Round Hickorynut Mussel

This photo shows an example of the Round Hickorynut Mussel found by biologists last week when rescuing mussels that had been exposed due to decreasing water levels in the Green River. 

MAMMOTH CAVE NATIONAL PARK — When a team of biologists visited Mammoth Cave National Park last week to rescue mussels that were in danger of losing their habitat due to decreasing water levels in the Green River, they found a species of mussel that has not been seen in the river for many years.

The mussel species they found was the Round Hickorynut.

“We just happened to run across them,” said Monte McGregor, an aquatic biologist for the Kentucky Department of Fish and Wildlife Resources, who is also the director of the department's Center for Mollusk Conservation, adding that it is has probably been 15 years since that particular species of mussel has been found in the Green River.

Two things have caused the water level of the river to decrease and the mussel beds to be exposed — a drought followed by the breach of lock and dam No. 6 near Brownsville in Edmonson County.

Mussels need to be underwater in order to survive. The biologists relocated the mussels that had been exposed due to low water levels to an area of the river where the water levels are not likely to fall. In doing so, they found about four of five of the Round Hickorynut mussel, one of which was female.

The Round Hickorynut mussel is found in other rivers across the state, including the Licking River, upper Kentucky River, Buck Creek and a few tributaries of the Ohio River in eastern Kentucky, but very few have been found over the years, McGregor said.

“It's not to the point that it is on the federal endangered species list,” he said, but the species is listed on the state's Species of Greatest Conservation Need along with 45 other mussel species.

McGregor took the Round Hickorynut mussels back to the Center of Mollusk Conservation so he can grow the species and try to keep it from becoming endangered.

Also during the mussel relocation on the Green River, the biologists found two species of mussel, the Fanshell and the Sheepnose, that are on the federal endangered species list.

They are two out of 27 mussel species that appear on the state's Species of Greatest Conservation Need list and are also on the federal endangered species list.

It is possible that the biologists will have to return to the Green River to do more mussel relocations.

“As soon as we see the conditions get as low as it can get, we will have to go back again,” McGregor said. “I don't think that will happen again until next summer.”

Since the breach of lock and dam No. 6, national park officials have been checking the river level daily.

“We are watching it very carefully,” said Vickie Carson, public information officer for the national park.

There are two automated gauges that record the water level in the river at Munfordville and at Brownsville. The readings recorded by those gauges can be viewed online at https://waterdata.usgs.gov/ky.

“We look at those every day and of course we have the ferrymen down at the ferry as well at the river there,” Carson said.

So far, since the breach of the dam the national park has had to close access to the Houchin Ferry area of the Green River, but the river level has not decreased so much that the Green River Ferry in the national park has not been able to operate.

The Green River Ferry, however, is not currently running due to a mechanical failure and will be out of service for about 10 to 14 days, she said.

National park officials are not sure how low the river level will have to fall to keep the ferry from being used. They have sought a permit from the U.S. Army Corps of Engineers to do some modifications at the ferry, if needed, that call for the addition of rock and some dredging that will help keep the ferry operating, said Bob Carson, chief of the national park's science and resource management division.

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