U scientists see better lamprey trap

[eric myers 2]

Last update: October 3, 2005 at 7:23 AM
U scientists see better lamprey trap
Tom Meersman 
Star Tribune 
Published October 3, 2005 

University of Minnesota scientists have discovered a new and better way to reduce sea lampreys in the Great Lakes: using a chemical signal that can trick the voracious predators into traps.

The lampreys invaded the lakes and their tributaries, decimating lake trout, whitefish and other fish populations by the mid-20th century. To protect the remaining populations of large fish, fisheries managers have for years applied chemicals to streams to kill juvenile lampreys before they migrate to the lakes.

Peter Sorensen, professor of fisheries, wildlife and conservation biology, said that he and a team of researchers identified and synthesized a chemical, known as a pheromone, that is emitted by juvenile lampreys in streams to attract the adults for spawning.

The research, published Sunday in November's issue of Nature Chemical Biology, is the first migratory attractant to be identified in any fish. Sorensen said that salmon and other fish also use odors to navigate.

The synthetic form of the lamprey pheromone can attract the adults to places where they could be captured -- and then killed or sterilized, he said. The attractant also could be used on streams blocked by small dams where the lampreys could not spawn, he said.

In laboratory tests, scientists offered lampreys two water channels -- one with the pheromone and one without. Lampreys greatly preferred the one with the pheromone. Tests in streams may begin next year, and researchers hope the attractant will be in wide use by the end of the decade.

Sorensen, who has been studying sea lampreys for 16 years, collected the lamprey pheromone and worked with chemists to identify its three major components, including a natural steroid. Thomas Hoye, a university chemistry professor who also worked on the project, isolated and synthesized the steroid, proving that it could be manufactured.

"This is an entirely new and very appealing, environmentally safe and hopefully inexpensive way to control lamprey," Sorensen said. If the pheromone can replace the chemicals now used, he said, it would avoid the expense of transporting truckloads of lampricides to remote streams and the crews of people needed to apply and monitor them. The U.S. and Canadian governments spent $16 million last year to control sea lampreys, much of it on the lampricide treatment program.

Using pheromones also has the advantage of affecting only lampreys, Sorensen said. The lampricides can accidentally kill other aquatic life in streams.

The research was supported by the university's Agricultural Experiment Station, the National Institutes of Health and the Great Lakes Fishery Commission, which is responsible for controlling lampreys in the Great Lakes.

Hoye, the chemist, said that it will take two or three years to refine the process by which the pheromone is synthesized and to make it more affordable. The olfactory sense of the lampreys is so sensitive that in some cases it takes only a few grains of pheromone to treat a stream, he said.

Sorensen is also studying pheromones of common carp, including sex pheromones that help fish to find one another to mate. He said that identifying these natural chemicals in fish could offer a "ray of hope" in the long term to help control populations of other invasive species such as Asian carp.