North America is home to over 300 species of freshwater mussels, but 75 percent of them are endangered.
Not too many people know about the freshwater bivalve, said Danielle Kreeger, science director at the Partnership for the Delaware Estuary, a clean water nonprofit. It’s considered the most “imperiled” of all plants and animals in North America.
“Here in the Delaware River Basin, in the state of Delaware, there’s about a dozen native species and really you can only find two or three of those,” Kreeger said.
“Not only have we seen the species decline, and we’ve seen the ranges, or the distributions of where they exist shrink, but the numbers have declined,” Kreeger said. “A hundred years ago, 200 years ago, most of our streams had large numbers of mussels and each mussel is going to filter 10 or 15 gallons of water every day, helping to keep the water clean, so they’re like a natural water treatment plant that exists in our streams historically that we’ve lost.”
‘Every live freshwater mussel is precious’
Kreeger said freshwater mollusks have been on state and federal agencies’ radars for the past 30 years, but they are focused solely on conserving the rare species.
“What we’ve been doing is very different. What we’ve been doing is focusing on even the common species, with the philosophy that every live freshwater mussel is precious because every live freshwater mussel is filtering 10 gallons or more water every day,” said Kreeger, who is unaware of any program, anywhere, like Delaware’s.
And because freshwater mussels are not edible, they don’t have the backing of the commercial food industry to fund conservation and restoration efforts like their saltwater counterparts, clams and oysters do.
So what’s endangering the freshwater mussels? Kreeger said the answer is complicated.
“One of the main reasons is because for a freshwater mussel to reproduce, complete its lifecycle, it needs a fish. And every single mussel species has a very specific kind of fish, a size of fish and a species of fish that it will reproduce with,” Kreeger explained.
Maybe man-made dams are keeping that specific fish host from the mussels, Kreeger speculated. Pollution and water quality issues could also have something to do with their dwindling numbers, she said.
While one or all of those reasons could be contributing to their species and population decline, Shellfish Specialist Kurt Cheng is focused on restoration.
“The restoration projects that we’ve been conducting have mainly been small scale restorations, where we’re taking a small number of mussels from healthy populations and putting them into restoration sites that we think have suitable habitat, suitable water quality so that these mussels can survive and grow,” said Cheng, who also works for the Partnership for the Delaware Estuary. “Sometimes we’ll actually deploy them with an electronic tag so that we can return to them at a later date and see if they’ve still survived in those areas.”
Checking on them several times a year, Chang and his team are able to target streams where mussels are getting washed out or are dying to see if they can find out the reasons behind why the mussels aren’t thriving
Volunteer mussel survey
Cheng knows where to place the mollusks because of information gathered through the Partnership’s Freshwater Mussel Recovery Program. The nonprofit launched the program in 2007 to survey where mussels are and particularly where they are not.
“It can tell us where healthy populations exist and where they don’t, or where might be suitable locations to look at possibly establishing more mussels,” said Jeff Long, the Partnership’s watershed outreach specialist.
Long’s job is to act as the go-between connecting people to the water and mussels. He teaches volunteers how to find mussels, how to identify them, how to collect scientifically-useful data and lastly, how to upload the data so the Partnership can access it.
The Partnership receives a mix of federal, state and private funding, but like many other nonprofits, money is always tight. That’s why Kreeger said the volunteer mussel survey really is an integral part of the Freshwater Mussel Recovery Program.
“Our scientists, we only have so many hours, we have good partners that we work with to also fill in our gaps with scientific surveys, but the public programs have been so very important.”
Kreeger said she is currently working with the state of Pennsylvania on a grant to build a long-term freshwater mussel hatchery there, her Holy Grail, in her fight to raise awareness and help restore the freshwater mussels in Delaware’s rivers and streams.