Raleigh, North Carolina – Biologists working in the Little Tennessee River, home to what until recently was the healthiest population of the endangered Appalachian elktoe mussel, are noting a seemingly inexplicable and dramatic decline in the population.

Biologists with the N.C. Wildlife Resources Commission have been surveying mussels in the Little Tennessee River between the town of Franklin and Fontana Reservoir for the past two years as part of a mussel reproduction study. During that time, they’ve noted a long-term decline in the number of Appalachian elktoe mussels and an acute die-off.

“It’s baffling,” said Steve Fraley, an aquatic biologist with the Commission. “In a relatively short time, they’ve gone from being fairly abundant to relatively rare at the majority of our monitoring sites.”

For every hour biologists spent looking for the mussels in 2004, they found 6.1 elktoes. In 2006, that number was down to 0.8. Some of the decline may be explained by mortality directly connected with the flooding from tropical storms Frances and Ivan; but since then, biologists have noted a continued decline. To confound the issue further, populations of five other mussel species surveyed in the same area at the same time appear stable over the same period, despite the tropical storms.

There is no obvious reason for the decline, though at this point biologists aren’t ruling out anything — disease, parasites, toxins or stressors could have weakened mussels to the point that they succumbed to something that typically isn’t a problem.

“It really is a sad situation,” said John Fridell, the U.S. Fish & Wildlife Service biologist who listed the mussel as endangered in 1994. “The Appalachian elktoe had been making strides across the region, then Frances and Ivan struck, which negated some of those gains. Now we see this degree of a decline in what only a few years ago was the healthiest, most numerous population.”

This past winter, biologists noted an acute die-off of mussels. This prompted them to send tissue samples to the U.S. Geological Survey and Virginia Polytechnic Institute looking for pathogens and parasites, but results were inconclusive. As mussel populations have continued to decline over the past few months, biologists may conduct further pathological and toxicological analyses.

The Appalachian elktoe (Alasmidonta raveneliana) was federally listed as endangered in 1994. Today, there are seven known populations: in the Upper Nolichucky River basin of Mitchell and Yancey counties, the Mills River in Henderson County, the Little River in Transylvania County, the West Fork Pigeon and Pigeon rivers in Haywood County, the Tuckasegee River in Jackson and Swain counties, the Cheoah River in Graham County and the Little Tennessee River in Macon County.

If resources are available, biologists hope to conduct a detailed review of existing water quality data and increase water quality monitoring on the Little Tennessee River, looking for any anomalies or trends that may be linked to the decline.

The Little Tennessee River begins in North Georgia, flows north and then west across North Carolina, before flowing into the Tennessee River. In 2004, it was the site of a conservation milestone as numerous partners came together to purchase 4,500 acres straddling the river below the town of Franklin, the so-called “Needmore Tract.” This move was seen as a huge step toward protecting the quality of the Little Tennessee River, which in turn, helps ensure the success of the Appalachian elktoe mussel.