New DNR Project Raises Freshwater Mussels in a Mobile Lab

By Joe Zimmermann, science writer with the Maryland Department of Natural Resources.

The Mobile Mussel Propagation Trailer cultivates mussels to restore populations in the Susquehanna River basin

Annapolis, MD - A new Maryland Department of Natural Resources project is aiming to raise imperiled freshwater mussels and restore them to waters of the Susquehanna River basin—all from the back of a trailer.

DNR’s Mobile Mussel Propagation Trailer began operations this October. It’s currently parked in Susquehanna State Park and is raising juvenile mussels from the Susquehanna River, where the mollusks play an important role in filtering water, just as oysters do in saltwater.

Though some other research groups have trucks or vehicles to assist in mussel research, none are this size or operate as a fully functional hatchery.

“At this point, it’s one of a kind, no one else has this,” Matt Ashton, a DNR natural resources biologist who helps run the operations in the trailer, said at the public unveiling of the hatchery during DNR Science Week in October.

Zach Taylor, DNR freshwater mussel hatchery manager, said the hatchery will play an important role in public outreach because staff can tow it to different locations and educate residents about the importance of freshwater mussels. The hatchery will also reduce travel and handling stress in returning the broodstock of mussels back to the river.

“In general, the less stress we can put on mussels the better,” Taylor said.

DNR staff custom-built the lab to fit the space. They lined the trailer (a race car hauler by design) with tanks, pipes for running water, cooling systems and tables for workspace. The tanks hold freshwater mussels—one species at a time, with yellow lampmussels for its first stock—and several dozen fish, which play a vital role in mussel propagation.

In their early life, freshwater mussel larvae, or glochidia, are parasitic and live on the gills of fish. This allows the glochidia to gather nutrients while causing little damage to the fish, and also enhances the distribution of mussels, which fall off the fish after it has carried them through the river until they reach a stage of maturity where they can survive on their own. 

In the wild, female adult mussels, which hold larvae inside their shells, lure passing fish to come close–and then release the larvae to attach to their new host.

DNR scientists are able to recreate that natural process in the hatchery. They collect mussels from the Susquehanna River, use a syringe to extract larvae from inside the gills of female mussels, and then inoculate the larvae onto the gills of fish. After about two weeks, the larvae metamorphose and fall off the fish, then are collected in mesh nets. Scientists then monitor their growth and will eventually introduce them back into the river.

The fish, currently largemouth bass and sunfish, come from aquaculture labs at North Harford High School in Pylesville, where students raise fish that were initially provided by DNR.

DNR cultivates mussels for propagation at the Joseph Manning Hatchery in Brandywine and now at the mobile site in an effort to increase the number of mussels in Maryland waters.

There are 16 species of freshwater mussels that are native to Maryland, 14 of which are facing imperilment, largely due to habitat loss or poor water quality. Six are threatened or endangered in the state, and two are federally endangered.

“Globally and on the continent, of any faunal group, mussels are the most imperiled,” Ashton said. “While a lot of media attention is given to preserving charismatic megafauna like tigers, the reality is aquatic fauna, particularly freshwater mollusks, are significantly more imperiled at this time.”

The Mobile Mussel Propagation Trailer will use this fall and coming spring as a trial run. Ashton said they hope to transform 100,000 mussels in the spring. Transformation is the term for successful metamorphosis from glochidia to functional juvenile mussel—a marker of this early stage of development, when they fall off the fish and are able to survive independently.

The trailer cost $95,541, in addition to about $52,200 for equipment and supplies. Ashton said another advantage of the mobile trailer was the speed of its construction. It took about a year to build out, while a brick-and-mortar hatchery could take three or more years.

This fall it’s located at Susquehanna State Park, then it will move to the Joseph Manning Hatchery for the winter, where it can serve as additional lab space, Taylor said.

In the spring, staff plan to return the mussel trailer to Susquehanna State Park. After that, it will support other restoration projects–or it could hit the road.

Taylor said the team is still figuring out the plans for where to take the hatchery, but it could be brought to other stream sites to raise mussels for local release. The only limitation is access to a 50-amp receptacle, suitable water and height clearance.

DNR scientists are also considering bringing the mobile hatchery to other public events. This helps the hatchery serve its other primary goal of public outreach. Freshwater mussels and their benefits to the environment and ecosystem are not well known to the public, and the hatchery could bring more awareness to the vulnerable species, Taylor said.

The hatchery is open to park visitors when staffed. Taylor said he thinks it could be especially important as an environmental education tool for children and students.

“As a kid, I can remember a couple core moments that influenced what I wanted to do in my career,” he said. “You never know when you’re going to have that impact on someone.”

By Joe Zimmermann, science writer with the Maryland Department of Natural Resources.