In Kentucky’s rivers, researchers try to understand where the mussels have gone

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Written by Liam Niemeyer for Kentucky Lantern

Wendell Haag wades through the cool, moving water of the Licking River, his eyes scanning across the silty bed for the distinctive shells he’s studied for decades. 

The river is seemingly paved with the shells of freshwater mussels featuring various sizes, colors and species, buried into the sediment amongst the rocks, crayfish and minnows. Kentucky is one of the most diverse places in the world for these mussels, with the state being home to more than 100 species — about a third of all species of North American mussels. The Licking River in particular is an epicenter for these creatures to thrive with more than 50 species of mussels on its own. 

Haag, a research fisheries biologist with the U.S. Forest Service Southern Research Station, reaches his steady hand into the water to unearth a kidneyshell mussel, pointing to the end of the shell that shines a bright silver hue from years of erosion. He counts the lines along the shell that branches out from the eroded end. 

“This is the oldest part of the shell — they grow out like a tree,” Haag said. “This one’s probably 12 to 15 years old.” 

The 57-year-old researcher has been fascinated with mussels since he discovered them growing up in the Red River Gorge and started studying them in the 1980s when he was an Eastern Kentucky University student. They had a range of quirky names he recalls easily — the wartyback known for knobs on its shell, or the creek heelsplitter whose sharp shell edge can cut the feet of people walking barefoot in the water. 

But for Haag, he calls all of them the “gems” of a river: they filter water by feeding on algae and other microscopic organisms through their gills, provide refuge and food for other creatures and can generally reflect the health of a river’s ecosystem. 

“A lot of people just don’t know that they’re here at all,” he said. “A lot of people don’t know there are shells or clams in Kentucky. They think they’re some kind of exotic thing you go to the beach to find.” 

But just as he’s seen the diversity of these creatures, he’s also seen their startling decline, sometimes inexplicably, in waterways throughout the Midwest and South, including Kentucky. Some waterways have seen mass die-offs of these mussels or have seen populations decline in recent decades. Unique mussel species found in some tributaries, including in Kentucky, have since disappeared as more species become federally listed as threatened or endangered.

Haag co-authored a report that found the diversity of mussel species declined in Kentucky rivers, some places dramatically. Compared to historical levels to what it is now in the 21st century, the Red River in southeast Kentucky has seen an 82% decline in species diversity, from 28 to 5 species. The watershed of the Little Sandy River has seen a 39% decline in species diversity. 

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“It just makes me sad,” Haag said, mentioning he was often bitter when he was younger. “I try to focus on my opportunities to make it better.” 

An overview of the Licking River on a September afternoon.
 Researchers a part of Haag’s team wade in the Licking River on a September afternoon (Kentucky Lantern photo by Liam Niemeyer).

Recent research being conducted by Haag and others hopes to provide better evidence for why mussels seem to still be thriving in a place like the Licking River but disappearing in other waterways. 

A three-year project is studying waterways in 13 states from Wisconsin to Alabama, collaborating with wildlife management officials in these states including the Kentucky Department of Fish and Wildlife Resources. It’s being led by the U.S. Forest Service and the nonprofit conservation group American Rivers with funding coming from multiple sources including the Band Foundation, Merck Family Fund and the Tennessee Valley Authority. 

Some causes of mussel decline are well known. When dams were erected throughout the state into the 20th century, Haag said, mussel populations declined precipitously in these rivers. The flow of fish was altered or blocked by dams; mussels use fish as hosts as they grow as larvae in their gills.  Haag said when the Wolf Creek Dam was built on the Cumberland River, it “destroyed” the mussel population and diversity. 

But in some waterways, the reasons for the mussel’s decline isn’t clear. That’s why Haag and other researchers are testing theories — invasive species, water pollution, increased erosion and sediment into waterways — in hopes of providing a better grasp of how to preserve the creatures.

He said people often float ideas for mussels’ disappearance, whether it’s because of runoff from coal mining or agriculture. But those ideas don’t satisfy Haag because of what he’s seen over the past 20 years — coinciding, often catastrophic, die-offs in various places and environments. 

“It just doesn’t make sense. It’s like 10 meteors all crashing in the same spot — it just doesn’t happen,” Haag said. “That could be what’s going on but, I think that there’s probably a bigger thing happening across a large area that we don’t know about. So that’s what we’re trying to get at.” 

Haag puts his finger on the sharp edge of the "heelsplitter" mussel.
 Wendell Haag points to the sharp shell edge of a “heelsplitter” mussel. (Kentucky Lantern photo by Liam Niemeyer).

Kentucky’s mussel nursery

Jugs filled with bright green algae, a mussel’s go-to food, line the laboratory space as Monte McGregor shows off what’s been the result of more than two decades of effort for him. 

