Just past sunrise on a warm August morning, Northeastern University marine science professor David Kimbro stood ankle-deep in the waters of Plum Island Sound.
He carried what resembled a stack of white pizza boxes — only they were made of PVC and had black mesh on top. Once the tide dropped, Kimbro and his team rushed to swap the boxes for others that had been sitting in the mud for a month.
In total, the scientists hauled in 45 mud-filled boxes that morning and motored them back to the research station nearby on Massachusetts' North Shore. Inside, they hoped to find a bevy of soft-shell clams.
This scrappy, muddy work was part of a two-year collaborative effort by ecologists to understand the problems facing soft-shell clam diggers on Massachusetts' North Shore.
The number of soft-shell clams commercially harvested in New England has steadily declined over the last century, according to NOAA Fisheries data. In 1950, clammers harvested 8.9 million pounds of soft-shell clams, averaging about 5 million pounds per year until the 1980s. By 2024, however, the harvest was only 1.75 million pounds, indicating a nearly 80% decline.
Couple this with closure days triggered by runoff and sewage spills, and it makes it hard for shellfishers to earn a livable income.
Patrick Saunders' family has been digging clams in Rowley for at least six generations. Saunders used to clam commercially. But once he had three young children, he did a reality check.
"It's just not possible to support a family," Saunders said.
In 2024, scientists with the Plum Island Ecosystems long-term ecological research program invited shellfishers, like Saunders to meet at the back bar of an iconic local seafood joint, Woodman's of Essex.
"They sent out emails, flyers, everything they could think of," he said. "Clammers aren't exactly notorious on social media."
The scientists, who are associated with the Marine Biological Laboratory-run research station in Rowley, had a couple of questions for their mudflat neighbors: "What concerns you about clamming these days?" And how might their scientific tools help?
One of the biggest complaints shellfishers had: Something has been eating the soft-shell clams.
Clammers pointed to the green crab, an invasive species plaguing New England waters since the late 1800s. But no study has yet confirmed or understood the impact of green crabs in this particular location — the marshes and waters of Plum Island Sound.
That's where David Kimbro and his band of scientists hope to be of service: By putting out these boxes, they aspire to find conclusive evidence of what's going on.
"We're all hemming and hawing and saying it's this or it's that. But you can't come up with a solution that's going to work unless you know it's exactly happening because of X, Y and Z," Kimbro said.
Outsmarting a predator
Further north, at the Downeast Institute in Maine, marine ecologist Brian Beal has been studying the effect of green crabs on Maine's soft-shell clams since the 1980s.
"They smash things and they just … crunch. There's nothing left of the clam after a green crab is done with it," Beal said.
Beal created the original protective boxes that inspired those on Plum Island as a way to understand the tiniest part of a soft-shell clam's life cycle. Technically called recruitment boxes, they also go by the moniker "Beal boxes."
Clams spend their first few weeks of life floating around as plankton. But they quickly grow heavier and sink to the bottom, where they grow a shell and take on their trademark clam shape.
But green crabs also eventually settle in the mud alongside their prey. That's why Beal's boxes are lined with a mesh that's only big enough to let baby bivalves — the soft-shell clams — fall through.
Beal said there's a "stark" difference in the number of clams he'll find in the boxes versus unprotected on the mudflats. In a core sample of mud without protection he might find two or three clams per square foot. But in a recruitment box, he's found up to 450 clams per square foot.
"There's clams settling to the mudflat, but there's not enough to swamp out the effects of predators," Beal said.
In other words, the clams are still reproducing — but not in large enough numbers to withstand the amount eaten by hungry predators.
In recent years, there's been a push to trap adult green crabs for human consumption as a way to control the population and mitigate their negative impacts. But Beal is skeptical.
"You couldn't eat enough green crabs to make a dent in what they do ecologically," he said.
"There's only one thing that can take care of green crabs, and ... it isn't you and me," Beal said. "It's the weather."
As the average winter surface water temperature rises, so do the number of green crabs in the following years. But in winters where temperatures drop and the ocean freezes, green crab numbers actually decline.
New England ocean temperatures are on the rise as a result of climate change. In Casco Bay, where Beal does most of his research, the average water temperature has steadily increased since the mid-1990s. It's a boon for green crabs. And more pressure on the shellfish industry.
The reveal
Back in Rowley, David Kimbro's group pried off the staples holding the boxes together and pulled back the mesh, peering inside.
At first, it just looked like mud. But then the mud moved. It was full of life: amphipods, worms and clams. There were the pearly, oval-shaped soft-shell clams and the thin, gray tubes of razor clams.
All the clam species will be measured and counted back at the lab to understand where and when soft-shell clam larvae are settling. They'll compare their findings to unprotected samples from the mudflats.
"And if there's clams in our boxes, that shows us that there are larvae out there and that they are dying, but our boxes are protecting them from that," said Grace Abe, a master's student at Northeastern University working with Kimbro on this research.
It's just one data point to better understand where, when and how these important clams grow in the ancient marsh. And for shellfishers like Patrick Saunders, he hopes this collaboration between the industry and scientists will mean that one day it will be easier to make a living off the land again.
"I don't want to get, like, woo-woo," Saunders said. "But I hope that my kids can go out and eat from the same shellfish beds that my great-grandfather did."
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