Through my swim mask, I could see what Wendell Haag’s finger was pointing at two feet below me on the riverbed. But I couldn’t immediately see that it was alive. It looked like a rock with some kind of grayish goo stuck to it. We were in the South Fork of the Kentucky River, and I was on my hands and knees with my face in the water and my backside in the air—an inelegant pose I had learned from mussel biologists such as Haag. Finally, after a long, dumb stare, I recognized the mussel. It was mostly buried, but it, too, had left its posterior exposed, and the shell was slightly agape. Draped around that dark slit were fleshy protrusions that flapped like pennants in the current. The mussel, called a pocketbook, was fishing for bass.
A bass, it seems, would mistake those protrusions for an edible minnow. It would snap at the lure, whereupon, instead of food, it would get a mouth blast of mussel larvae—thousands of bivalved vampires smaller than salt grains, some of which would immediately latch on to its gills and start feeding on its blood.
When I first learned about this scenario, it caused me to think differently, and with more respect, about the pocketbook. And not just the pocketbook: roughly 300 species of freshwater mussel have been documented in North America. All of them are brainless invertebrates. They spend most of their lives lodged in riverbeds, filtering algae and bacteria from the passing water. Yet they all get fish to spread their spawn, and most deploy elaborate stratagems. Some mussels, like the pocketbook, convince a fish to bite into a lure full of larvae; others first snap their shell shut around the fish’s head and spray their babies into its mouth. The larvae spend several weeks attached to the fish’s gills, metamorphosing into juvenile mussels, then let go and drop to the riverbed. Often—and this is the point of the whole scheme—it will be upstream from where they boarded the fish.
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Freshwater mussels evolved from marine bivalves more than 200 million years ago, colonizing rivers by getting fish to carry their larvae upstream. Marine mussels are the kind many people like to eat. Freshwater mussels are the kind most people don’t even know exist. They live for decades—more than a century in some cases.
But these days the freshwater species are vanishing. Around a tenth of the 300 in North America have gone extinct already, and a third of the survivors are listed as endangered or threatened. That’s more puzzling than it might sound. Even though we’ve stopped building dams that destroy mussel habitat, even though we pollute rivers much less than we used to, most mussel populations have continued to decline. Scientists aren’t sure why. “There’s this environmental catastrophe going on, and we really don’t know what’s causing it,” Haag said.
Haag belongs to a small community of researchers who are trying to stop it. In a half dozen state-run laboratories around the Southeast, the world hotspot of mussel diversity, researchers have perfected techniques for breeding rare mussels in captivity and then releasing them into rivers. For his part, Haag is leading a 13-state study of some 90 streams to look for the cause of the “enigmatic declines,” as he calls them. There is still reason to hope, he thinks, that the drop-off can be reversed.
Last summer I plunged into four different Kentucky rivers with Haag, a U.S. Forest Service stream ecologist in Frankfort. He took me first to a stream that had so far been spared a serious decline—the Rolling Fork, on the southern edge of the Bluegrass region—to show me the kind of mussel population that was still common back in the 1980s, when he chose his path in life. Sprawled in that shallow river, even I was able to find six different species in a square yard of riverbed. Haag found many more. “We’re walking on mussels here,” he said.
Muskrats are even better mussel hunters than Haag, and on a gravel beach shaded by sycamores, they had left us an assortment of empty shells. Within 20 minutes Haag picked up more than 20 species. There were spikes, washboards and threeridges; muckets and fatmuckets (“not to be confused,” he noted); pimplebacks, pocketbooks and Wabash pigtoes. They ranged in shape from ovoid to almost triangular, in texture from smooth to rippled and pimply. The largest was a six-inch-long washboard—a species that can reach the size of a dinner plate.
