Restoring Freshwater Mussels to Maryland Streams

The presence of freshwater mussels indicates a healthy stream, with the bivalves acting as natural filters – removing excess nutrients and sediment from the water and then slowly releasing food for other aquatic life. However, the once-plentiful mussels have been on a decline in Maryland streams due to a number of factors.

To help restore the state’s mussel population, Maryland Department of Natural Resources biologist Matt Ashton and Chesapeake Conservation Corps member Jennifer Tam are working to produce and rear freshwater mussels, with assistance of the Joseph Manning Hatchery in Brandywine.

“Our hatcheries have extensive experience in fish production for recreation and restoration purposes, but mussel culture requires the development of entirely new techniques,” said Brian Richardson, the department’s program director of fish health and hatcheries. “We look forward to applying this newly acquired knowledge to support reintroduction of these valuable mussel species to historical habitats throughout Maryland.”

More than 300 species of freshwater mussels exist in the United States and 17 of those can be found in Maryland, including one federally endangered species and three state-endangered species.

The restoration team has spent the past few years studying how two commonly occurring freshwater mussel species, the Eastern Elliptio and Alewife Floater, fare in captivity before they proceed to investigate how they would survive in the wild.

Unlike oysters, freshwater mussels have a complex reproductive cycle. Their larvae must temporarily attach to a fish before they mature into a juvenile mussel. Some mussels can use many different fish species as a host, while other are restricted to just a few. Many of the mussels in Maryland use migratory fish as hosts.

“By working first with common species, we can evaluate what strategies provide us the best chance for a successful restoration outcome without requiring a large investment of resources or time,” Tam said.

The team’s experience will contribute to the goal of establishing a culture facility for freshwater mussels, and begin experimenting with releases of cultured mussels to restore their populations and ecosystem function as filter feeders.

“While it may sound unusual, we are applying tools have been used in other states to conserve mussels for years,” Ashton said.

The project is paid for, in part, by federal funds administered through the department’s Wildlife and Heritage Service.