The double life of the blood-sucking sea lamprey

Michigan State University has several labs dedicated to the study and control of lampreys, which leads to idiosyncratic subjects. Lamprey skeletons are made of cartilage rather than bone and are capable of regenerating a fully functional spinal cord even after cutting it in half. They possess incredible olfactory power, capable of detecting odors at extremely low concentrations—equivalent to being able to locate a few grains of salt in an Olympic-size swimming pool, according to Anne Scott, an MSU professor. Native populations live in salt water, then swim to inland tributaries to reproduce and die, like a parasitic salmon. Lamprey species have lived on Earth for hundreds of millions of years; They predate the dinosaurs and have survived at least four mass extinctions.

These unique adaptive abilities have earned the sea lamprey grudging admiration from conservationists tasked with eradicating them. “There’s no denying that an invasive species can destroy the environment,” says Griffin. “But you have to have respect for an animal that has lasted so long.”

sometime in 19th century, Petromyzon marinus meandered first from the North Atlantic into Lake Ontario. At its southeastern edge, Niagara Falls’ rushing 3,100-foot span provided a natural barrier preventing the species from further westward spread, but the deepening of the man-made Welland Canal provided an alternative route of entry. In the larger Great Lakes, sea lampreys encountered a buffet of trout, sturgeon, whitefish, walleye, catfish and other native water species. The lampreys latched onto, bored into, and sucked off the blood and bodily fluids of millions of fish — injuring and killing scores. There were few, if any, predators to prevent their spread.

As the problem worsened, people began to feel her presence. In the mid-1940s, about four out of five commercially caught fish in the northern portions of Lakes Huron and Michigan were too badly injured by lampreys to sell. Lake Michigan’s stretch of Lake Michigan alone caught 6.5 million pounds worth of lake trout in 1944, but less than five years later only 11,000 pounds were caught in the entire lake. Badly hit by lampreys, overfishing and pollution, the local fisheries lost tens of millions of dollars a year until the 1960s. In 1949, commercial fishermen testified before Congress that their industry was “doomed.” Fishermen and local residents shied away from the blood-slurping parasite. “People thought they were like horrible creatures from the bottom of the earth,” said a woman whose family owned a sport-fishing resort near Duluth Great Lakes Sea Lamprey: The 70 Year War Against a Biological Invader.

In the early days of the invasion, wildlife managers and local residents fought the sea lamprey with everything they could think of. From landing nets to javelins, few weapons have gone untested. Conservationists built simple metal barriers to prevent migratory adults from reaching their spawning grounds and tapped larvae with newly invented electrofishing devices. At one dam, operators constructed a metal ramp to create a booby trap that led lampreys over the dam’s edge and into a bucket of oil. A conservation officer named Marvin Norton led pitchfork-armed sports clubs on field trips to hunt and spear the lamprey. Every attempt failed. “I suspect that from now on the lamprey will be with us like fleas on a dog,” said Gerald Cooper of the Michigan Department of Conservation in 1954.

At what is now the US Geological Survey’s Hammond Bay Biological Station, scientists worked to find a chemical solution. In 1956 they finally got lucky with the 5.209. tested formula: 3-trifluoromethyl-4-nitrophenol or TFM. To the researchers’ delight, TFM was able to eradicate lamprey larvae while sparing most native biota. Two years later, this novel lampricide was pumped into Michigan’s Mosquito River.

Within 20 years, TFM proved to be a formidable weapon. It was particularly effective in conjunction with the numerous levees in the region, which blocked more than half of the sea lamprey’s potential spawning habitat. By 1978, the number of spawning sea lampreys in Lake Superior had declined by 92 percent. Across the Great Lakes as a whole, the lamprey population has declined from 2 million at its peak in the 1950s to a few hundred thousand today.

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