Broadcasting underwater noise may be a sound solution for repelling Asian carp on Mississippi River

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A silver carp is tagged with an acoustic transmitter (black tag located on the fish’s back) to monitor movement in the Mississippi River. Fish were monitored in response to the recording of a boat motor as part of the “Use of Sound to Alter Behavior of Silver Carp and Bighead Carp” research conducted by the United States Geological Survey.

Field implementation of sound as a deterrent to movement of bighead carp through a constructed lock approach channel was conducted by the United States Geological Survey. Six speakers were suspended off rafts across the middle of the channel, and a recording of a boat motor was played in both directions (to the left and right in the photograph) to deter fish passage through the channel. (Photos submitted)

By Ted Pennekamp

How can Asian carp be stopped? That is the question that biologists and other researchers have been working on for many years in their continuing quest to deter the invasive species from advancing up the Upper Mississippi and many other rivers.

A new effort at Lock and Dam 8 near at Genoa hopefully offers a sound solution to the problem, which, if it works well, will be implemented at other area locks and dams, possibly including Lock and Dam 9 near Lynxville.
The U.S. Army Corps of Engineers, St. Paul District, recently changed the way it operates the spillway gates on Lock and Dam 8 in response to recommendations from a University of Minnesota research team led by Dr. Peter Sorensen. The proposed alterations are the result of several years of study of Asian carp movement and deterrent techniques funded by the Minnesota Environment and Natural Resources Trust Fund. These changes were carefully designed to stop carp passage while having minimal effects on native fish, fishing and lock and dam infrastructure.

Research had shown that there were small flow imbalances that might have been allowing adult Asian carp to swim through the dam. Making relatively small adjustments to gate operations will prevent this without affecting barge traffic and these adjustments cost nothing.

The most intriguing aspect of trying to repel Asian carp at the dam, however, was the installation of underwater speakers in the lock gates to broadcast low-frequency noises that deter carp but are not known to affect important native species and also are not audible to people on the river.

“Quite a bit of work has gone into the use of sound to repel/direct fish. The US Geological Survey, US Fish and Wildlife Service and the University of Minnesota have explored the use of sound,” said Robert Wakeman, the Statewide Aquatic Invasive Species Coordinator, Lakes and Rivers Section, Bureau of Water Quality, Wisconsin DNR. “We know that the sound of an outboard motor causes silver carp to jump out of the water.

Further research has confirmed that ‘complex noise’ may deter the movement of Asian carp, so work is being conducted at locks and dams 2 and 8 to see if complex noise at a lock and dam structure on the Mississippi River would stop the upstream movement of Asian carp.”

Depending upon the success of this technology, Wakeman said additional locks may be outfitted with speakers and used to deter Asian carp movement. He said sound barriers are also being proposed on the Des Plaines River as part of the Brandon Road Asian carp barrier.

“The Asian carp population in the Mississippi River along Wisconsin is believed to be relatively low. Asian carp are sporadically captured by anglers/commercial harvesters but not in very high numbers,” said Wakeman. “There are differences in opinion on the level of threat the Asian carp may represent to the upper river.  Some don’t think they will find enough food to do well, while others speculate that it is just a matter of time before their population increases. One of the most important things we can do to help fight Asian carp in the upper river is to keep the habitat as healthy as possible for our game fish.”

According to the Minnesota Department of Natural Resources, bighead and silver carp are now abundant and reproducing in Iowa, about 100 miles south of Genoa, and continuing to move north. These fish are known for their voracious food habits and tendency to jump, startling boaters on the Mississippi.

The jumping of the silver carp (also known as head butting carp) can potentially injure boaters, but that is not the main concern regarding their movement up the Mississippi River. The main concern about silver carp and bighead carp (which are two separate species of Asian carp), is that they reproduce and grow very rapidly once established in an area and they also are huge eaters of plankton and plants which other species, such as small forage fish and sport fish, need.

“These Asian carp species are a serious concern because they can aggressively compete with native commercial and sport fish for food and can potentially disrupt entire ecosystems,” said a recent report by the University of Minnesota and the US Army Corps of Engineers.

“Asian carp have few natural predators because they quickly outgrow native predator species, often within just a year. In parts of the Illinois River, silver carp and bighead carp make up more than 90 percent of the fish biomass, essentially out competing all native species for food and habitat,” according to a comprehensive report on Asian carp released on Oct. 30 by the Great Lakes Sea Grant Network.

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