“There’s this environmental catastrophe going on, and we really don’t know what’s causing it.” —Wendell Haag, U.S. Forest Service
On the outside the shells were the colors of submerged rocks, from darkest brown to tawny to greenish yellow. But the inside was lined with lustrous, otherworldly mother-of-pearl. It shimmered in the sun. In some shells, it was pure white, in others pale yellow or pink, and in one slender young spike it was a deep, luxurious purple. That startling beauty has no known purpose, Haag said. Nothing sees it when the mussel is alive.
In all of Europe, there are only 16 species of freshwater mussel. But that one stretch of the Rolling Fork harbors about 35. “When you walk down to a riverbank and get in, that’s what you ought to see,” Haag said as we drove away.
That’s not what we saw the next day at Horse Lick Creek on the Cumberland Plateau. In the late 1980s, when Haag first went to Horse Lick, it had dozens of mussel species, too. Now, after searching for more than an hour in sparkling riffles and deep, shaded pools, we found not a single mussel, alive or dead. Haag wasn’t surprised, but he still seemed unsettled. “It’s almost impossible to believe there were ever mussels here,” he said. “There’s just no evidence of them—I question my memory.” But data confirm their disappearance.
Mussel biologists “all wrestle with this sense of loss and tragedy,” Haag told me. Todd Amacker, the Tennessee Valley Authority (TVA) biologist who first hooked me on mussels, once traveled all over the Southeast to take photographs of extinct mussels in museum collections; his poster of 23 of them now hangs in classrooms around the region. “For me, studying life isn’t just about science,” Amacker says. “It’s about appreciating beauty and facing the weight of what we’ve lost.” In 2017 David Strayer, a freshwater ecologist at the Cary Institute of Ecosystem Studies in New York State, wrote a paper called “What Are Freshwater Mussels Worth?” It lists every conceivable reason we might have for valuing mussels. Between the lines of dispassionate philosophical analysis, you can almost hear the suppressed anguish.
The answer to Strayer’s question used to be simpler: Freshwater mussels once had direct economic value. Native Americans ate them in large quantities and used the shells as hoes and scrapers. European Americans never developed a taste for them—the flavor, Haag reports, ranges from insipid to downright foul—but from the mid-19th century on, they did dig up mussels by the thousands on the off chance that one might contain a valuable pearl.
Those “pearl rushes,” however, were nothing compared with the mussel boom unleashed by Johann Boepple, a button maker from Germany. Boepple discovered he could cut many beautiful buttons from the mother-of-pearl in a single large mussel shell. In 1891 he set up shop in Muscatine, Iowa, next to rich mussel beds in the Mississippi River. Within a decade the town had dozens of button factories, and the boom was spreading up and down the Mississippi and its tributaries. In his 2012 book North American Freshwater Mussels, Haag estimates that at least 11 billion mussels were made into buttons between 1895 and 1950. Until cheap plastic buttons put an end to the slaughter, our grandparents and great-grandparents all wore bits of mussel shell on their chest. Mussels certainly had a clear value then.
Surprisingly, Haag concludes, the button industry did little permanent damage; when mussels got scarce in one bed, the “shellers” moved to the next, and eventually mussel populations recovered. We did much greater harm to mussels unintentionally. Above all, it was the 20th-century boom in dam building that permanently devastated mussel populations in the Southeast and all over the U.S.
Dams converted the Tennessee, Cumberland, Ohio and Upper Mississippi Rivers into chains of lakes. Although some mussels live in silty lake bottoms, most prefer shallow, gravelly riverbeds, and the dams destroyed hundreds of miles of prime habitat. Muscle Shoals, Ala., famed for its recording studios, is probably named (with a misspelling) for a 50-mile stretch of the Tennessee River that was once home to at least 70 species of mussel. Fewer than half remain because the shoals are gone, inundated by three TVA dams built in the 1920s and 1930s. Haag estimates that dams are responsible for around 20 of the 30 or so extinctions that befell the mussel fauna of North America in the 20th century.
