Elk River Restoration Benefits Rare Mussels

A joyful whoop echoed across the rushing Elk River, where teams of biologists waded in wetsuits.

Todd Amacker, Tennessee Valley Authority aquatic endangered species biologist, held up an empty, gleaming black mussel shell.

“This is an extinct species,” he said, his voice full of wonder.

While this Tennessee riffleshell probably doesn’t live here today – it likely washed free from a very old pile of shells in a muskrat midden – an intact shell is an amazing find.

And during their weeklong survey of the Elk River, the team of biologists from TVA’s Environment and Sustainability group and U.S. Fish and Wildlife Service could expect to find any number of living, extremely rare mussels.

That’s because the Elk was – and is – one of the most biodiverse rivers in the world, even as it’s recovering from more than a century of land and water use that made it hard for water-filtering mussels to survive.

Searching for and recording mussel diversity is especially important now.

Mussel species across the region are still at risk – with eight more long-sought species finally declared extinct after years of searching.

For those animals, decades of impacts upriver - changed flow, sediment runoff and other pollution – were too much to survive.

Scientists hope now to find many rare species in this restored river.

Standing in the water, Amacker turned the riffleshell over and looked wistful. “The poet in me is holding on to a sliver of hope,” he said.

TVA fisheries biologist Justin Wolbert, TVA aquatic endangered species biologist Todd Amacker and TVA aquatic ecologist Matt Reed sift through a river bottom sample from the Elk River in middle Tennessee.

A Tale of Two Critters

The Elk River laps gently at the rocky shore, but in the thalweg – the deepest underwater "valley" within a river – the current gallops along.

Mussels dot the rocky river bottom.

Most are common species.

And many are not.

“There are certain unicorn species here, such as the cracking pearlymussel that’s only found in two places on Earth,” Amacker said. “It lives in the Clinch River and here in the Elk.”

On this day, biologists worked hard, treading underwater to keep their place in the Elk’s clipping current as they piled rocks into the mesh-bottomed sieve at 100 sample sites.

Amacker and Matt Reed, TVA aquatic ecologist, along with Andy Ford, U.S. Fish and Wildlife Service fisheries biologist, moved between teams to identify and measure mussels.

“What do you think this is?” Amacker said. “I have an idea. I want to see if you agree.”

He handed Ford a green algae-furred shell.

Ford considered. “It’s slabby,” he said, running a finger over its ridges. “The slabside pearlymussel has kind of a shelf.”

“You have to close your eyes and feel it,” Amacker said, nodding. “You have to use all your senses sometimes.”

In textbooks, mussel shells may look neat and distinct. But in a river with mussels of different ages and wave-worn patterns, identifying them takes practice and skill.

The biologists ran fingers over the shell and along the edges. They measured its width and length and peeked at the mussel’s foot, the soft tissue barely visible inside the shell.

All signs pointed toward the slabside pearlymussel, an endangered species whose recovery Ford coordinates.

Reed recorded its scientific name, Pleuronaia dolabelloides, on the clipboard and Amacker tucked the mussel back into its riverbed.

“It’s a really important find,” Amacker said.

Mussels found include, clockwise from top left, the rare slabside pearlymussel; the common threeridge; the shell of an extinct Tennessee riffleshell; and the Tennessee pigtoe, Tennessee clubshell and longsolid, all three of which are rare.

Of Mussels and Muskrats

As the hours passed, the sun broke through the clouds. Steam rose from the snorkelers’ wetsuits as they carefully compared mussel shell shapes, colors, sizes and ridges.

“Here’s a suggestion for those who enjoy suffering – go into malacology, the study of freshwater mussels,” Amacker said, laughing. He pointed at mussels balanced on his palm. “These are three different species.”

The shells – quickly keyed out to be Tennessee clubshell, longsolid and Tennessee pigtoe – all had seemingly identical ribbed, whitish shells.

“They’re all similar, related, and highly imperiled,” Ford said. “It’s hard for even experts to tell them apart, especially the relics.”

Relics are old, empty shells – like the extinct Tennessee riffleshell – but they still give critical information.

After the first find, the team discovered another riffleshell, stuffed with mud so it had the right heft and closed hinge to almost look alive.

“Gerry’s going to be so excited,” Amacker said, as he gently whisked mud from the riffleshell with a toothbrush.

