Mystery of the Mussels
Rare Species Restored to Region’s Watersheds
Is it possible to bring animals back from the brink of extinction?
Yes, a team of Tennessee Valley Authority scientists and their partner agencies found, after they helped the endangered snail darter recover.
But is it easy?
Work to restore the federally endangered pale lilliput and Alabama lampmussel took time, funding, collaboration and experimentation.
And above all, a lot of work.
TVA scientists Shannon O’Quinn, a senior water resources specialist, and Todd Amacker, an aquatic biologist, partnered with the Alabama Department of Conservation and Natural Resources and other agencies.
Their goal? Restore the endangered mussels to priority watersheds such as the Duck and Paint Rock rivers in Tennessee and Alabama.
“If you want to see the greatest number of freshwater mussel species on planet Earth, you’d come to the American Southeast,” Amacker said. “But some of these (species) have already gone extinct.”
Thirty mussel and 60 snail species are gone forever.
“Yet there’s still a tremendous amount of diversity that we can save,” Amacker said. “And the time to act is now.”
‘Livers of the Rivers’
The story of the mussels goes back to the 1930s. It isn’t so mysterious, after all.
Many mussels vanished because the very first TVA dams prioritized flood control and power generation.
This was vital. The dams were – and are – highly successful. They saved human lives and produced power for one of the poorest regions in the nation.
Yet there was a downside.
Water that the dams released was too cold for many native river species, mussels included, O’Quinn said. The flow and physical habitat also changed.
And that mattered.
“Mussels are the livers of the rivers,” Amacker said. Mussels constantly filter water and keep it clean.
"That’s water that humans drink, water that humans boat, swim and fish in. And it’s water that we depend on to sustain aquatic biodiversity.”
People need mussels. And to save them, TVA is creating habitats in which they’ll thrive.
Creating the right habitat meant first changing how TVA managed rivers.
In the 1990s, the Reservoir Release Improvement Program meant that, for the first time, biologists worked hand in hand with dam operators and river managers.
Biologists monitored dissolved oxygen levels and temperatures of tailwaters below dams.
And dam operators and river managers built weirs, added liquid oxygen and controlled water releases so not too much cold water rushed out at once, yet there was always enough water flowing for good habitat.
“Those changes more closely mimic how a natural river behaves,” Amacker said.
Today’s river management also meets local economic and recreation needs. With cold water right below the dam and warmer water in the reaches downriver, trout fisheries and native species can flourish.
“Now, we strive to satisfy both uses,” O’Quinn said.
Fussing Over Mussels
With the river habitat in place, scientists turned to the animals that belonged there.
In the case of the pale lilliput and Alabama lampmussel, that meant finding out which fish were their hosts.
Hosting isn’t as nice as it sounds. All mussels trick fish – or salamanders, in some cases – into helping them raise their young. To do this, they blast their larvae into a fish’s mouth.
They all have different methods of tricking a fish into saying “ahh.”
One type of mussel disguises her larvae as aquatic insects. Another lures a fish close then clamps down on its head. A third tethers a long mucus tube to her shell, hoping fish will nibble the shimmering, larvae-speckled slime waving in the current.
But Amacker’s favorite fish trickster is the wavy-rayed lampmussel.
“I think it’s the best story in nature,” he said. “And I’ve watched David Attenborough all my life, so that’s saying something.”
When a mother lampmussel is ready to reproduce, she anchors herself in the river bottom. She wiggles part of her body called a mantle. Like an angler’s lure, it looks just like a fish.
“It’s pretty impressive,” Amacker said. “It has eye spots, a fake dorsal and caudal fin, fake pigmentation.”
A hungry fish sees what it thinks is a tasty minnow, opens its mouth wide and strikes.
“At the last minute, (the mother mussel) will suck in her mantle lure and spray thousands of baby larval mussels, called glochidia, into (the fish’s) open mouth,” Amacker said.
No matter the method to lure the fish, the baby larval mussels then encyst, or implant, themselves into the fish’s gills. They feed on the fish’s blood for a few weeks. Then they’re old enough to drop off and begin life on the stream bottom alone.
This is a key step in a mussel’s life cycle.
Through careful observation and experimentation, biologists at the Alabama Aquatic Biodiversity Center discovered that the studfish was the unwitting host for the pale lilliput.
Over several years, beginning in 2016, scientists collected studfish and mussels. They brought them to the lab and hoped the animals would cooperate in their strange interspecies dance.
When it worked, they cultured – reared – the young for several years until they were large enough to be released.
The process is slow and painstaking, but worth it.
“These partners are true conservation heroes,” Amacker said. “This is a conservation success story.”
Before the project, the pale lilliput and Alabama lampmussel were two of the rarest mussels on Earth. Biologists knew of them only in one tiny tributary.
Yet now, they’re on their way to recovery.
“Both those species are now found outside of that stream,” Amacker said.
And that’s not all.
“They’ve been successfully reintroduced to several streams outside the Paint Rock River system, and they’re doing well.”
The story would be incomplete without talking about watersheds themselves.
A watershed includes everything that feeds into a river – tributaries branching in and the farmlands, forests and grasslands surrounding it over which rainfall flows.
TVA and its partners chose their priority watersheds – which include the Duck, Paint Rock, Bear Creek, Little Tennessee, and the Clinch and Powell rivers – by considering which ones provided the best mussel habitat already.
Then they enhanced these habitats, working in the water and on the shorelines.
“We’re working with partners to put projects on the ground,” O’Quinn said. “Reduce sedimentation. Establish riparian buffers. Remove aquatic barriers.
“You have to make sure the habitat you’re reintroducing (the mussels) into is suitable for them to survive and re-establish.”
This can help species on the brink of extinction have a better chance of survival – very important after all the time and work to raise them. It can prevent others from reaching that critical point. And it stretches species recovery dollars farther.
The success of the pale lilliput and Alabama lampmussel – and others introduced throughout the Valley – is not only a win for them.
It’s also a win for people.
Clean, flowing, biodiverse river ecosystems make the Valley region a better place to live, work and play, whether you’re a human or an animal.
“On a global scale … these are special places,” Amacker said.
Learn how TVA specialists monitor conditions in the region’s waterways at the TVA Water Quality page.