Scientists target sex pheromones to control bloodsucking sea lamprey in Great Lakes

Great Lakes scientists are closer to using mate-attracting scents to help control the invasive sea lamprey.

For years, researchers have been studying pheromones — which either attract or repel the parasitic fish — as a method of luring sea lamprey into traps or streams not suitable for spawning.

Recently, a team of researchers developed a way of releasing the pheromones in the right places using a biodegradable substance that breaks down slowly in the water — a lot like those cleaning tablets for your toilet tank.

"We wanted to come up with a low-cost, low-maintenance method that would allow you to deliver that activation to the streams," said James Hanson, a chemistry professor at Seton Hall University.

Native to the Atlantic Ocean, sea lampreys made their way into the Great Lakes through shipping canals in the 1920s.

With almost unlimited spawning habitat and food supply and no natural predators, the lamprey devastated native fish like the lake trout.

Lamprey attach to other fish with a suction cup-like mouth filled with sharp teeth and a razor-like tongue. They feed on their prey's blood and bodily fluids, usually killing it.

Up to this point, control efforts have relied on a targeted pesticide that kills lamprey while they're still in the larvae stage, as well as barriers and traps, said Marc Gaden, communications director for the Great Lakes Fishery Commission.

The effort has been successful, reducing the sea lamprey population in the Great Lakes basin by 90 percent and restoring the fishery, he said.

However, scientists are looking to broaden their arsenal of weapons with a less toxic and more cost-effective alternative to pesticide. Their research has focused on pheromones released by male sea lampreys to attract females as they swim upstream to spawn.

Hanson said using the new technology, scientists can emit pheromones in places where males aren't likely to be because they aren't good streams for spawning. The females follow, but there's no one to mate with, he said.

"So they can't lay the hundreds of thousands of eggs they wanted to lay," Hanson said. "It will reduce the population of the sea lamprey by this sort of decoy approach."

Other odors that act as repellants could be used to steer lamprey toward traps or away from good spawning grounds, sort of a "push and pull effect," Gaden said.

"These odor cues that we're zeroing in on we think is the next frontier on lamprey control to supplement and really improve what we already do in the Great Lakes," he said.

Gaden said scientists are still a few years away from being ready to use pheromones as a control method in the field. He said pheromones likely will supplement, not replace, other control techniques.

"We need to do about 25 percent more lamprey control in the Great Lakes. They're that destructive," Gaden said. "Any tool we have in our tool chest that helps us achieve is something that's very welcomed and very important."

Hanson said the technology could be used in the fight against other invasive species in oceans, lakes or streams.

"Although we were developing it for the sea lamprey, there's other organisms that use pheromones or use other types of odor cues for parts of their life cycle," he said. "If they're invasive species, you could manipulate and try and control in that way."