Herding fish: 47,000 invasive Asian carp removed from Missouri lake

Ever tried herding fish?

Conservationists successfully used an experimental method to drive reviled Asian carp to one end of a Missouri lake so 47,000 of them, of about 119 tons, could be removed.

That's a lot of fish.

But the invasive species was crowding out sport fish like crappie in Creve Cour Lake near St. Louis. They were even leaping out of the water and striking people. The fish, which entered the lake when the Missouri River flooded a decade or so ago, had to be dealt with.

So the Missouri Department of Conservation teamed with the U.S. Geological Survey, the U.S. Fish and Wildlife Service and the St. Louis County parks department to try an experimental approach. It had been used in Asia but not in an integrated way in this country.

It's called the Unified Method and it uses a technique to drive the carp crazy.

"One of the things that get Asian carp really fired up is the sound of outboard motors," said fisheries management biologist Kevin Meneau, who coordinated the operation for the conservation department. "We were able to isolate that sound and broadcast it underwater."

They used the weapon to drive the carp out of sectors of the lake and then blocked them off with big nets. It took three weeks in the cold. But carp are more sluggish in the cold so they were easier to maneuver.

And native species of fish tend not to mind the motorboat noise so they were not driven to the nets.

Officials think they were successful in removing about 85 percent of the carp from the lake. They are not worried about the remaining fish again taking over because Asian carp require flowing waters, like the Missouri and Mississippi rivers, for their eggs to hatch. (All the carp rounded up were adults.) So the remaining population will eventually die out.

"The Unified Method was experimental, only components were used in other parts of the country," Meneau said in a conservation department announcement. "We brought it all together for this project and it was successful. We're going to spread the word to other conservation entities throughout the country that maybe this will work for them."

This story was originally published March 12, 2018 at 1:01 PM with the headline "Herding fish: 47,000 invasive Asian carp removed from Missouri lake."