Why should we care? For one thing, mussels are keystones of the ecosystem. They filter food from the water and transfer waste to the sediment, where it feeds myriad other organisms. Mussels themselves are eaten by fish, mammals such as muskrats and raccoons, and ducks and other birds. For another, a healthy mussel population benefits us indirectly. It has been calculated that the mussels in one 300-mile stretch of the Upper Mississippi filter more than 14 billion gallons of water a day, about 75 times as much as the Minneapolis–Saint Paul sewage-treatment plant. If we still had precolonial mussel populations, all rivers in the East might be much clearer and perhaps cleaner than they are today.
One problem with valuing mussels primarily for their water-cleaning prowess, Strayer points out, is that zebra mussels, an invasive species, are even better at it. In the Hudson River, where Strayer works, they completely replaced native freshwater mussels (to which they’re not closely related). The water got clearer. But biologists, and presumably most of the rest of us, would prefer to keep the native fauna. The Endangered Species Act (ESA) of 1973 requires us to try.
Half-buried in a streambed, mussels look so much like rocks that for an amateur they can be hard to recognize: you look for the slightly open shell pumping water. But they come in an astonishing variety of shapes, sizes, textures and decorative coloring. Two invasive species, beautiful in their own right, aren’t closely related to native mussels. Asian clams may be behind their ongoing decline.
blickwinkel/Alamy (wavy-rayed lampmussel); LaSalle-Photo/Getty Images (Eastern lampmussel, zebra and Eastern elliptio); Ryan Hagerty/FWS (pimpleback); Brittany Barker-Jones/FWS (Coosa moccasinshell); FWS (Texas fatmucket); Ryan Hagerty/FWS (Southern pigtoe); Jamaludin Yusup/Getty Images (Corbicula fluminea)
In the end, the most solid basis for valuing mussels is not what they do for us but what they are, in all their strangeness—their “existence value,” as Strayer calls it. In Bear Creek in northwestern Alabama, Amacker showed me two large mussels, a pocketbook and a pink heelsplitter, that were on the move, passing each other in opposite directions. Their motion itself was barely visible—mussels move by extending a muscular foot and then hauling themselves forward, maybe a quarter of an inch at a time, with long rests. But these two mussels, as they pushed aside cobbles half their size, had left visible wakes in the gravel. Where were they going so effortfully, and why? Mussel biologists can’t answer such questions yet. Mussel research really started in earnest only after the ESA.
People who devote themselves to these obscure creatures have “existence value,” too, it seems to me—they’re a credit to our species. Amacker told me about a postal worker named Herbert Athearn in Cleveland, Tenn., who spent his spare time collecting mussels all over the Southeast, meticulously documenting where he had found them. Eventually, as two marriages fizzled, he filled his entire small house with museum-quality cabinets full of mussels. Before Athearn died, in 2011, he turned this “Museum of Fluviatile Mollusks” over to the North Carolina Museum of Natural Sciences. There, Amacker told me, it has become invaluable to mussel biologists. “When he was collecting in the 1950s, 1960s and 1970s, that’s when things were winking out,” Amacker said. “If it weren’t for him, we wouldn’t know a species had been there.” In other words, scientists wouldn’t know what needs to be restored to any particular stream.
When Haag was in college, in the mid-1980s, he spent two summers working for the Kentucky State Nature Preserves Commission, surveying rivers for mussels. By then dams had eliminated many species from the Cumberland, and Horse Lick Creek—which flows into the Rockcastle River, an undammed tributary of the Cumberland—was known as a refuge for some of them. But Haag noticed even then that most of its mussels were old. By the 1990s they were dying off. “That was mostly complete by 2005,” Haag says. “I watched it happen. I documented it.” It was happening in the Rockcastle as well and throughout the Southeast, especially in smaller upland rivers.
