Could electric ‘fish fence’ block carp invasion in Salt River basin? KY wants to know.

A federally-funded study approved Friday by a board overseeing Kentucky’s wildlife management department will look at potential locations to develop an electric “fish fence” to block invasive carp on the Salt River — and harvest them straight out of the water onto a conveyor belt. 

Dave Dreves, the director of fisheries for the Kentucky Department of Fish and Wildlife Resources (KDFWR), told the Kentucky Fish and Wildlife Commission that the $40,000 feasibility study would look to see if an electric “fish fence” system developed by a University of Minnesota professor to harvest carp could be installed on the Salt River basin.

For more than a decade, invasive carp species — which include bighead carp, black carp, grass carp and silver carp that are known to jump into the air — have been an ecological problem in some Kentucky waterways because of their ability to outcompete native fish for food, reproduce  and grow larger than potential predators. Invasive carp have traveled along the Ohio River into Kentucky tributaries where fishermen have been given subsidies to fish out millions of pounds of invasive carp every year, including in Kentucky Lake and Lake Barkley in Western Kentucky. 

Another way to curb the invasive fish is through blocking their passage. That method — a “fish fence” — is being tested by KDFWR,  working with federal and private partners, at Lake Barkley. It uses a combination of light, sound and bubbles to deter the invasive carp from entering the lake. 

The new study approved by the KDFWR board would instead look at the potential of using electricity through a system developed in Minnesota to block and harvest invasive fish entering the Salt River basin. The developer of this electrical “fish fence” told the Lantern he created the system to automate the removal of invasive carp. 

“I don’t know of too many practical, useful automated technologies in fish management, and I think this is one of the first ones, you know, what we developed,” said Przemek Bajer, the owner of the invasive fish management company Carp Solutions and a research assistant professor at the Minnesota Aquatic Invasive Species Research Center. 

Bajer has developed a system on Minnesota waterways to corral common carp, another invasive species, into a trap using a wall of electrodes placed in the water that fish can’t swim through. Electrical pulses from the electrodes then push the common carp into a trap adjacent to the electric wall, where more electrodes are activated in sequence to force the carp onto a conveyor belt out of the water where they can be harvested by hand. Bajer believes such a system could work in Kentucky, though the feasibility study approved by the department would help determine that.

“You don’t have to be like, you know, in the water or on the water, manually, laboriously removing the fish. You have a technology that does most of the work for you,” Bajer told the Lantern. 

The KDFWR considers the lower basin of the Salt River watershed, which connects to the Ohio River in Hardin County,  to be an “establishment front” for invasive carp. That means invasive carp of all ages are present and reproducing which warrants “special attention” from wildlife management officials to monitor their spread. 

The department announced earlier this week that surveillance DNA testing of Taylorsville Lake, an important fisheries resource in the Salt River basin, found positive test results for invasive carp DNA in the lake but no confirmed presence of silver carp or bighead carp. 

In two studies provided by Bajer to the Lantern, roughly 90% or more of common carp tracked by researchers in Minnesota were blocked by the electrical field created from the electrodes. In one of the studies, a little over half of all tracked carp in the first year of the study were harvested, and the second year of the study saw a little over two-thirds of tracked carp removed. Bajer also pointed to efforts in other states to use similar systems to block the advance of sea lampreys. 

Bajer said a downside of the system is that the electric wall will stop all fish species, native and invasive, within a certain size range. But he said native fish species can be filtered out in the conveyor system by hand if caught in the trap, and the system is portable and efficient at blocking the invasive carp. Another downside is that the system places a lot of metal in the water, making it not very compatible with waterways that have a lot of boat traffic. 

The implementation of such a system in the Salt River isn’t guaranteed and wouldn’t happen anytime soon. Bajer said the feasibility study would determine if there are suitable sites along the river to implement the system. If there are sites, he said, he believes lab tests would likely be done to determine how bighead and silver carp react to the system. If those lab results are favorable, then testing would move into the field. 

The KDFWR anticipates a final report for the feasibility study would be completed by October 2025.

“It can be very effective,” Bajer said. “The fish are running out of the stream on a conveyor belt.”