Philly’s lab-grown mussels are crucial to cleaning rivers. Local scientists just made a major breakthrough.

What if there was a way to clean Philadelphia’s rivers using freshwater mussels? No, not the saltwater kind served up at the local seafood shack. These small clam-like creatures lay on the floor of rivers and eat chemicals, bacteria, and other debris in waterways.

The Fairmount Water Works has been exploring this possibility for five years. A cohort of six agencies, including scientists from the Fairmount Water Works, has been researching methods to improve biodiversity, clean waterways, and give many aquatic creatures a fighting chance against pollution.

In the Water Work’s mussel hatchery, just one of its many initiatives, senior scientist Lance Butler and program specialist Shannon Boyle are leading efforts to lab-produce freshwater mussels, particularly “alewife floaters,” to improve the quality of Philly rivers. They recently made a groundbreaking discovery, one that’s not been seen before anywhere in the world, Butler said.

Instead of attaching mussels to native fish like alewife, shad, or river herring for mussel production, Butler and Boyle have introduced mussels to a recreational sporting fish that is both cheaper and easier to source — the hybrid striped bass.

The heartiness of the hybrid striped bass in lab environments resulted in more than doubling of mussel production, from 80 mussels per fish to over 200.

This breakthrough comes at an opportune time. The 600-square-foot hatchery, which produces between 20,000 and 40,000 mussels annually, will soon relocate to a facility in Bartram’s Garden. This move will enable the production of up to half a million mussels per year, according to Butler, who has worked as a city watershed scientist for 25 years.

“Our goal is to get a million mussels back into the river,” said Boyle. “That will be our first step in making a dent in our water restoration efforts.”

Mussels are bivalve mollusks, similar to clams and oysters, with hinging shells. They live mostly sedentary lives along the floors of waterways, consuming various particles and chemicals, essentially cleaning the water.

One mussel can filter up to 15 gallons of water per day, according to the Massachusetts Division of Fisheries and Wildlife. Oysters can filter 20 to 30 gallons of water per day but don’t grow as densely as mussels.

A century ago, these mussels lived in abundance along hundreds of miles of the Schuylkill, according to surveys in 1909 and 1919 by Arnold Edward Ortmann, a Prussian-born zoologist . Today, of the more than 300 species of mussels in the U.S., the majority are either threatened, endangered, or extinct, Butler said.

“The major contributing factors that have led to mussels’ demise are the construction of dams and other impediments that reduce the number of fish that mussels can attach themselves to — fishes are basically a mussel’s Uber,” Butler said. “The other factor is unregulated pollution. But, since the Clean Water Act and improvements in water treatment facilities, water quality has improved substantially where we can actually reestablish these freshwater mussel beds.”

For decades, scientists across the U.S. have looked to shellfish, like mussels, oysters, and clams, to clean waterways, including the Bronx River in New York, the Chesapeake Bay, and the Gulf Coast.

The Fairmount Water Works began its efforts in 2018. Boyle and Butler recently tested whether mussels could survive in the slow-moving, poor-quality water of the Manayunk Canal.

“Originally, we thought that we weren’t going to see any good growth rates and that we’d probably have some die off — we just didn’t really have optimistic outlook,” Boyle said. “What we found in comparison to our reference site, a much clearer spot of the Schuylkill River, is that these mussels love it there. They’re growing faster, they are healthy — their growth rate is insane. We have a lot of hope for this project.”