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Controlling invasive carp with sound waves

A team of researchers from Virginia Tech has recently received a $340,000 grant from the U.S. Army Engineer Research and Development Center (ERDC) to create new tools using sound waves to control the movements of invasive species of Asian carp. The ERDC is an organization which aims, among other things, to manage United States’ commercial waterway infrastructure, including locks and dams.

Asian carps were introduced into targeted waterways in the 1970s to control harmful agents on aquatic farms. However, over the past half a century, these invasive fish have moved beyond aquatic farms and currently threaten the balance of aquatic life in many lakes and rivers across the U.S, gobbling up food and resources needed by other animals, and thus threatening the fishing industry too. Moreover, one type of carp can leap out of the water at a distance of several feet, often endangering boaters.

According to the scientists, the continuous spread of the species is mostly related to human activities. For instance, transported young carp may accidentally be dumped into water from travelling boats, and then mature and breed in areas where they do not belong. In addition, carps take advantage of the movement of boats and water where lakes and rivers meet – intersections that are usually controlled by dams and locks. 

In the case of locks, engineers construct small waterways between two larger waterways. When a boat enters, both sides of the lock are closed, and, when one waterway is higher than the other, the lock will either be flooded so the boat can travel “uphill,” or drained so the boat can move “downhill.” During that water movement, nearby carps can enter the lock and create a new habitat in the waterway. Thus, since the carp move most easily through the lock transition, the idea behind Virginia Tech’s new project is to keep them away from those areas.

While many previous technologies – such as combinations of nonlethal barriers at locks and dams to deter the fish, including electrical barriers or columns of bubbles – already exist, they are not focused specifically on carps, but affect instead a large variety of fish species. Now, the research team led by John Palmore (an expert in Computational Fluid Dynamics at Virginia Tech) aims to use sound to deter carp.

“Out of all those technologies, acoustic deterrents are potentially the best in the sense that they are the most customizable,” Palmore explained. “All fish are affected by bubble currents. Electric fences contain fish based on size but not species. For acoustic deterrents, each species hears within a different range. You have a selective mechanism to annoy specific species of fish.” 

To keep carp at bay with sound, the researchers will combine different noises, such as predatorial sounds, boat noises, and other irritants. “The goal is to generate a model that can be applied widely to rivers and dams. Information such as the shape of the riverbed and the lock, how often barges enter, and how long it takes to fill the lock are important to our study,” Palmore concluded.

By Andrei Ionescu, Staff Writer

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