A speedy carp swimming in the Mississippi raises alarm bells to fight off invasive fish

This spring, an invasive silver carp blew up the Mississippi River — to the edge of where one researcher says the state has a chance to stop the species from advancing any further.

The fish, which has been flagged by the Minnesota Department of Natural Resources, took advantage of rising waters in May to sneak around locks and dams as the river swelled and drainage channels opened.

A DNR report released to environmental groups this week showed the fish traveled about 35 miles upstream, from La Crosse, Wisconsin, to north Winona, in less than one day.

Farther north, the tagged silver carp made the journey into the Mississippi, although some fish and other invasive carp species were caught downstream, said Grace Lubnaugh, DNR’s invasive fish consultant.

Advances in this carp’s flight mean it’s time to stop them at Lock and Dam 5, northwest of Winona, said Peter Sorensen, a professor at the University of Minnesota who has worked on the carp study. Sorensen’s own data showed invasive carp in the actual pond of this lock, with only a gate blocking further movement.

“It’s judgment day in a way,” he said.

According to Sorensen’s research, this lock is the most likely place where a fish deterrent will work, because there is no large spillway that carp can use to swim around the hull. Sorensen and a group of engineers developed one idea that could work there – a wall of bubbles and noise known as a “bio-acoustic fish fence” that runs through the lock tank and makes the carp back off.

But DNR hasn’t updated its carp plan in years and hasn’t evaluated Sorensen’s plan.

Loppnow said the agency needed time to invite people interested in the carp problem, and that it needed to evaluate a range of solutions, not just Sorensen’s idea.

The Stop Carp Alliance asked DNR to begin updating its plan for invasive fish in 2020, the same year that 51 silver carp and grass carp were pulled from waters near La Crosse.

Christine Goepfert, co-chair of the coalition and co-director of the National Park Conservation Society, said the progress of the silver-tagged carp should inspire the state to act.

“It’s like sounding the alarm,” she said. “It is time to move forward.”

Silver carp is one of four invasive species found in the Mississippi River and its tributaries. All these fish can destroy the ecosystem of the river. Sorensen said the silver carp is an excellent jumper and is able to lift up to 9 feet out of the water.

The fish grows to 40 pounds and has been known to hurt boats on the water.

“If they hit you in 6 feet of water, flat in your jaw, they break your jaw,” Sorensen said.

The progress of this and other invasive carp species is such a threat to the river that it was the main reason for the St. Anthony’s top boat lock to be permanently closed in Minneapolis in 2015.

Guepfert said that was an effective massif for the upper river, but said there was no real protection now for the waters downstream. This includes not only the Mississippi River, but Lake Pepin, the Saint Croix River, and the Minnesota River.

Time is of the essence for another reason, according to Colin O’Connor Toperman, director of the Land Use and Planning Program at Friends of the Mississippi River.

She said if the DNR is able to move quickly and determine next steps, the agency can request funding for a Lock and Dam 5 barrier this fall and possibly get it in the state budget. But if the deadline is missed, Minnesota’s biennial budget means there won’t be another chance for two years.

Currently, an engineering report submitted by Sorensen on his proposal pegs the cost between $8.25 million and $16.5 million.

According to the DNR Report on Rogue Carp, there is no evidence of fish breeding in Minnesota waters. That doesn’t mean that doesn’t happen — carp eggs are small and hard to find in the long stretches of river between each dam, Sorensen said.

Loppnow said that DNR will move some of its larval samples upriver to the area where the tagged carp was tracked, and begin trying to fish there as well.

“We need to get out there and do some sampling, and unfortunately with the water level rising, it’s not safe to get out there and net now,” Lubno said.

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