Maryland Department of Natural Resources biologists retrieved 358 of 368 juvenile eastern elliptio mussels from protective concrete silos in the Potomac River this fall, posting a 97 percent survival rate in the first field phase of a pilot restoration project.
The year-old mussels, each smaller than a fingernail, spent the summer inside 25-pound concrete bowls anchored along a stretch of the upper Potomac near Indian Head and upstream of Dam No. 5 west of Hagerstown. The silos allowed the bivalves to feed on natural river particles while shielding them from predators and current.
“It’s rock solid,” said Matt Ashton, DNR shellfish and freshwater mussel program manager. “We can say across the entire area we studied, there was nothing affecting survival this summer.”
After measuring growth, the team hand-placed the mussels directly into the riverbed sediment, where they will overwinter without protection for the first time. Scientists marked shells with colored glitter and attached radio tags to one in 10 juveniles to track survival and movement next year.
The pilot is informing Maryland’s forthcoming comprehensive freshwater mussel restoration plan for the upper Potomac, one of 10 tributaries targeted under the updated Chesapeake Bay Watershed Agreement expected to be adopted this month. The agreement commits Bay states to implement key restoration recommendations in at least five tributaries by 2040.
Freshwater mussels, North America’s most imperiled animal group, filter algae, nutrients and sediment while serving as food and habitat for fish, otters and macroinvertebrates. A single adult mussel can filter up to 15 gallons of water per day.
DNR Secretary Josh Kurtz called the effort the beginning of an exciting era for mussel recovery in Maryland, where 14 of 16 native species are considered rare, threatened or endangered.
Separate funding will soon boost production capacity. A $23 million commitment from Constellation Energy, tied to the October 2025 Water Quality Certification for Conowingo Dam, will support construction and operation of a dedicated mussel hatchery at the Joseph Manning Hatchery complex in Brandywine. Construction is scheduled to begin in 2028.
The existing hatchery, managed by Anna Dellapenta since April, produced nearly 75,000 juvenile mussels this year — almost ten times the 2024 output — using techniques refined at Virginia Tech and fish hosts raised on-site.
The Potomac pilot received $273,682 from the National Fish and Wildlife Foundation’s Central Appalachia Habitat Stewardship Program, leveraged by a $185,000 Maryland Senate appropriation.
Ashton noted that historical dam construction, pollution and habitat loss have prevented natural recolonization even in now-clean sections of river. Data from the pilot indicate the upper Potomac could support millions more mussels if populations are re-established.
