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Meet Bay Scientists’ New Favorite Critter: The Freshwater Mussel

mussells hatchery
As they grow into adults, mussels at Harrison Lake National Fish Hatchery in Charles City, Va. are transferred outdoors until it's time to release them. (Photo: Crixell Matthews/VPM News)

Chesapeake Bay Foundation scientist Joe Wood is quick to rave about Harrison Lake National Fish Hatchery in Charles City, Va.

“I hope that by the time you leave here today, you think of this place as really being like a critical place for environmental issues in Virginia,” Wood told a small gaggle of press last week - “because that’s the way I think of it.” 

Press were gathered to learn about work being done at the hatchery to protect and research a little critter that’s often confused for a rock: the freshwater mussel.

Wood led a workgroup of the Scientific and Technical Advisory Committee, reviewing existing research and data on mussels. He boils it down to a few points: freshwater mussels are environmentally valuable; they’re threatened by endangerment and extinction; and they need support, specifically through funding for research and restoration.

mussells
Mussels under the sand can be identified by the distinctive breathing holes, apertures, they make. One hole is for intake, the other outtake. Mair says these holes are an important indicator when they look for mussels in the wild. (Photo: Crixell Matthews/VPM News)

Identifying a Need

The STAC report found that many mussel species are endangered or threatened, and that some of the most common are now declining rapidly as well. Much of that is due to pollution and poor water buffer management - both of which can be deadly to growing mussels.

Scientists know they fill important roles, from supporting the food chain to providing habitat to filtering excess nitrogen out of the water. Nitrogen pollution comes from fertilizer runoff, sewage releases and more, and notably causes deadly algal blooms in the Chesapeake Bay. 

Wood says research suggests an adult mussel can filter up to 15 gallons of water a day, and offer denitrification on par with the famous eastern oyster. But learning specifics on those things requires further research, and Wood says there just hasn’t been enough attention on the creatures to get that work done.

“Most people recognize that [oysters] are this valuable natural resource,” Wood said. “They’ve got benefits for water quality, they’re providing habitat for other critters, and that investments in oyster restoration is money well spent.” 

mussels
Mussels raised at the hatchery. (Photo: Crixell Matthews/VPM News)

In a few years of asking around, Wood has found that even people like marine biologists don’t have the same understanding of the extremely biodiverse freshwater mussel.

But the biologists at Harrison Lake know them better than just about anybody. 

Growing Mussels

Rachel Mair of the U.S. Fish and Wildlife Service says their first mussel hatchery was set up in 2007, after it became clear that increasingly polluted rivers were killing off mussels in the Eastern U.S..

They’ve made a lot of progress in that time. Freshwater mussels have a unique life cycle, and one that’s difficult to replicate. Many species must spend their larval stage attached to the gills of a host fish - a feat that’s accomplished by female mussels producing a lure.

bluehead chub
Bluehead chub fish are possible hosts to the larval stage of mussels. (Photo: Crixell Matthews/VPM News)

“It looks exactly like a fish,” Mair said. “It’s got an eyespot, it’s silver, they twitch it so it looks like it’s moving underwater.” When a fish looking for food comes along, it’s fooled by the convincing lure - as it bites, the mussel releases its larvae. They snap onto the gills and stay put for a couple of weeks.

So, not only does the Harrison Lake team have to raise mussels and their host fish, they also have to simulate that infestation process and then care for the mussels as they go through their fragile early stages. What’s more, there are about 25 species in the bay watershed - about 80 in Virginia as a whole, each with unique needs.

The hatchery now releases as many as 50,000 mussels yearly across a wide variety of species, all grown in buckets, tanks and ponds.

“We have mussels in a carport, a pull shed - I mean, anywhere we can grow mussels, we’re growing them, because the need is there,” Mair said. But she’s sure to note that the hatchery is essentially operating at capacity - without more buildings or people to work in them, she says there’s no way they can expand the operation.

Wood says the need is clear, “yet when you look at bay cleanup efforts, there is rarely a mention.” One of the recommendations made by STAC is that lawmakers at the federal and state level invest in mussels outside of mitigation, and instead focus on reestablishing populations watershed-wide.

“Largely yes, funding does dictate the projects that we’re working on,” said Amy Maynard of the Virginia Department of Wildlife Resources. That means some funding is location-specific - like cash to restore populations after a coal ash spill in the Dan River.

woman demonstrating mussels
Amy Maynard demonstrates how mussels are raised. (Photo: Crixell Matthews/VPM News)

Mair said with more resources, the facility could not only produce more mussels for propagation, but also publish more research based on their work that would make restoration efforts more effective.

Developing Public Interest

The STAC report says public engagement should be explored as a way to bolster populations.

“Maybe we should be focusing on people’s backyard critters, because they tend to care about them,” Wood said.

That could look like education: letting people know the co-benefits that being a good river steward has for water and wildlife populations like the freshwater mussel.

Or it could be more hands on - CBF has an oyster gardening program that sets up bay-side residents with cages and baby oysters, to be released into the wild when fully grown - Wood wonders if something similar would be possible with mussels in creeks and rivers across Virginia and other states in the watershed.

The goal, though, is to increase awareness and funding. Wood says the mussel’s importance and endangerment could put it on par with iconic endangered species like elephants.

“In our own country, when you think about endangered species, and like, what's there and what's at threat right now, it's mussels, and people have no idea.”