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Perfecting this food so that mussels will consume it has been a large part of McGregor’s work here, who established Kentucky’s Center for Mollusk Conservation in 2002 near Frankfort. 

In a temperature-controlled room, bins of juvenile Plain Pocketbook mussels tiny as seeds line the bottom of bins where they’re fed once a day a diet of this algae and other helpful additives. Mussels also consume bacteria in the water, McGregor said, which could be harmful to humans but end up being a meal for mussels. 

“We’re down to the science now where I can tell you how much protein they’re getting, the carbs they’re getting,” McGregor said. “I haven’t changed my diet in four years. It works really good now, so I’m not going to mess with it.” 

The water in the bins become cloudy with algae that slowly disappears over the course of several hours as the juvenile mussels filter the water. And the number of mussels being raised here can be truly massive: next door to the temperature-controlled room, McGregor is able to have over a million mussel eggs in a single incubator.

Juvenile mussels, as small as seeds, are cradled in the fingers of Monte McGregor.
 Monte McGregor picks up juvenile mussels with his fingers from one of the bins where they’re growing at his lab. (Kentucky Lantern photo by Liam Niemeyer).

His lab has been a crucial role of Haag’s research project by raising juvenile mussels that then go into what are known as “silos,” concrete containers put in various rivers, that researchers can then check on to see how mussels are growing — or not growing — in various river conditions. 

Researchers are also testing water quality and how much sediment is in the water. Haag said a common theory is that increased erosion of soil caused by humans is causing more sediment to be present in waterways, potentially choking out mussels. 

 “That has been an idea that has just pervaded muscle conservation for 30 or 50 years,” Haag said. “I realized that people never really did go back and dig into the research that supported that idea. So I did that, and I found that it was kind of a house of cards — it just wasn’t there. You know, that doesn’t mean that it’s not true. It just means there’s no support for it.”

Beakers with labels, some of them bubbling, sit on a back-lit shelf inside a fridge.
 Beakers of green and brown algae sit inside a fridge at the Kentucky Center for Mollusk Conservation. (Kentucky Lantern photo by Liam Niemeyer).

Haag said out of the more than 90 waterways across multiple states they’ve studied so far, there hasn’t been a correlation between sediment and mussel health. Some streams with little fine sediment have poor mussel populations, while mussels love other streams that are a “muddy mess.”

Other factors such as water quality are being tested with the hope that studying all the various factors can create an index to help determine where mussels might still be able to thrive. 

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For some, a last ditch effort from extinction

This research is ongoing as more mussel species across the U.S. are facing the threat of extinction. In Kentucky, 29 species of mussels are currently federally listed as threatened or endangered. Across the country, 95 species are considered threatened or endangered, and McGregor is confident at least one or two more species will be listed later this year. 

But with McGregor’s ability to grow mussels at his center, he’s had the chance to save rare species. When a truck crashed in Virginia in 1998 and spilled chemicals into the Clinch River in Virginia, it killed aquatic animals for miles including the golden riffleshell — a mussel only found in the river and another nearby tributary. 

He said he met with Virginia biologists in a McDonald’s parking lot in Pikeville in 2016, where they gave him what was believed to be the remaining three living specimens of the mussel in a last ditch effort to save the species. He brought the mussels back to his center and put the larvae in a petri dish to incubate, and in a little over two weeks he had more than 1,000 juveniles he was raising. 

He went back to Virginia the next year to help biologists release 1,000 of the juveniles back in the wild. 

Yet with that success story, there are a number of other rare, endangered mussels that could be in a similar situation as the golden riffleshell because of the recent die-offs. 

“If we find one, we got a chance to be able to do something with it. That’s how rare these animals are,” McGregor said. “There’s 15 or 20 of them that — we don’t do something with them in 10 years, they’re gonna be extinct.”

One of the researchers holds up a brown-ish mussel.
 A mussel picked up from the South Fork Licking River. (Kentucky Lantern photo by Liam Niemeyer).

McGregor said the Little-wing Pearlymussel is a prime example of an endangered mussel that he’s trying to work with, found only in a few places in the world. It used to be found in Horse Lick Creek, a tributary of the Rockcastle River — but no longer. 

He said the Rockcastle River had seen conservation efforts into the 1990s to protect the waterway, but the Littlewing Pearlymussel has still declined. Other parts of the world have extraordinary diversity of different animals, and he feels a duty to protect the diversity of mussels that Kentucky is known for. 

“The world expects us to be able to manage and protect those and keep that diversity high, just like the ones over in another part of the world,” McGregor said. “We just happen to have some of the best areas.”

This story originally appeared at

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