RENEE MONTAGNE, HOST:
Researchers in the Great Lakes are trying to control an ancient fish, the sea lamprey. The species is notorious for latching onto other fish and literally sucking the life out of them. The lamprey larvae can be killed with a special poison, and now one biologist thinks he's found a way to make sure they're in the right place at the right time to die.
From member station WCMU, Amy Robinson reports.
AMY ROBINSON, BYLINE: Lamprey are, by most people's measure, ugly - eel-like, slippery with suction-cup mouths. Scientists say the animals can't see or hear very well. They're basically parasitic, swimming noses.
MICHAEL WAGNER: They rely more than any other animal, on just one sense: smell. They have this massive well-developed nose. That makes them prone to manipulation.
ROBINSON: Michael Wagner is a Michigan State University researcher and is trying to manipulate lamprey by tinkering with nature. In his home base, a biological station in Northern Michigan on the shores of Lake Huron, there are cement floors and large tanks writhing full of lamprey. Wagner says lamprey are attracted to the scent of their own larva and repelled by the scent of their dead brethren - really repelled.
TOM LUHRING: I was just going to load it half full.
ROBINSON: Researcher Tom Luhring puts a small amount of what's called alarm cue - essentially dead lamprey soup - into a tank of lamprey.
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ROBINSON: The lamprey go crazy. Some jump right out of the tank. Wagner plans to use this instinctive avoidance response to herd lamprey into streams, where their larvae can be killed more easily.
WAGNER: Think of the alarm cue as a stoplight that we're going to set to red. And the larval odor is a stoplight that we're going to set to green. So you hit this split in the river, you have the alarm cue on one side, the larval odor coming from the other side, you give the animal a very easy choice that's evolved to make. And that is; turn right. So you turn right, turn right, turn right again. Get them all aggregated into a few tributaries in this big watershed.
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ROBINSON: So now Michael Wagner is working in this watershed of more than 400 tributaries full of lamprey larva. He's taken an entire river system and turned it into a research lab. The work he's doing is all about pheromones.
Marc Gaden is with the Great Lakes Fishery Commission. He says this research could have international implications.
MARC GADEN: Around the world, scientists more and more are looking to these types of odors or pheromones in many different types of species, whether it's insects or fish. If this is used in the Great Lakes Basin to control sea lamprey, it'll be, to my knowledge, the largest ecosystem in the world where pheromone control is used to control an invasive pest.
ROBINSON: Gaden says lamprey all but destroyed the Great Lakes fishery before they were finally brought under control a half a century ago. Trout, salmon, whitefish, all either are killed or left with gaping wounds from the lamprey's feeding. A fishery that once produced 17 million pounds of fish annually crashed to only a few hundred thousand pounds.
The lamprey are at what's considered an acceptable level today, but they're always on the brink of a comeback. Wagner's work is aimed at keeping one step ahead of the fish.
WAGNER: You know the old phrase shooting fish in a barrel are easy? It's easy if you can get fish to swim into a barrel, which they're not very likely to do, right? You've got to put them there first. That's what we're doing. We're putting lamprey in a barrel.
ROBINSON: If his research works, Wagner's lamprey herding approach may be a benefit both those who want to control the lamprey and those who want to conserve them. In countries like Spain, Portugal, France, the U.K., lamprey are considered delicacies. Queen Elizabeth received a lamprey pie as part of her 60th Jubilee celebration. Since lamprey are protected there, it was imported from the Great Lakes.
For NPR News, I'm Amy Robinson.
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