What was causing the declines? Dam building had pretty much stopped by the mid-1980s, and rivers in general had been getting cleaner since passage of the Clean Water Act of 1972, which put limits on sewage and industrial discharges. Nor did climate change seem to be a likely cause: it’s not clear whether the rivers in question have warmed much, but warmer temperatures generally make mussels grow faster.
Of course, even with the Clean Water Act, many streams are still polluted. Fertilizer and pesticides run off farm fields; heavy metals seep from open coal mines. Rains erode soil from farms and construction sites, burying streambeds in sediment. The conventional wisdom has been that some combination of such factors must explain the continuing decline of mussels. But there have been few data to back that assumption up, Haag found.
That’s actually a hopeful sign: it means mussels aren’t simply doomed by modernity.
In the Rockcastle River, where the decline had been blamed on coal mining, Haag had an epiphany one day. As he searched for mussels, he was brushing away bunches of Asian clams, Corbicula fluminea. An invasive species, they were a familiar nuisance: he’d encountered them throughout his career in almost every streambed. After first being reported in Washington State in 1938, the clams had spread cross-country; they’re now in 47 states. Greenish-yellow and small, typically an inch or less across, they can get so abundant they clog water intakes at power plants. Concentrations in the thousands per square yard are not uncommon.
“I remember lying there in the river,” Haag told me as we drove away from the Rockcastle last summer, “and just all of a sudden I thought, ‘Wow, why have we been ignoring these things all along?’ They’re so abundant. How could they not have had any effect on the native biota?” As a graduate student at the Ohio State University, Haag was diving regularly in Lake Erie when zebra mussels arrived in 1988—and in short order cleared the murky water. “Suddenly I could see a long way,” he recalls. But the invaders also cleared the lake of native mussels. Haag thinks Asian clams might have had a similar impact as they spread across the Southeast in the 1960s. Back then, though, there were few mussel biologists around to notice.
In 2018 Haag and his colleagues did an experiment at 17 sites in the Rockcastle and its tributaries. That June they put juvenile, captive-reared mussels on the streambed, caged inside small concrete silos that water could flow through. They tested the water quality repeatedly through the summer, and at the end, after they returned to collect the mussels, they measured the abundance of Asian clams. At some sites the mussels had fared poorly, growing much less than at others. Cold water slowed growth, but there was little evidence of contamination by coal mines and no evidence that the slower growth was connected to water chemistry. Instead it was strongly correlated with the abundance of Asian clams.
Haag is now following up on that study with a much larger one—the most comprehensive attempt yet to get to the bottom of mussel declines. He and his colleagues spent three summers collecting data at about 90 streams in 13 states from Minnesota to Georgia. Researchers in all the states volunteered their help. Erin McCombs, a mussel biologist who now works at American Rivers, an environmental group based in Washington, D.C., secured the funding for the $1.3-million study from the BAND Foundation, the Merck Family Foundation and federal agencies.
This time, in addition to putting out captive-reared baby mussels, Haag’s team assessed each stream’s existing mussel community. They measured the prevalence of algae, the influx of sediment, and other variables that might affect mussels. From state researchers, they gathered data on water chemistry and on the health of each stream’s fish and insect communities.
Haag is still parsing the vast dataset. It may not yield a conclusive answer to the mystery of mussel declines, he warns. But he thinks none of the usual suspects, such as pesticides and excess sedimentation, will emerge as likely culprits. So far the only factor that seems to be present in all or most streams hit by enigmatic declines is C. fluminea. “I’m pretty confident it’s Asian clams,” Haag says. When they first invade a stream and then explode in population, they might suck so much food out of the river that young mussels can no longer grow.
There’s another possibility: the clams might transmit a novel virus or other pathogen. The idea has been in the news in recent years. Since 2016 the Clinch River in southwestern Virginia has been struck repeatedly by sudden mussel die-offs in which thousands of pheasantshells expire within weeks. In 2020 University of Wisconsin–Madison veterinary epidemiologist Tony Goldberg and his doctoral student Jordan Richard identified a novel virus in some of those dying mussels. It turned out to be a false alarm. The virus soon turned up in other rivers; it seems to be an opportunist that affects mussels that are already sick for other reasons. “We still don’t know what’s killing the mussels” in the Clinch, Goldberg says—or how such short-lived catastrophes might relate to the longer-term declines Haag has been investigating.
