Minnesota DNR rolls out action plan to prevent the spread of invasive carp

Removing invasive carp

Removing invasive carp

It’s a mesmerizing sight: a school of invasive carp, leaping from the surface of the Mississippi River.

“They grow up to be 45 pounds,” says Peter Sorenson, a University of Minnesota biologist. “Jump nine to ten feet in the air, and they break people’s bones. They strip the ecosystem of all its food, they’re basically vacuum cleaners. They make life on the river unenjoyable.”   

“All of these fish are voracious eaters, they really outcompete our native fish,” adds Colleen O’Connor Toberman, Land Use and Planning Director with Friends of the Mississippi River. “They will all damage the fishery. There are places downstream where carp are fifty percent of the fish in the river.”  

Experts say the aggressive species has been moving upstream for decades, including hundreds outside Winona.

Some are caught as far north as the Twin Cities.

“We are seeing more invasive carp in Minnesota in the past year than we’ve ever seen before,” Toberman explains. “Further upstream on the river then we’ve ever seen them before.”

On Thursday, the DNR updated its action plan to prevent their spread.

“We will be taking every action we can to reduce populations,” says Heidi Wolf, in charge of ecosystem management and prevention at the agency. “Keep numbers as low as possible in the state of Minnesota, while exploring other options.”

In its new report, the DNR says it’s contracting with commercial fishers to tag and remove carp- and is tracking data to determine size, age, reproductive status, and spawning areas of the species.  

“It’s essential that we start to act immediately,” Sorenson declares. “These fish reproduce in an explosive fashion, with a million eggs per female. They’re hundreds of them present. It could happen anytime.”

But the DNR plan calls for more study over the next four years before installing deterrent technology to block carp from moving upriver.

One being looked at is a bio-acoustic fish fence, or BAFF, which is now used in Kentucky.  

“So, it uses sound, light, and bubbles in a lock chamber that carp don’t like to swim through,” Toberman says. “Native fish actually don’t seem to be as deterred by them as carp do, so it’s a fairly targeted intervention.”  

Another device is called an acoustic deterrence system, that emits sounds that repel carp, but don’t affect native fish.

“They only use a sound at a frequency that our native fish in Minnesota can’t even hear,” Toberman notes. “So, our native fish don’t even know that the sound is being played, and carp really hate it.”

Bio-systems could cost up to $15 million to install in Minnesota, according to the DNR.

 A U.S. government study says use of these devices cut the number of carp trying to get through in half.

“We’ve also gained a lot in terms of technology and methodology on evasive carp capture,” Wolf told reporters. “We’ve gained the ability to tag and track invasive carp in the water, which has changed the way we capture and remove carp.”

The DNR says installing deterrents will be a collaborative process with the U.S. Army Corps of Engineers, which owns locks and dams on the river, and other agencies.

“We’re looking for final information from the U.S. Army Corps on what they need for the next step,” Wolf says. “We have some clarity about what permits would be needed, including a realty permit, needed to use the property, also several levels of environmental review, which may be even more challenging.”  

Sorenson agrees that more study would be valuable- but he says the state needs to act now.

“In four to five years, these fish moved from Iowa into Minnesota waters,” he says. “If it takes four to five years to put a deterrent in place, which we’re calling for, then it’s too late.”