A team of University of Minnesota scientists thinks it has figured out how to keep invasive carp from migrating up the Mississippi River: Blow them back with jets of water and freak them out with loud noises, air bubbles and underwater lights.
With preliminary blessings from state and federal agencies, they’re looking for money to put their idea into action.
“Do we just wait for the Asian carp to invade?” asked Prof. Peter Sorensen, who heads the team. “That’s kind of what’s happening now.”
Sorensen said his group has initial support from the Army Corps of Engineers and the Minnesota Department of Natural Resources for the construction of a barrier at the Army Corps’ Lock and Dam No. 5, upstream from Winona.
After three years of research, the team believes the 81-year-old structure is uniquely suited for blocking bighead carp and silver carp from migrating to the upper Mississippi, St. Croix River, Minnesota River and connected lakes.
Sorensen will propose full-scale implementation in March meetings with the DNR, Lessard-Sams Outdoor Heritage Council and the Legislative-Citizen Commission on Minnesota Resources. Federal funding also may be required for the solution, which Sorensen estimates will cost $7 million to $10 million. It’s too early to say who would own and operate it.
“We’ve got the tools necessary to do this and there’s no point in waiting,” said Sorensen, a fish scientist noted for his work to control invasive sea lamprey in the Great Lakes.
The multidisciplinary approach by Sorensen’s team would manipulate the lock and dam’s spillway gates to create consistent, high-velocity stream flows too powerful for the carp to overcome. Crews also would install a noise-blasting system paired with lights and a sophisticated, deflecting shield of air bubbles.
Thirdly, Sorensen said his team has refined DNA testing of water samples to quickly detect the presence of bighead and silver carp. When the invaders aren’t in the pool that sits below the lock and dam, the barrier system could potentially be disarmed to allow for the migration of game fish, he said.
Nanette Bischoff, project manager for the St. Paul District Corps of Engineers, said the agency has been cooperating with Sorensen’s team for several years and sees no negative consequences for navigation.
In fact, the team’s computer simulations of revised spillway gate settings at Lock and Dam No. 8, near Genoa, Wis., show how the redistribution of stream flow could more evenly block Asian carp without increasing scouring of the river bottom — an important consideration for the Corps.
Bischoff said a civil engineer on Sorensen’s team, Dan Zielinski, “definitely has the latest and greatest model” to redistribute water through gated spillways. “It’s a question of how can we modify balance of flow to make it more difficult for carp,” she said.
Bischoff said the university’s researchers have worked with the Army Corps of Engineers research station in Vicksburg, Miss., to define the swimming characteristics of Asian carp. Using a swim tunnel, the scientists witnessed what stream velocities were too great for the fish to overcome.
Zielinski said the study showed the carp are “ordinary” swimmers, far less than the salmon-like performance that was expected. He incorporated the information into his computer modeling of water velocities that would be too powerful for the fish to get through.
While many lock and dam spillway velocities are jet-like and impassable, Zielinski discovered in the pilot project at Lock and Dam No. 8 that the velocity in other spillway gates fluctuates enough for a small percentage of the largest silver and bighead carp to migrate upstream in early spring, when gates are lifted high and velocity drops. The low passage rates explain why there have been only isolated findings of the fish in the St. Croix and the recent catch of a 25-pound bighead carp in the Minnesota River near New Ulm.
“Lock and Dam No. 5 is less passable and more promising than No. 8,” Sorensen said.
The DNR provided $800,000 to Sorensen’s pilot project at Lock and Dam No. 8 and has been meeting with him to understand the details of his current proposal, said Nick Frohnauer, the agency’s invasive fish coordinator.
“It’s something worth exploring,” Frohnauer said Friday.
The great fear of Sorensen’s team, fisheries biologists and anglers is that the aggressive carp eventually will migrate in numbers large enough for them to become established in Minnesota, where they would cut deeply into food sources now available to other aquatic species. So far, the DNR has said, there’s no proof the carp are reproducing in Minnesota.
Sorensen said there’s no guarantee some Asian carp won’t get around the proposed barrier 10 miles north of Winona, but the already-infrequent incursions by the fish would become exceedingly rare.
Sorensen’s desire to use underwater noise as a deterrent to carp migration is well known and his team has been testing the technology. As refined by university researcher Clark Dennis III, the proposed noise, light and bubble barrier would blast sound akin to boat motors into the water. Dennis said Asian carp have keen hearing systems and most definitely keep away from boats.
Sorensen said a British company that works with acoustic technologies to keep fish away from power plants has visited Minnesota and signaled the noise barrier is “very doable.”
If Minnesota does nothing to stop the upstream migration of bighead and silver carp, Sorensen said, enough of the fish will sooner or later find their way north of Lock and Dam No. 5 to populate above the dam, where there’s no better infrastructure to stop them.
In Keokuk, Iowa, less than 300 miles south of Winona, Asian carp swarm the river just below Lock and Dam No. 19. Jessica Eichmiller, a researcher on Sorensen’s team who has been refining the use of DNA water sampling to detect the fish, said Asian carp in that area easily exceed 50 percent of the river’s biomass. In Keokuk and other places, she said, there’s no solution for getting rid of them. “The only solution is prevention,” she said.