Since the 1970s invasive Asian carp have steadily migrated north into the U.S. Midwest, infesting the watersheds of the Mississippi, Missouri and Illinois rivers. The voracious bottom-feeders can strip entire river ecosystems of zooplankton, the basic food of native fish species—and now they seem poised to breach the Great Lakes ecosystem. Earlier this summer a commercial fisherman contracted by the Asian Carp Regional Coordinating Committee (ACRCC) caught a species of the intruding fish in Illinois, only 14 kilometers south of Lake Michigan.

That sobering find in the Des Plaines River has engineers and scientists scrambling for a way to halt these slippery aliens. An adult Asian carp can weigh 45 kilograms and eat the equivalent of 5 to 20 percent of its body weight every day. Scientists estimate an established breeding population of Asian carp could devastate Lake Michigan’s $7-billion commercial and sport fishery by devouring the food sources native fish need to survive. “Asian carp, in particular bighead and silver carp [such as the one caught in June], feed on the small food items at the very base of the food chain. They do that very efficiently,” says John Dettmers, director of fisheries management at the Great Lakes Fishery Commission. “Other invasive species like zebra and quagga mussels have [already] dramatically shifted the structure and energy flow of many of the Great Lakes ecosystems.” Fish farmers imported Asian carp to the U.S. from China decades ago in an attempt to control phytoplankton blooms in aquaculture ponds and sewage treatment lagoons in Arkansas. The fish escaped into the Mississippi River watershed when floods breached the man-made lagoons.

Last month the U.S. Army Corps of Engineers released an extensive report proposing technology-based solutions that could be installed at the Brandon Road Lock and Dam on the Des Plaines River in Joliet, Ill.—one of the last physical barriers between the Mississippi River and Lake Michigan. Army Corps researchers looked at 98 different technologies before choosing an electric barrier paired with “complex noise” generation. Electricity and complex noises—imagine hearing white noise continuously while underwater—play havoc with the Asian carp’s sensory mechanisms.

The electric barriers send low-voltage, pulsing direct current (DC) through underwater electrodes. This creates an electrified field from the bottom of the channel to the top of the water column. As an adult fish nears the barrier, its body tingles in response to the electric current. If it moves closer, the result is a more painful shock. The electric current also disrupts the fish’s ability to maintain its position in the water current. “Fish that encounter electricity go through a process called galvanotaxis that immobilizes the muscles, physically stopping the fish from moving through the barrier. The process can be lethal,” says Mark Cornish, a supervisory Corps biologist. A series of powerful water jets sweeps the stunned or dead fish away from the barrier.

In addition to the electrical barriers, the Corps would attach speakers to the walls and bottom of an engineered concrete channel, and these would emit sounds to chase away the fish. Sound was initially dismissed as a possible deterrent when research revealed fishes become acclimated to constant tones and would eventually move through a sonic barrier. Scientists studying Asian carp in the Mississippi and Missouri rivers have noted, however, that this species will consistently leap out of the water when exposed to the complicated sounds of a motorboat engine. “The sensory mechanisms inside the fish are aggravated and will avoid complex noises,” Cornish says. “We’re developing models to maximize the output of that complex noise so that we can create the perfect acoustic environment for deterring fish.” These new devices would be used in addition to commercial fishing efforts at the Brandon Road site that remove over one million pounds of bighead and silver carp annually.

“This may be the first facility in the world to use behavioral deterrents to control invasive species in large rivers,” says Peter Sorensen, a professor in the University of Minnesota’s Department of Fisheries, Wildlife and Conservation Biology. He works at the university’s Minnesota Aquatic Invasive Species Research Center and specializes in Asian carp, focusing on detection, control and management in the Mississippi River watershed. “The proposed use of sound is novel, interesting and very promising,” he says. But in order to be successful, the engineers and researchers will first have to figure out the optimal sound. “Both the manner with which sound travels through shallow water and the way that individual species of fish perceive it are complex and not intuitive,” he says. “Physics, engineering, sensory physiology, behavior and the environment all factor in,” he adds. “These are intelligent fish that learn and remember. Developing and implementing deterrents that function well in the aquatic world of the carp is a fascinating challenge. One has to think like a carp.”

Before the Corps can install any of these deterrents at the lock and dam complex, its recommendations must navigate a series of public hearings and Congressional budget approval as well as a still to-be-determined construction time line. Federal agencies, nonprofit organizations, state government officials and commercial interests all play a role in the decision-making process. Most of the parties involved say that process has been collaborative—but disagreements about the impact on the Asian carp, cost-sharing and questions about the effectiveness of proposed technologies have caused delays and call into question just how well the various groups are working together.

Meleah Geertsma, a senior attorney for the Natural Resources Defense Council Midwest Program, paints a less-than-harmonious picture of the effort. “We’ve seen an overall reluctance for the federal agencies to take a position on a solution, given the amount of pushback from entities like the State of Illinois and the waterways operators,” she says. “Unfortunately, consensus has been elusive. A process that in theory could move faster, if there was the will and an agreed-upon solution, is really getting bogged down.”

Those in charge of protecting the Great Lakes from such an ecological menace are hoping the differences will be resolved soon. As Dettmers puts it, “In the realm of invasive species, we know that prevention is so much more effective than trying to control something after a population has been established and starts to spread.”