Asian carp increasing in Mammoth Cave

In Mammoth Cave National Park, visitors and staff are spotting an invasive species in Nolin River and Green River – the Asian carp.

“We’re seeing them more frequently, more now than in 2017,” said Rick Toomey, cave resource management specialist and research coordinator for Mammoth Cave National Park. “They’re becoming more common. They are becoming more numerous. They’re continuing to expand their range.”

Asian carp – an umbrella term for bighead, silver, black and grass carp – eat plankton, which native mussels and fish rely on, according to Eric Cummins, the Warren County fisheries biologist for the Kentucky Department of Fish and Wildlife Resources.

“They filter out that base source of the food chain that every fish has to eat at some point in their life cycle,” Cummins said. “They may be competing with small fish, and that kind of snowballs itself as you go up the food chain.”

That damages the ecosystem and threatens vulnerable populations, including the region’s federally endangered freshwater mussel species native to Kentucky waters.

The fish can also directly pose threats to humans. Asian carp jump out of the water, and sometimes land on boats or knock people down.

“They’re very sensitive to disturbances,” Cummins said. “They can jump in the boat with you.”

At Mammoth Cave, this isn’t as rare as it might sound. In the past few years, “we’ve had several situations where they’ve actually jumped into boats that were being run by park staff,” Toomey said.

There has been particular concern in the Green River, which is considered the fourth-most biologically diverse river system in the U.S.

In 2017, the U.S. Fish and Wildlife Service, along with partners such as the Kentucky Waterways Alliance and Mammoth Cave, removed Lock and Dam No. 6 from the Green River.

There are plans to remove Lock and Dam No. 5, which is about 14 miles downstream from Lock and Dam No. 6. The dam could be creating a barrier and preventing the Asian carp from swimming upstream, but its removal would ultimately be environmentally beneficial – even with the potential consequence, according to Ward Wilson, executive director for the Kentucky Waterways Alliance.

However, the river levels get higher than the dam during heavy rains, so it might not even be a significant barrier.

“The dams may be reducing how many are effectively invading,” Toomey said, but “when water is simply flowing over the dams, the fish would be able to get over them.”

Park staff are trying to keep tabs on the Asian carp population, but it’s mostly observation at this point, according to Toomey.

Toomey believes the situation will require collaboration between various organizations and coordinated efforts along each waterway.

In March, President Donald Trump signed into law the Natural Resources Act, which includes legislation that requires agencies to develop methods of reducing and eliminating invasive species populations – including Asian carp.

But currently, there hasn’t been enough work to protect Kentucky waters, according to Wilson.

“Most of the work going on with Asian carp is preventing them from getting into the Great Lakes,” Wilson said, “but there are some people controlling them in the Kentucky rivers.”

The Kentucky Waterways Alliance recently signed a letter to Congress requesting more funding to handle the issue.

Both Cummins and Toomey suggested that the regional situation wasn’t quite the crisis level of other areas.

“We’re not seeing them at the level that the state is reporting them at Lake Barkley or in the Ohio River,” Toomey said, but “by the same token, they’re in the river.

“We remained concerned about Asian carp.”

By Caroline Eggers
Bowling Green Daily News