Pheromones in river traps attract sea lampreys

By Jack Johnson

Scientists have found another promising weapon in the battle against sea lampreys, strong evidence that they may win the war against one of the Great Lakes’ most infamous invaders.

Researchers at Michigan State University have begun field tests on a chemical compound that tricks the lampreys and lures them into traps.

Weiming Li, an MSU fisheries and wildlife professor, led the 10-year research effort.

Li said a key discovery in the first half of the studies was that male lampreys release a pheromone that attracts females during mating. As a result, Li’s team identified the structure of the compound making up the pheromone.

Since then, Li said they discovered how to imitate the pheromone and use it to manipulate the lampreys’ behavior.

They’ve conducted tests on the Ocqueoc River between Rogers City and Cheboygan using the pheromone-laced traps.

Mike Siefkes, the sea lamprey program specialist for the Great Lakes Fishery Commission, said they are, on average, about twice as effective as the traps without it.

Sea lampreys are parasitic fish that resemble eels. Able to live in fresh and salt water, they made their way to the Great Lakes from the Atlantic Ocean in the 1920s through canals and locks that bypassed Niagara Falls. Before they were built, the alien fish couldn’t circumvent the falls.

Lampreys survive by latching onto other fish and eating away at them, which usually kills the host.

Marc Gaden, the communications director for the Great Lakes Fishery Commission in Ann Arbor, said lampreys nearly destroyed most of the game fish population in the Great Lakes by the 1950s.

Gaden said one lamprey can consume up to 40 pounds of fish in its lifetime. About 3 million inhabited the Great Lakes in the early 1950s.

Lampreys appeared to be taking over the entire ecosystem, but in 1957 researchers discovered the chemical TFM.

TFM, a lampricide, kills lamprey larvae in streams leading to the lakes. It has little effect on the rest of the ecosystem and is the main reason the population has dropped to about 450,000, according to Gaden.

Discovering TFM was a bi-national effort between the U.S. and Canada that funded testing of about 6,000 chemicals. Gaden said about 85 percent of the Fishery Commission’s budget now goes toward lamprey control.

The U.S. this year will spend about $10 million, $2 million more than the previous year, on research and control efforts, while Canada will spend about $8 million.

Referring to TFM as the “silver bullet” in lamprey control, Gaden said it’s the main reason why the $7 billion-a-year sport fishing industry in the Great Lakes has been revitalized.

Despite the success of TFM, Gaden said the number of lampreys in the Great Lakes is still too high, causing researchers to look for other options.

“We want to have another technique in our arsenal so we can attack this lamprey problem from as many angles as possible,” Gaden said, referring to the pheromone-trapping technique.

Li said the trapping method could lower use of the expensive lampricide.

Siefkes said this summer the commission is expanding testing of the new technique.

Ten Michigan streams will be fitted with the pheromone-laced traps this summer, four tributaries of Lake Superior, four of Lake Michigan and two of Lake Huron.

Rivers projected to get the traps feeding Lake Michigan are the Manistee, Little Manistee, and Betsie rivers and the Carp Lake Outlet. The rivers leading to Lake Superior will be the Misery, Rock, Miners and Betsy rivers. Also, the East Branch of the Au Gres and the St. Marys rivers on Lake Huron are scheduled for traps.

Ten more streams will be tested in Canada in 2010.

“After this summer, we’re going to have a really good idea of how effective this is going to be,” Siefkes. “We’re anticipating we’re going to have a really good effect on trap capture.”

Gaden said that, despite the latest promising research developments, the battle against lampreys must continue.

“They’re a resilient beast and they know how to survive. They’re older than the dinosaurs, and they haven’t changed much since then.”