Get to Know the South’s Mighty Mussels

If you think a freshwater mussel is little more than a rock with gills that sits sedentary on the bottom of a stream, let Paul Johnson disabuse you. “Mussels are very, very far from boring,” says the Alabama Aquatic Biodiversity Center (AABC) malacologist (that’s someone who studies mollusks). “Things get very weird, very fast.” Johnson should know; he’s spent his career helping to demystify and conserve mussels, which are not only among the country’s most crucial cleaners of waterways, but are also its most endangered group, period.

All of their weirdness ends up in service of water filtering. For starters, each mussel has a “foot,” a muscular organ extending from its shell that it uses to maneuver. Reproduction gets even stranger. Mussel larvae, called glochidia, need a way to disperse, so many hitch rides on a host fish—but only after their mother attracts the fish by extending a “lure,” which might look like a minnow or a worm, tailored to entice specific species. When the fish approaches, instead of a snack it gets a faceful of Pac-Man-shaped larvae, which embed themselves into the host’s gills as tiny parasite passengers until they’re ready to drop off and find their own patch of stream bottom. Then they’ll spend their long lives—some live up to a hundred years—taking in water, filtering out organic particles with their gills, and then expelling the water.

Mussels were once so plentiful that Johnson describes their output as “damn near turning over entire rivers in volume.” And the South still has more species than anywhere else in the world. Thanks to the diversity and sheer number of ancient rivers and streams here, hundreds of unique mussels evolved in the region, often tied to a single watershed and sometimes even a single host fish species. Alabama alone claims more than 180 species. But due to the usual suspects of pollution, development, and damming, many of the vital little bivalves are in danger of blinking out. In 2023, six species were declared extinct in Alabama; nearly sixty more there are listed as threatened or endangered.

That’s where Johnson and his team come in: At their Marion lab, they bring in rare mussels from the wild to piece together the secrets of their lives, starting with discovering their host fish. Once they do, the team nurtures the expelled larvae that ensue until they grow into mussels big enough to return to streams and rivers. That process takes years—and then perhaps another decade-plus for them to become self-sufficient. “It’s not a quick fix,” Johnson admits. Still, his lab has worked with some forty species and restocked untold thousands of mussels into rivers region-wide, carefully marking each shell to monitor the populations. Five of those species, including the pale lilliput, the orangenacre mucket, and the oyster mussel, now boast reproducing wild populations.

Mussel work goes hand in hand with river restoration—the Nature Conservancy and the U.S. Fish & Wildlife Service, among others, partner with the AABC to get waterways up to snuff to support the reintroductions. “In the end, if you target the itty-bitty mussels, you protect the whole river, too,” Johnson says. “The incredible diversity of freshwater mussels here is a reflection of the magnificent natural history of the Southeast.”

1. Coosa Moccasinshell

An eight-mile stretch of the Conasauga River in Tennessee holds the last population of Coosa moccasin-shells. Since so few remain in the wild, Paul Johnson is carefully growing batches of them at the Alabama Aquatic Biodiversity Center lab for reintroduction to select tributaries of the Cahaba and Coosa River basins.

2. Appalachian Elktoe

In 2024, Hurricane Helene nearly drove the green-striped, neon orange–footed Appalachian elktoe to extinction, and biologists are still rescuing survivors from streams to propagate in a North Carolina hatchery—highlighting the risk of one catastrophe causing a species already on the brink to vanish completely.

3. Shinyrayed Pocketbook

The genus of this species, Hamiota, means “female fisher.” Like its close relative the orangenacre mucket, the shinyrayed pocketbook extends a long strand of mucus, at the end of which two “minnows” appear to dance in the current to attract the host fish. Once, this federally endangered mussel existed all over the Apalachicola River basin; today only about ten wild populations remain.

4. Fanshell

Only one population of the fanshell is hanging on in Alabama, at the twenty-five-foot-deep bottom of the Tennessee River at Muscle Shoals, making the individuals difficult to find. To attract their host fish, the females put out what Johnson calls a “downright wacky” lure that looks like a bloodred worm.

5. Southern Combshell

Just twelve miles of habitat in Mississippi’s Buttahatchee River still hold Southern combshells, which once thrived throughout the Mobile River basin. Last year, Johnson’s team introduced 3,500 specimens into three watersheds in hopes of establishing new populations.

6. Wavyrayed Lampmussel

This Tennessee River basin species is as charismatic as a mussel gets—a single female can produce offspring with two different types of lures, one that looks like a fish and another that resembles an aquatic insect, to attract the host fish: largemouth and smallmouth bass.

7. Orangenacre Mucket

Johnson and his team spent years propagating and establishing a reproducing population of orangenacre muckets in the Locust Fork of Alabama’s Black Warrior River watershed after they went extinct there in the 1970s. In total, only twelve pockets of these female fishers remain in their once widespread range.