JANESVILLE — Invasive carp trying to reach the Le Sueur River will be in for quite the shock once the Department of Natural Resources completes electric barriers on two area waterways.

The structures are slated for completion near Eagle Lake and Janesville within the next two months. They're meant to stem any mass movement of multiple Asian carp species into Madison Lake and Lake Elysian.

Invasive carp are adept at swimming upstream into new habitats, and once they arrive they can wreak havoc on water quality and the food chain.

If left unimpeded, DNR officials suspect the carp could make their way from the Minnesota River, to the Blue Earth River, to the Le Sueur River, from which they'd be able to reach dozens of lakes including Madison and Elysian.

“Given the importance of those lakes to this area, especially Madison Lake, we felt it was important to protect them from invasive carp,” said Craig Soupir, the DNR's Waterville area fisheries supervisor.

Common carp are already prominent nuisances in southern Minnesota waterways, but the electric "wall" is meant to prevent bighead, grass and silver carp — known for its jumping ability — from joining the fray. Bighead and grass carp have already been documented in the Minnesota River in recent years. Soupir said any unknown populations of them already in the Le Sueur River are minor.

“If one or two get in it’s not a big deal,” he said. “It’s more mass migration of thousands of them that can cause lots of problems.”

The barriers will act as an electric fence keeping mass migrations of carp downstream. Electric currents running through concrete aprons immobilize the fish, causing the current to push them back where they swam from.

Signs and fencing will ward people away from the barrier. Canoers or kayakers wouldn't be in danger as long as they keep their hands out of the water.

Construction began on the first barrier in Mayhew Creek on 631st Avenue near Janesville within the past two weeks. The waterway is an outlet of Lake Elysian. The second site, southeast of Eagle Lake on a creek outlet of Madison Lake, should begin this week. The projects total between $1.5 million and $1.7 million, with the funding coming from the 2008 Clean Water, Land and Legacy Amendment. 

Windom has had a similar barrier in place for years, which Soupir said has been effective. One was installed in northwest Iowa more recently after carp were found in a popular chain of lakes.

Bighead, grass and silver carp cause a myriad of problems for native fish species. As planktivores, they compete for the same food sources as popular game fish like walleye. Especially on popular fishing holes like Madison Lake, their arrival spawns serious complications.

John Stephanie, past president and current treasurer of the Lake Elysian Watershed Association, is familiar with the problems common carp brought to the lake. He said one summer the carp died off and washed up on his and other's shorelines. 

“We had about probably 40 to 50 carp over the two-week period dead," he said.

He welcomed the DNR's project, saying he was hopeful it’ll prevent more carp from establishing a habitat on Lake Elysian. 

“I imagine if you could keep those out it would be great,” he said.

Paul Baer, chair of the Madison Lake Watershed and Lake Association, said his group has been interested in the barrier project over the last couple years. He's also chair of the LeRay Township Board, where the barrier near Eagle Lake will be installed.

From his property on the Madison Lake, he can see the outlet where any invasive carp would come from.

"Down the road they could show up tomorrow, so it’s good they’re proactively putting this in," he said.

Including Madison Lake and Lake Elysian, the barriers could protect 31 lakes and 142 miles of rivers, stream and ditches, according to the DNR. The project’s origin dates back to a statewide, 2012 assessment measuring Asian carp’s potential to migrate upstream.

The areas where the barriers are being installed are marked by deep red on the map, indicating the fish’s movement wouldn’t have been impeded in the past. The Rapidan Dam has long been considered the closest year-round barrier in the region.

Once completed in late October or early November, the region will have two additional barriers. For carp, Soupir said it'll mean a much more difficult journey to spread into the Le Sueur River.

“It’s always best to prevent them, because once you’ve got them you have to manage them,” he said.

Follow Brian Arola @BrianArolaMFP.

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