This spring, an invasive silver carp swam up the Mississippi River — just to the edge of where a researcher says the state has a chance to stop the species from advancing further.
The fish, tagged by the Minnesota Department of Natural Resources, took advantage of high water in May to bypass locks and dams as the river swelled and weirs opened.
A DNR report released this week by environmental groups showed the fish traveled about 35 miles against the current, from La Crosse, Wisconsin, just north of Winona, in less than a day.
It’s the farthest north a tagged silver carp has traveled the Mississippi, though some fish and other invasive carp species have been caught upstream, said Grace Loppnow, an invasive fish consultant with MNR.
The progress of this carp’s journey means it’s time to lock them up at Lock and Dam 5, just northwest of Winona, said Peter Sorensen, a University of Minnesota professor who has made a career out of the study. carp. Sorensen’s own data showed invasive carp in the actual basin of this lock, with only one gate preventing further movement.
“It’s judgment day, in a way,” he said.
According to Sorensen’s research, this lock is the most likely place a fish deterrent would work, as there is no large weir that carp could use to swim around the structure. Sorensen and a group of engineers have developed an idea that could work there – a wall of bubbles and noise known as a “bioacoustic fish fence” that would span the lock basin and drive carp back.
But the DNR hasn’t updated its carp plan in years, nor has it evaluated Sorensen’s plan.
Loppnow said the agency needed time to bring together people interested in the carp problem and needed to evaluate a range of solutions, not just Sorensen’s idea.
Meanwhile, a group of advocacy organizations by the name of Stop Carp Coalition has called on MNR to begin updating its invasive fish plan in 2020, the same year 51 silver and grass carp were removed from the waters near La Crosse.
Christine Goepfert, co-chair of the coalition, said the advance of the tagged silver carp has created an urgent moment, which should inspire the state to act quickly.
“It’s like sounding the alarm,” she said. “It’s time to move on.”
The silver carp is one of four invasive carp species that have been found in the Mississippi River and its tributaries. All these fish can destroy the river ecosystem. Silver carp distinguish themselves by being excellent jumpers, capable of casting up to nine feet out of the water, Sorensen said.
The fish reach 40 pounds and have been known to injure boaters on the water.
“If they hit you 6 feet out of the water, flat in your jaw, they break your jaw,” Sorensen said.
The advance of these and other invasive carp is such a threat to the river that they were the main reason for the permanent closure of Upper St. Anthony Lock in Minneapolis in 2015.
Goepfert said it was an effective blockage for the upper reaches of the river, but said there was no longer any real protection for the waters downstream. This includes not only the Mississippi, but also Lake Pepin, the St. Croix River, and the Minnesota River.
Time is running out for another reason, according to Colleen O’Connor Toberman, director of the Friends of the Mississippi River land use planning and development program.
If the DNR is able to act quickly and identify next steps, the agency could apply for funding for a barrier at Lock and Dam 5 this fall and potentially enter the state budget, a she declared. But if that deadline isn’t met, Minnesota’s two-year budget means there won’t be another opportunity for two years.
Currently, an engineering report Sorensen provided on his proposal pegs the cost at between $8.25 million and $16.5 million.
According to the MNR’s Rogue Carp report, there is no evidence the fish bred in Minnesota waters. But that doesn’t mean it doesn’t happen, Sorensen said — carp eggs are tiny and hard to find in the long stretches of river between each dam.
Loppnow said MNR will move some of its larval sampling upriver to the area where the tagged carp were tracked, and also begin trying to catch fish there.
“We have to go out there and do some sampling, and unfortunately with the high waters, it’s not safe to go out there and fish right now,” Loppnow said.