Taking Measures to Control an Invasive Species

They are like something out of a nightmare.

Sea lampreys have a slimy, snake-like, 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 with the tooth-lined oral disc 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 non-mammalian 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."

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. King Henry I was said to have died in 1135 from eating a "surfeit of sea lampreys."

A bit more recently, in 2002, Great Lakes sea lampreys were flown to Queen Elizabeth II to make the traditional pie for her Golden Jubilee, since the creatures are now a protected species 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 anti-lamprey arsenal of government biologists.

But perhaps the strangest and most promising tactic in this battle 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 astronaut-like protective suits feed as many as 1,200 male sea lampreys per 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 a nest of infertile eggs.