The U.S. Army Corps of Engineers has adjusted the gates at Lock and Dam 8 on the Mississippi River near the Iowa border to stop the spread of Asian carp, using advice from experts from the University of Minnesota.
The lock and dam is the only one on the Mississippi to be adjusted to fend off the invasive species to date, the corps said in an announcement Wednesday morning.
University of Minnesota Prof. Peter Sorensen, an expert on Asian carp who is advising the corps, said the changes "are a big deal," altering water flow at the dam in a way that prevents carp from passing upriver.
Sorensen and his team have been working with the corps for several years, and adjustments have been tested, studied and retested. Wednesday's announcement is "a very important step," he said, the first case of the agency officially adopting such an operational change at one of its lock and dams to fight invasive species.
"I think it is kind of extraordinary, where someone has actually done something proactively, voluntarily because it's the right thing to do," he said. "I hope it will set a precedent, and I think it will make quite a difference."
Sorensen said the goal of the changes is to reduce the movement of carp "to just a few percent of present levels, which already appear to be low." He said the changes could likely reduce the carps' passage by 50 percent.
In June, state officials reported the largest invasive carp ever captured in Minnesota — a bighead weighing more than 61 pounds caught on the Minnesota River near Redwood Falls. Sorensen said at the time that he believes the state can take measures to keep invasive carp downstream and that the main threat remains along the Mississippi's lock and dam system.
The Upper St. Anthony Falls lock on the Mississippi River in Minneapolis was closed two years ago, in part to deter the carp's migration.
Lock and Dam 8, near Genoa, has also been outfitted with underwater speakers that produce low-frequency noise known to deter carp but not other fish, Sorensen said.
Nanette Bischoff, an Army Corps project manager in the St. Paul District, said the agency is collaborating on similar water flow adjustments at Lock and Dam 5 south of Lake Pepin. Sorensen has a proposal to install underwater speakers at that lock, too.