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The Nolichucky River is turbid, its water resembling a color close to chocolate milk. It has been over eight months since Hurricane Helene swept through western North Carolina and eastern Tennessee, bringing with it historic levels of flooding in several watersheds, including the Nolichucky. Prior to Hurricane Helene, the Nolichucky River was home to a species rich assemblage of freshwater mussels. Now, staff from Erwin National Fish Hatchery, the Tennessee Ecological Services Field Office, and the Asheville Ecological Services Field Office are working to discover the impacts of Hurricane Helene on the freshwater mussels in the Nolichucky River.
Surveying for freshwater mussels is a slow, careful process, even in the best of conditions. Mussels often hide in the substrate, with only the tips of their siphons visible. Biologists will snorkel through the river, carefully looking for the mussels. It can be difficult to spot the mussels, especially when conditions are poor. High turbidity and increased flow from rain can make it even harder to spot the mussels, reducing visibility and making it more likely that the mussels will remain shut tight, decreasing the likelihood of spotting the siphons.
The Nolichucky River contains multiple reintroduction sites, where the Tennessee Wildlife Resources Agency (TWRA) stocked multiple species of imperiled freshwater mussels that historically occurred in the Nolichucky River. Assessing the impacts of Hurricane Helene on these sites is a high priority, and can help us understand the impacts of the storm on the river.
It's a warm Wednesday in June, and staff from the three offices are gathered at the first of multiple reintroduction sites on the river to survey for freshwater mussels. Impacts from the flood are obvious. Banks have shifted, and the trees that once covered the river islands are now gone, knocked down and swept away by the flood. A side channel that was once home to a large number of mussels remained devoid of water for several months, with the flow blocked by a large log jam.
Yet at this site, hope remains. Even in sub-par survey conditions, 7 species of freshwater mussels were found, including the Pocketbook, Spike, Wavy-Rayed Lampmussel, and Tennessee Pigtoe. Several of the mussels were also found gravid, meaning the females contain glochidia (the larval stage of freshwater mussels), ready to be released into the water column above to find a host fish and begin their lifecycle. Additionally, gravid Oystermussels, a rare species, were found displaying in the river.
The next day, a smaller crew went to survey another TWRA reintroduction site, located approximately one mile upstream. At this site, things appear much more grim. The river shifted the location of some of the islands, and large swaths of the site appeared to be made of newly deposited substrate. That means that most likely the substrate (including any mussels in it) were washed away or destroyed by the floodwaters. Only one live mussel was found at the site, a kidneyshell that was in poor health. In addition to the kidneyshell, several shells of rare mussels were found in a portion of the site that experienced less substrate turnover. The less impacted location at the site was harder to survey, with swifter and deeper flow than the previous site. Additional follow-up surveys will be conducted in the late summer or early fall, when the flow is lower, to get a better idea of the mussel populations at this site.
Survey work in the Nolichucky River will continue throughout the summer and fall, visiting native sites and additional reintroduction sites, working to understand the impacts of Hurricane Helene on the freshwater mussels of the Nolichucky River. This will help guide future conservation and management focuses for the Nolichucky, helping to restore the river to its former glory.
