Armed with snorkels and Super Glue, a group of scientists ventured into the remote mountains of North Carolina this fall.
Their aim? Re-establishing rare mollusks inside the Nantahala National Forest.
Super Glue is what biologists at the North Carolina Wildlife Resources Commission used as part of a Tuckasegee River homecoming for 4,600 Wavy-rayed lampmussels—mollusks that haven’t been seen in the stream in more than a century.
The glue is the secret stick-em that secures personalized tags for the 2-year-old animals the commission raised inside the state fish hatchery. It allows the group to track the mollusks’ health and population over time, helping ensure the cleanliness of rivers and streams.
You see, according to Matt Reed, an aquatic ecologist with Tennessee Valley Authority, a single mussel can filter up to 8 gallons of water every day. It’s why, he said, biologists like to call them “the livers of the rivers.”
“Mussels provide a whole suite of ecosystem services,” Reed said. “A healthy mussel bed is akin to a coral reef in the ocean.”
This is why the work he and other biologists are doing to raise and then re-introduce mollusks to their original watery homes is important.
The challenge in establishing healthy communities of mollusks is that they have become so rare that biologists often have to start from square one.
“In a perfect world, we’d be able to translocate mussels from one source to another,” state biologist Luke Etchison said. “Propagation is like your Hail Mary for conservation. You have to propagate when you don’t have enough in the wild to move directly.”
According to Etchison, raising mussels in a hatchery starts by introducing a few fertile female mussels to a host fish, such as largemouth bass. As part of the mussel’s reproduction cycle, the female opens her shell and displays an artificial lure that looks like a wiggling minnow.
Once the bass strikes the lure, the female mussel discharges thousands of glochidia into the fish’s mouth. The glochidia attach to host fish by siphoning blood from the bass gills until each individual is mature enough to strike out on its own.
Nature’s process usually takes a few weeks, but once the microscopic mussels drop, the host fish are returned to the wild unharmed, and hatchery biologists move the fresh crop of mollusks to a series of sand-filled livestock pans.
Each rubber bowl is linked to a series of pipes that creates a free-flowing aquarium for the mussels to grow until they are large enough to hold a blob of Super Glue and a tag.
The tags are color-coated and numbered so biologists can monitor the lifecycle of each mussel after they are introduced into the wild.
If a biologist finds the mussel in a later survey, the information on the tag will allow researchers to correctly identify the age of the individual as well as the parents from which the animal originated. By counting tags, future surveys will indicate the success of that year’s hatch.
The team expects a survival rate of 30%.
“If a third of the mussels we’ve stocked go on to have successful reproductive years, they’ll be able to blanket the riverbed pretty quick,” Etchison said.
The cost to raise a single mussel in a hatchery can range from $5 to as much as $30,000, depending on the number of mussels that survive to taggable size.
Propagation is a labor-intensive venture that has a high probability of failure because of the constant attention each mussel requires during its two-year incubation period.
If the water stops or the system is contaminated, a whole crop of mussels can be lost. Even if everything goes well, successfully propagating a class of mussels can be challenging, especially for federally endangered species like the Appalachian elkton.
Since 2012, the Marion State Fish Hatchery has raised 5,229 Appalachian elktoe mussels to taggable size. Out of nine attempts, the odds of successfully propagating the species have been limited to 22%, with a total cost of $52 per mussel.
“There are just so many different things that can happen,” Etchison said. “Early this year, we tried again. We put all this effort into getting the host fish and trying to propagate them. We got some juveniles to drop off, but they ended up all dying.”
Etchison and his team have seen better results with the Rainbow mussel, yielding 24,016 taggable Rainbows with a success rate of 67%.
The price tag: is $11 per mussel.
Although expensive, the costs and long odds of the successful hatch are risks the Commission, Tennessee Valley Authority, and Eastern Band of Cherokee Indians believe are worth taking.
Their work is part of the Little Tennessee Native Fish Conservation Partnership, which is a coalition of state, federal, and non-profit partners whose mission is to promote and preserve biodiversity throughout Little Tennessee River Basin— the nation’s listed Native Fish Conservation Area.
“Partnerships such as these are key to implementing conservation efforts across the Valley,” said Rebecca Hayden, director of TVA’s Natural Resources. “TVA has been a member of the Little Tennessee Native Fish Conservation partnership since it was initiated, providing support for projects that protect and improve aquatic biodiversity. We are proud to be a part of the partnership and help with the propagation and reintroduction of native mussels back in the watershed.”
Large congregations of mussels attract food for aquatic fauna and provide habitat for both game and non-game species of fish to spawn. Plus, with a healthy bed of shells on the river bottom, they stabilize the substrate and prevent erosion.
It’s a secondary filtration benefit that protects an entire ecosystem from pollution.
“Every stream we have that has a lot of mussels tends to be the best place for fishing, swimming, and general recreation. It’s all tied together,” Etchison said. “Recovering the mussels is part of a bigger picture of making a stream swimmable, drinkable, and fishable.”
And that’s a big deal, considering mussels are the water filters to a $375 billion outdoor recreation industry that supports nearly 2% of the U.S. gross domestic product.
“Look at the Duck River in Middle Tennessee. It’s no coincidence that the most biodiverse stream in North America has got the largest population of freshwater mussels,” Etchison said. “Put it this way... there’s so many in there that I wouldn’t want to walk barefoot in it.”
The good news is that the Little Tennessee River Basin is home to its share of heel-splitters, too.
The White heelsplitter and the Tennessee heelsplitter are among Little Tennessee’s remaining 30 native species of freshwater mussels—a dozen of which are listed as rare, threatened, or endangered by federal or state agencies.
These species include the Appalachian elktoe, Slippershell, Spike, Tennessee pigtoe, Long-solid, Wavy-rayed lampmussel, Tennessee heelsplitter, Littlewing pearlymussel, Tennessee clubshell, Fluted kidneyshell, Purple lilliput, and Rainbow.
Reed says the shortlist of struggling mussel species in the Little Tennessee River Basin is a footnote to a greater problem.
In the past 120 years, 26 North American mussel species have been wiped out due to extinction—all of which were native to southeastern streams.
Of the 275 species that remain, he says more than two-thirds are at risk.
“Over the last century, we’ve seen stark declines in mussel populations,” Reed said. “Sedimentation from urban development, construction, big ag, mining, and logging are all things that have negatively impacted the area’s biodiversity.”
However, through Clean Water Act policies, conservation efforts, and improved industry practices throughout the U.S., biologists like Reed are now seeing a return of habitat that can support the region’s biological treasures for years to come.
It’s why the Little Tennessee Native Fish Conservation Partnership is working to help species that are teetering on the brink of extinction.
“Mussels are the canaries in the coal mine. They’re the first to go,” Etchison said. “If mussels are all that’s missing, but everything else has recovered, we think it’s time to bring them back.”
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