Goldberg and Charlotte Ford, a postdoctoral researcher in his lab, are now analyzing baby mussels from Haag’s study. So far they haven’t found a mussel killer. But they have confirmed mussels’ essential strangeness: instead of fighting viruses, as vertebrates do, mussels seem to try to make peace with any that come their way. The researchers have found DNA of some 7,000 previously undocumented viruses in the mussels, almost all of them novel—“which is a staggering number,” Goldberg says, “and very difficult to analyze.”
Whatever the cause of mussel declines, it’s something specific to them—that much is already clear, Haag thinks. It’s not just that we’ve degraded mussel habitat in 1,000 ways. If that were the problem, then mussel health in a stream would be correlated with that of fish and insects, each of which is used as an indicator of a stream’s biotic integrity. But “that’s not the case,” Haag said. “There’s no correlation whatsoever.”
That’s actually a hopeful sign: It means mussels aren’t simply doomed by modernity. They’re able to live in the world we’ve created—provided, that is, that we can figure out what’s killing them and start restoring the populations that have been lost.
Alabama, where I live, has 181 species of mussels, more than any other state. Of those, 63 are listed as endangered or threatened. At the Alabama Aquatic Biodiversity Center, a state-owned cluster of one-story buildings and a few ponds outside Marion, program supervisor Paul Johnson and his small team try to keep the most critically endangered species of mussels from winking out by hatching them and releasing them back into streams. “Paul is an effing hero,” says Tierra Curry, a senior scientist at the Center for Biological Diversity, an environmental group. “He’s the only reason some species are still on this planet.”
The process begins in the places where the mussels still live, often just a few miles of one small river. Every spring Johnson’s team heads to those places—the Conasauga River in Georgia for the Coosa moccasinshell, for example, or the Buttahatchee River in Mississippi for the Southern combshell—to look for gravid female mussels. Finding any endangered mussel is hard, but finding one that’s pregnant is harder: you have to carefully pry open the shell just enough to see whether the gills are inflated with larvae. In the Buttahatchee last spring, Johnson says, it took four guys searching for half a day to find two gravid Southern combshells. Some years they get none.
At the biodiversity center, I watched biologist Michael Buntin open one of those Southern combshells again and squirt its gills, very gently, with water from a hypodermic needle to flush out the milky larvae. “I don’t want to hurt her,” he explained. (The next day a colleague would be traveling five hours round-trip by car and kayak to take this single mussel back home.) Under a microscope the larvae were translucent, but they were already tiny bivalves. When Buntin sprinkled salt in their petri dish, they snapped shut, proving they were alive—and illustrating how they would shortly latch on to fish gills. “We’re going to make some fish angry,” Buntin said.
In a large hangar that was alive with the noise of pumps and water gurgling into hundreds of tanks, Buntin poured the solution of larvae into a small, clear tank, then dumped in a couple of dozen logperch, the host fish for Southern combshells. Within a few minutes, he said, the fish would all have larvae clinging to their gills. Within a few weeks the larvae would have transformed into juvenile mussels that would drop to the bottom of the tank. For the next year or more they would be nurtured in a series of containers, the last one suspended in the pond out back, until they were big enough to be tagged and released.
