BENSON — Absent the political will in Congress to close the Mississippi River lock system at St. Paul, the only certain means of stopping Asian carp from making their way upstream is off the table.
The Minnesota Department of Natural Resources has turned instead to the possibility of spending $12 million to build a light, noise and bubble fish barrier at the Ford dam.
Some legislators would prefer an electronic barrier, which the DNR backed away from as too dangerous and not likely to receive approval from the U.S. Corps of Engineers.
No matter the choice, to know how challenging it will be to develop any sort of effective barrier requires no more than a trip to Hassel Lake north of Benson.
In 1992, an electronic fish gate was installed on the small stream that connects Hassel Lake with the Chippewa River. The lake was treated to kill the common carp that fill its waters, and the electronic barrier was energized.
Two decades later, carp remain the lake’s biggest problem.
Dave Soehren, now retired, was an area wildlife manager with the DNR and the first to confront the challenges of making a fish barrier work. Flood waters in 1997 and 2001 circumvented the barrier. And one year, an electric malfunction de-energized the barrier long enough for the carp to return to the lake, he said.
Curt Vacek is the DNR’s wildlife manager working on the project today. He said the barrier is effective at keeping carp from the lake, when it operates. The electrodes corrode in the water and have limited life spans.
The barrier is working right now, but there are carp on both sides of it, in the lake and the stream.
Common carp root out the native aquatic vegetation that otherwise make Hassel Lake a top-notch feeding and resting draw for migrating waterfowl. Vacek said the DNR is looking at different options, and will be deciding soon on a new strategy to restore this lake for waterfowl.
The likely choice will be a system that relies both on the fish barrier and the ability to draw down the lake and kill carp when they do re-infest the lake. The past two decades have shown that there is no such thing as a fail-safe fish barrier.
Speaking earlier this year at a roundtable hosted by the DNR, Peter Sorensen, director of the University of Minnesota Aquatic Invasive Species Research Center, was quick to warn that any sort of barrier would at best only delay the upstream migration of Asian carp.
After his own experience on the small stream connecting Hassel Lake, Soehren is among those who know just how difficult it would be to develop an effective barrier on a waterway as large as the Mississippi River or for that matter, the Minnesota River.