The next phase of the decades-long fight against destructive sea lamprey in the Great Lakes was expected to begin Monday when researchers were to pump a man-made love potion into more streams after experiments from last spring showed it helped lure the lamprey into traps.
The potent lamprey aroma -- a scent males emit from their gills -- worked so well, it drew both males and females into traps, a surprise. Now the unromantic-sounding 3-kPZS is being tested to see if lamprey can be drawn out of Lake Superior into two targeted streams, where it will be easier to kill them.
But the battle scientists have waged against the sea lamprey since the 1950s is a cautionary tale for anyone who thinks Asian carp easily could be controlled if they colonized the Great Lakes. This newest weapon against lamprey has taken three decades to develop.
Sexual scents, or pheromones, have been used to control insects, but not for fish or other animals until now, said Michigan researcher Nick Johnson. Scientists need three years of testing before determining how successful the potion will be at controlling the lamprey.
Lamprey are vampire-like parasites that suck the life out of fish. One lamprey can kill 50 pounds of fish in less than two years.
Lamprey love potion has taken decades
In a heavy snowstorm last week in the Upper Peninsula, Johnson was out in the field at two aptly named streams: the Misery and Rock rivers.
Johnson, a research ecologist with the Hammond Bay Biological Station in Michigan, was setting up equipment for a new chapter in the 50-year-old battle between humans and sea lamprey, an invasive species that reached the Great Lakes in the 1920s.
A new experiment that was to start Monday will show whether scientists can use a man-made copy of a lamprey love potion to lure the creatures out of Lake Superior and into the rivers. If so, it could be a big leap forward in controlling lamprey behavior.
The lamprey, which attack fish such as lake trout and whitefish and feed on their blood and guts, decimated native fish populations in the 1950s. A poison, TFM, was developed in 1958 to kill the eel-like creatures while they are still babies in streams. But it's expensive and doesn't work on adults.
At last, the right bait
Scientists have spent decades working to identify, copy and patent a lamprey love potion, called 3-kPZS, so they could lure adult lampreys into traps. They made it work in lab experiments; now they're making sure it works in nature.
So far, it does. The seductive scent, or pheromone, produced by male lampreys draws lusty females from miles away toward the males' nests in streams. In their first field experiment last year, scientists were able to capture 30% more lampreys in traps baited with 3-kPZS than in traps without it.
The pheromones were used last year in 10 Michigan streams and this year, the love potion will be pumped into the same state streams plus 10 in Canada during mating season to test it.
But last year's results brought a surprise -- the scent drew male lamprey, too. It's possible that 3-kPZS is a pheromone that makes lampreys come together rather than a mating scent, Johnson said. That's even better news. "It means we can target both sexes" with the pheromone, he said.
Now that scientists know 3-kPZS works like a charm within a stream to draw lampreys to a trap, they're trying it to see if they can lure the lampreys from Lake Superior into a targeted stream with the love potion.
Starting this week and for the next three months, crews will dose the Misery and Rock rivers with the pheromone 24 hours a day, seven days a week. If it works, lamprey will be drawn into the rivers and then stopped by existing barriers and traps, so they can't mate.
Sea lamprey are born and spend their youth in streams, then move into the Great Lakes as adults to feed. They attach to native fish's soft flesh and suck out their innards, killing them. One sea lamprey can kill 50 pounds of fish in less than two years.
They return to tributaries of the Great Lakes to spawn.
"We have to use every weapon we can against the lamprey," Johnson said. "There is no silver bullet."
The St. Marys River in the Upper Peninsula is too big to use poison in, so it's been especially difficult to control lamprey there and in neighboring Lake Huron, he said.
Researchers need three years of data to make sure the pheromone works and isn't harmful to the environment. This is the second year. After that, the scientists can apply to the U.S. Environmental Protection Agency to register 3-kPZS, making it the first pheromone certified beyond the insect world.
Carp project just starting
Researchers elsewhere hope these results signal hope for controlling other invasive species. Experts have mentioned pheromones as a possible Asian carp control. The enormous fish probably have invaded Lake Michigan and could out-compete the Great Lakes' native species and endanger boaters and anglers because of their habit of leaping out of the water.
But identifying, copying and testing pheromones for a species is a long process, if it can even be done. Johnson said scientists started working on the lamprey pheromone around 1980. Work on Asian carp pheromones is still in the early stages, he said.
Mike Siefkes, sea lamprey program specialist with the Great Lakes Fishery Commission, helped identify 3-kPZS as a graduate student at Michigan State University. "It was tedious," he said.
Scientists also tried bubbles, lights and weird noises to keep sea lamprey out of streams -- methods also mentioned to control Asian carp -- but those didn't work, he said.
After more than 50 years trying to control them, sea lamprey still wound too many fish in all the Great Lakes except Ontario and are not under control in Lake Huron. About 100 employees in the U.S. and Canada work on lamprey control, at a cost of millions of dollars each year, Siefkes said.
But pheromones provide new hope. Scientists are working to find more lamprey pheromones. Adding those to 3-kPZS could make it an even more potent cocktail.
"If these could work in a river like the St. Marys, it would be huge," Siefkes said. "We're encouraged."
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