Before Johnson’s co-workers even begin to breed a mussel, they have to discover what host fish it needs. That can take years. For one mussel species, they had to try almost 70 different fish. At Kentucky’s state-run Center for Mollusk Conservation in Frankfort, where Haag has his office, director Monte McGregor tells me how he sometimes avoids such hassles. He raises some mussel larvae in vitro in an incubator, feeding them rabbit serum or another substitute for fish blood. He did that with the purple cat’s paw mussel, which had dwindled to scattered individuals in one Ohio creek. With the help of the U.S. Fish and Wildlife Service, McGregor’s team brought as many of those mussels as they could find into captivity, “and then we reared the animals from there,” he says. They’ve since released nearly 13,000 purple cat’s paws into several streams, creating new populations.
Johnson doesn’t have the resources for such techniques. His annual budget is no more than $600,000, less than the cost of a single incubator. Yet he and his colleagues, rattling around a sprawling and aging facility, have established new populations of at least four species of mussels, including orangenacre muckets. Success means showing that the captive-bred mussels are reproducing in the wild. That takes time, not just to breed the mussels but for their babies to grow large enough for biologists to detect them. “It’s a 10-year process,” Johnson says. With Southern combshells, they’ve been trying even longer. Destruction is easier than restoration.
Last fall Haag texted me a video of a mussel he had just seen in Kentucky’s Rockcastle River. I recognized it right away: it was a pocketbook displaying its lure. In parts of the Rockcastle and in a few other streams, Haag said, he’s seeing young mussels again. Some species may be coming back. In those same streams, the Asian clam population seems to have crashed, which may not be a coincidence.
But some species are now so rare that they won’t be able to recover without help. In the fall of 2024 Amacker learned that his aquatic ecology group at TVA had been awarded a $3.4-million grant from the FWS to promote the recovery of six species of rare mussel, with the goal of getting them off the endangered list. Somehow the grant survived the 2025 transition to the Trump administration. The amount is “unprecedented” for mussel folk, Amacker says. Most of it is to be doled out to hatcheries like Johnson’s and McGregor’s.
One day last July I drove out to meet Johnson at Big Canoe Creek, less than an hour northeast of my home in Birmingham. The creek drains into the Coosa River—or rather into Neely Henry Lake, one of a series of reservoirs built by Alabama Power in the 20th century. The dams wiped out more than 30 species of snail and at least three species of mussel, probably more. “You wonder what was lost that never got recorded,” Johnson said. But Big Canoe Creek remained a refuge. Johnson is now trying to reestablish the Coosa moccasinshell there.
He was accompanied that day by Brittany Barker-Jones, the FWS biologist responsible for the species, as well as by some local friends of the creek. One of them, Doug Morrison, manages a 422-acre nature preserve a few miles upstream that opened to the public in 2023. Morrison told me that in 2013 he had helped arrange for the FWS to dismantle an abandoned 19th-century mill dam around 100 yards upstream from where we stood. This stretch of the creek had since become prime habitat again for fish and mussels. All of this work, Johnson told me when we first met a few years back, is about people trying “to reclaim their watershed and improve their corner of the planet.”
We waded upstream into a completely shaded section of the creek. Johnson and Barker-Jones located some tagged mussels they’d released in previous years. The rings on their shells showed that they’d undergone a pronounced growth spurt since leaving the hatchery.
Then we turned to the main task. Johnson and other biologists call it “releasing” mussels—they’re wild animals, after all—but it feels more like planting. Johnson pulled out 322 Coosa moccasinshells in a blue net bag. They were about the size of almonds, shiny and oak-colored with greenish highlights. Barker-Jones carried a tray of them into the creek, followed by Granger Waid, a friend of the creek, and his 10-year-old daughter, Mary Grace. They began to move slowly downstream like sowers in a field, planting one mussel at a time—the biologist in her wetsuit, the dad in his camo hoodie, the little blond girl in her cutoffs.
Johnson and I took a turn, too. The water was rushing and pleasantly cold on that summer day as I dug gently with my fingers into the fine gravel. It was satisfying work—you just had to take care not to wedge the mussels into the streambed upside down, which might suffocate them. “Pointy side up, round side down,” Johnson called out helpfully. Their future was in our hands.
