Putting mussels on the path to recovery in North Carolina

On the banks of western North Carolina's Tuckasegee River, T.R. Russ, a biologist with the North Carolina Wildlife Resources Commission, gently pries open the shell of an Appalachian elktoe mussel (Alasmidonta raveneliana)—just enough to see if it is a female laden with young.

A handful of adult elktoes carrying young are destined for a state fish hatchery in Marion, where they will become part of an effort to raise some of the state's rarest mussels in captivity with the expectation that stocking will be a powerful tool in boosting wild populations and improving the status of these species.

At least 58 species of native freshwater mussels are known from North Carolina waters, though at least seven have vanished from the state. Habitat loss and degradation are the primary factors contributing to the dramatic decline in native freshwater mussels. Of the surviving species, 43 are recognized by the as endangered, threatened, or of special concern by the state, and seven are listed as federally endangered or threatened under the Endangered Species Act.

"Declining mussel populations are a red flag for humans," said Sarah McRae, a biologist in the U.S. Fish and Wildlife Service's Raleigh Ecological Services Field Office. "Mussels are very sensitive to changes in water quality and if their numbers start to drop, it tells us there's a problem with the stream. Caring about the well-being of our creeks and rivers means caring about the well-being of our mussels—they're inseparable."

The Appalachian elktoe – native only to the mountain streams in western North Carolina and eastern Tennessee – is both state and federally endangered. Adult elktoes taken from the Tuckasegee River – one of the best remaining populations – will be held at Marion hatchery for propagation. The reproductive cycle of the Appalachian elktoe is similar to that of other native freshwater mussles. Adult elktoes will release their glochidia, or larvae, into the water, which parasitize for a short time on a host fish while they develop into juvenile mussels. Juvenile mussels will detach from their host fish and drop to the bottom of their tanks, where they will continue to grow. Once large enough, the elktoes will be released into the wild to help bolster populations in areas where the habitat has improved in recent years—like the remote Cheoah River in southwestern North Carolina.

"With the Cheoah, we really have an opportunity to take a big step forward in conserving the Appalachian elktoe," said John Fridell, a biologist in the U.S. Fish and Wildlife Service's Ashville Ecological Services Field Office. "Beyond that, success with the mussel rearing efforts at the Marion hatchery should really help us improve the status of small populations hanging on in other rivers across western North Carolina, and eventually reintroduce the species into some of the streams from which it has been eliminated."

Another rare mussel reared at Marion is the Tar River spinymussel (Elliptio steinstansana), which is found only in eastern North Carolina, in the Tar-Pamlico and Neuse River basins. The species – one of only three U.S. mussel species with spines – gained federal protection in 1985, after its populations declined to precariously low numbers.

In 2007, a team of federal, state, and private biologists identified a need for rescuing, holding, and propagating the species to maintain genetic diversity, provide offspring for stocking, and investigate the animal's life history and habitat requirements. The group identified Fishing Creek and a headwater tributary, Little Fishing Creek, which runs through Medoc Mountain State Park, as the top priority stream for stocking and other conservation efforts for the Tar River spinymussel.

Young Tar River spinymussels are kept at Marion until they are ready to reproduce. When ready to spawn, the mussels are transferred to a laboratory at North Carolina State University in Raleigh for hands-on care. Once offspring have matured, they are transported back to Marion, where they continue to grow and start the cycle again.

Driving these captive propagation and rearing efforts is a partnership between the Service, the Commission, and the university. Through this collaborative effort, biologists bring together knowledge about the plight of wild mussel populations, aquaculture, and other areas to restore these rare mussels in North Carolina rivers.