Researchers Deploy a Shocking Method of Fish Collection

A group of fisheries scientists from Tennessee Tech University are busy monitoring the health of the Caney Fork River by pumping electricity into the water.

Though water and electricity are not usually a good mix, the combination is one of the best methods for collecting fish and determining their health. The electricity stuns them long enough to allow them to be scooped up in long nets, measured and tossed back.

“The integrity of the Center Hill Dam has been compromised and as the engineers fix it, everything downstream is changing and people want to know about it,” said Phil Bettoli, the primary investigator of the project and assistant leader of the U.S. Geological Survey’s Cooperative Fishery Research Unit, a joint effort between TTU, USGS, the U.S. Fish and Wildlife Service and the Tennessee Wildlife Resources Agency.

“The Army Corps of Engineers hired us to do the assessment of what is going on in that fish community now, but when they finish their repairs to the dam, they may go back to the way they used to operate the dam which is going to change the fish community again. We want to be able to predict what’s going to happen then.”

As engineers pump concrete into areas where the water has eroded the limestone into which the dam was built, a team of TTU researchers is collecting fish on the river at five locations below the dam. They have been there for two years and will be there for the next year and a half, working with two grants worth nearly $300,000 from the Army Corps of Engineers.

In the nearly four years that the dam repair has been underway, the biologists have found that the ecosystem has gotten healthier. The engineers have used a small gate that releases water and also aerates it at the same time, providing more dissolved oxygen for the fish and insects in the river. Also, water is being released on a more regular basis to lessen pressure on the structure, which provides a more consistent environment for the organisms living downstream.

“The dam was built for two main reasons; for electricity and flood control,” Bettoli, who is also a professor of biology at TTU, said. “They didn’t think about wildlife habitats in the 1940s when they built this. Now, you can’t ignore it.”

Researchers from a team of more than a dozen undergraduate and graduate students can be found on the river during all four seasons, at all times of the day. They are found either in a small flat-bottomed boat equipped with a small generator and long probes that run an electric current through the water, or wading through the river themselves with packs that generate electricity on their backs, nets in hand.

“I wanted this job because a lot of rivers are having the same issues the Caney Fork is,” said Tomas Ivasauskas, a TTU graduate who is working on the project. “If the engineers weren’t pumping the concrete in, the whole dam would have been compromised.”

Once the study is complete, their work will also provide a baseline of information for dam operators, as well as the TWRA, which manages a popular trout fishery on the river and the U.S. Fish and Wildlife Service, which is interested in the impact of the work on the Cumberland River and its endangered mussel populations. With the knowledge, they will be able to monitor the effects of the dam on the river and change their operations, if necessary.

Nearing the end of the first two-year grant, the team is getting ready to present its research. Studying fish populations below dams is difficult because researchers must alter their schedules to work around the various times the dam is generating power. Biologists also tend to consider dammed rivers to be artificial ecosystems; many native species are often killed off when a dam is built and other, nonnative species move in.

“There’s not a whole lot of this kind of work going on in North America under large hydroelectric dams,” Bettoli said. “The thinking was that people were not interested in the biotic integrity of radically altered systems. We expect a lot of questions and interest from our peers.