ME - Researchers seek changes to save clam fishery from collapse
Warming weather has kept clam predators active, and a slow response to possible solutions has led to frustrations.
The Harraseeket River recedes slowly but steadily around Chad Coffin’s metal skiff, until the boat is beached on a partly exposed mudflat. Coffin and his daughter, Bailey Pennell, are already out of the skiff, rakes in hand and rubber boots sinking deep into the gray-brown muck.
They begin to dig — but not for soft-shell clams, also known as steamers, belly clams or Ipswich clams, a prized Maine commodity that Coffin has harvested here in Freeport for decades. Instead, he and Pennell are scrounging for quahogs, or hard clams. They fetch a lower price, but the part of these flats where any soft-shells might be found is closed to harvest after a recent rain.
“This used to be all clams when I started clamming,” Coffin said. “I would have been able to dig right there, where the mud’s showing already. And now we can’t. There’s nothing there.”
This is becoming a typical struggle for some Maine clammers. Though the soft-shell fishery is typically Maine’s second-most valuable after lobster, statewide landings for the clams are near all-time lows — down from close to 40 million pounds a year in the 1970s to fewer than 10 million pounds a year for most of the past decade.
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Coffin and some researchers are confident they know the main reason: green crabs. This invasive species eats clams voraciously, and warming waters are causing the crabs’ population to explode.
“Climate change is just that piece of dynamite that’s been thrown into that room,” said Brian Beal, a professor of ecology and longtime clam researcher with the University of Maine at Machias. “That has just changed everything.”
Beal and Coffin are among the clammers, scientists and other observers who believe the problems facing the fishery are clear. But the solutions they’re calling for have been slow to gain traction at the state level.
Warming waters drive crabs’ numbers
Coffin turns over chunks of mud on the flats in Freeport with his hand rake, periodically pulling out a quahog and tossing it in a plastic bucket. Almost immediately he also finds something else — a small green crab, sluggish with cold but alive. He tosses it into the skiff. Left out of the water long enough it will die — one down, but many thousands to go.
Coffin and others acknowledge that trying to eradicate green crabs is futile. Gabriela Bradt, a fisheries specialist with the University of New Hampshire Sea Grant who focuses in part on green crabs, blames the decline of very cold winters. Sustained, freezing weather can kill green crabs in intertidal areas, helping to keep the population in check.
“Up until about 15, 20 years ago, we were still getting really long cold winters, you know — like below-zero temperatures for extended days and things like that — and we just don’t get them anymore,” Bradt said. “Now we’ve had extended periods of warm winters, and they’re not being eradicated that way. And so that means they’re eating more, they’re reproducing more for longer periods of time, and their numbers are just out of control.”
Bradt wants to see commercial-scale harvesting of green crabs, which were introduced to North America on ships from Europe in the 1800s — but acknowledges this “eat the invasives” effort may be slow to grow and would only “bring them down to hopefully a dull roar.”
Meanwhile, the average winter low temperature in coastal Maine has risen from single digits in the early 1900s to the low 20s in recent years, according to the state climatologist’s office.
This kind of increase is a boon to green crabs. In the 1950s, the Gulf of Maine saw a short, seemingly random spike in temperatures — and with it, a proliferation in green crabs that decimated the clam sector, according to a key 1955 study, which Beal shared.
“We should have known what was going to happen because it had already happened before,” Beal said. “It’s just no one paid attention.”
Losing the next generation
Sara Randall, the associate director of the Downeast Institute, has worked with Beal on myriad studies about soft-shell clams and green crabs — including more than 30 experiments in Freeport alone between 2013 and 2018.
“We found that over 99% of the clams that are settling out of the water column (into a mudflat) are dying before they reach 1 year old,” Randall said. “The 1-year-old part is important because that means they’re not reaching harvestable size.”