreys changed a way of life in the Great Lakes - communities that relied on commercial fishing and people who liked sport-fishing - the entire food web was altered.'

Fighting The Invaders

Since then, chemicals called lampricides and electric barriers in the streams where lampreys spawn have cut the Great Lakes sea lamprey population from almost 3 million to about 433,000. But electric barriers and widespread lampricide use are not possible in the St. Mary's River, a broad, navigable waterway connecting Lake Superior and Lake Huron, which Gaden calls 'the motherlode of sea lamprey spawning.'

'Lampreys were building up there like an invading army going out into Lake Huron and knocking the stuffing out of the fish,' Gaden said. 'The sterilization program was the linchpin to getting them under control.'

Sterilization of males, often through radiation, is used to control other pests, including mosquitoes, flies and rats. In larger animals, including possums and deer, females have been sterilized for population control.

Gaden said boll weevil sterilization was the inspiration for the sea lamprey program, which started in 1991. He knows of no other aquatic sterilization program of a similar scale.

Gaden noted that out of about 180 invasive species currently inhabiting the Great Lakes, sea lampreys are the only ones that can be effectively controlled.

'It takes ongoing work and continued vigilance,' he said. 'But we can do it.'

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