The riffleshell relics will go to Gerry Dinkins, curator of malacology at the McClung Museum. The McClung displays the bounty of freshwater mussel biodiversity in the region.

Alive, dead or relic, every mussel tells the story of this river.

“After this quantitative survey along the transect, we’ll do a qualitative snorkel,” Reed said. “(For that), you can go wherever you think there might be something significant.”

Both the quantitative data along the transect and the qualitative results – where biologists can search in likely spots such as the muskrat middens – tell scientists that the Elk’s about to add a new chapter to its story.

Marley Machara and Santiago Martin, U.S. Fish and Wildlife Service biologists, are key partners in mussel recovery.

For Whom the River Flows

As much as the Elk has changed over the past century, it will change again with the removal of Harm’s Mill Dam just over one river mile upstream.

Harm’s Mill isn’t a power-generating dam. It was a privately owned dam that the Tennessee Wildlife Resources Agency purchased so they, along with TVA and member organizations of the Tennessee Aquatic Connectivity Team, could remove the dam and restore the river.

That will benefit the mussels, fish, insects and other creatures that live in the Elk River.

“It’ll help anything that likes more free-flowing ecosystems,” Justin Wolbert, TVA fisheries biologist, said. “A free-flowing ecosystem allows food to come through the system – insects and fine particles of decomposed leaves that those insects eat.”

“He’s talking about the base of the food chain, from insects up,” Reed said.

“And fish have adapted to those insect communities for millennia,” Wolbert said.

Reed nodded. “Everything’s interconnected. If the fish can’t disperse, then it not only impacts them, but also the mussels that use them as hosts."

That’s because while mussels themselves, anchored as they are on the river bottom, can’t move, their young can – with the help of migratory fish.

Mussels spray their tiny larvae, called glochidia, into the mouths of host fish. The migrating fish then carry them upstream and downstream.

After Harm’s Mill Dam comes out, big-river fish, including the endangered boulder darter, will again be able to migrate and find new mates, helping genetic diversity.

Mussels will be able to move more over generations and the river itself will be able to flow more naturally, depositing rich sediment along its banks and feeding fish communities with swarms of good bugs.

“Taking out an impoundment like that, it’s almost impossible to quantify the beneficial impacts,” Reed said.

TVA’s Zach Luttrell and Anderson Smith record mussel data from a near-shore sample.

Great Expectations

As day one of the survey wrapped up, thunderstorms moved in. The crew waded to shore, hurriedly packing clipboards and boxes before the clouds unleashed torrential rains.

Their survey work would continue all week – a last look at the river before the dam removal.

Afterward, crews from TVA, the Tennessee Wildlife Resources Agency and Fish and Wildlife Service would be back.

While mussels in the Southeast are still at risk, biologists are optimistic about the Elk, especially with the river connectivity that’s to come.

“Something’s going on here,” Ford said. He gestured to his datasheet filled with a list of rare species. “It’s a rebound. This is a really good day.”

Photo Gallery

Andy Ford, U.S. Fish and Wildlife Service fisheries biologist, and TVA’s Amacker identify similar rare mussels on the banks of the Elk River.

TVA and the U.S. Fish and Wildlife Service partner to research and restore mussels throughout the Tennessee Valley region.

Reed records key data about mussel locations, species and measurements.

TVA’s Cory Chapman and other team members don wetsuits and snorkel gear to find mussels attached to river rocks underwater. 

Each river survey includes 100 samples taken at precise distances along a transect, or line, into the water. Clockwise from top left, Martin and Machara, Ford and Reed, Reed and Wolbert and Amacker and TVA aquatic zoologist Aaron Coons carefully collect samples.

PHOTO AT TOP OF PAGE: Many mussels, such as the rare shiny pigtoe that Amacker holds, call the Elk River home.

Members of the Tennessee Aquatic Connectivity Team include TVA, the Tennessee Wildlife Resources Agency, U.S. Fish and Wildlife Service, The Nature Conservancy, National Fish and Wildlife Federation and Conservation Fisheries, Inc.  

TVA biologists and their partners found a multitude of rare mussels that live and breathe in the Elk River, including: 

• Threatened longsolid
• Threatened rabbitsfoot
• Proposed endangered Tennessee clubshell
• Proposed endangered Tennessee pigtoe
• Endangered slabside pearlymussel
• Endangered snuffbox
• Endangered shiny pigtoe
• Endangered cracking pearlymussel