East Lansing, MI ... The patented pheromone has been more than a decade in the making. It's a copy of a scent male sea lampreys, a highly destructive invasive species, send out into streams during mating season to draw females to their nests.Although scientists have copied and used pheromones in the insect world for pest control, no one has ever tried it on fish or any other vertebrates before, said research ecologist Nick Johnson of the Hammond Bay Biological Station in the Upper Peninsula.Starting nearly two weeks ago and continuing most nights through June, Johnson and helpers are testing the love scent by pumping small doses of the pheromone through existing traps into specific rivers in northern Michigan.Lampreys are born in these streams and return to mate. Johnson's earlier research, while he was a student at Michigan State University, where the pheromone was developed, showed that females will swim upstream long distances hunting for the pheromone's source, straight into traps."Once they smell it, they follow it," Johnson said.Researchers check the traps every day or two to see how many lampreys they have lured. After warm spring nights, when mating lampreys are most active, Johnson expects to find as many as 500 lampreys in a trap. Once trapped, the females are destroyed or used in research. They won't produce any offspring, and that's key."To control the population, we want to remove the females," Johnson said.Unchanged creatureSea lampreys, a species that has survived nearly unchanged for 400 million to 500 million years, are native to the Atlantic Ocean. Scientists believe the lampreys migrated into the Great Lakes after locks and canals bypassing Niagara Falls were built. Since they have no predators in the Great Lakes, once established, they flourished.The lampreys prey on soft-fleshed native fish like lake trout and whitefish, attaching sucker mouths to their sides and feeding on their bodily fluids. The fish usually die.(2 of 2)After lampreys showed up in Lake Huron in the 1920s, they spread throughout the upper Great Lakes, devastating various fish species, including lake trout, by the 1950s. Since those fish were predators of invasive alewives, their loss led to an explosion of alewives.Since 1958, the main weapon against lampreys has been a chemical compound known as TFM, which kills the slippery fish when they're still young larvae in streams. It is safe for other species but expensive. The Great Lakes Fishery Commission, created in 1955 mainly to control sea lampreys, spends most of its $18-million budget on the lampricide program, said Mike Siefkes, sea lamprey specialist for the commission.Lampricide is hard to use on large rivers like the St. Mary's River in the Upper Peninsula, which leads into Lake Huron. The Hammond Bay Biological Station traps male lampreys in that river, sterilizes them with a chemical compound and releases them to mate with fertile females. Males and females die after they mate, so the lamprey couple will not reproduce.Barriers usedTFM, barriers that halt their movement and sterilization have brought lamprey numbers down to 10 percent of their peak of five million decades ago, Siefkes said. "But we need to keep on it, or they'll bounce back," he said. There still are too many lampreys in lakes Michigan and Huron, although the population is better controlled in Lake Superior and native fish are returning there, he said.Into smaller riversIf the love potion works, the traps could catch large numbers of lampreys.The pheromone also might be used to lure spawning lampreys out of rivers too large to treat with lampricide and into smaller rivers where the chemical can work, said Johnson."There are lots of strategies we could use," Johnson said.The pheromone is so potent that only miniscule amounts are needed, so it could be a cheaper alternative to lampricides, Johnson said.For now, all the research on pheromones is being done in Michigan. Besides 3-kPZS, MSU has ongoing research on other pheromones, including one that young lampreys emit into streams as larvae. That pheromone tells adults which streams to return to later to spawn.If the pheromones work in the wild, it could be a groundbreaking step, not just for lamprey control but other invasive species, Siefkes said.
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