BRUNSWICK MARINE WARDEN DAN DEVEREAUX pulls apart a microwaved green crab at a 2014 event in Brunswick. Devereaux says predation is a threat to the clam industry, and every fishing industry.

BRUNSWICK MARINE WARDEN DAN DEVEREAUX pulls apart a microwaved green crab at a 2014 event in Brunswick. Devereaux says predation is a threat to the clam industry, and every fishing industry.


Chad Coffin, a fisherman who has spent 27 years on local mud flats, said he hates to read descriptions of how the clam fishery is threatened, when, in his experience, it’s nearly gone.

“It’s already gone. It’s not threatened, it’s already gone,” he said while at the town wharf.

For three years, Coffin has worked with scientists and researchers in the largest intertidal field research in the state, determining how to mitigate threats to the fishery’s sustainability. Similar, but smaller-scale experiments using recruitment boxes have been conducted in the St. George River, Boothbay Harbor and other locations along the coast.

According to researchers with the nonprofit organization Downeast Institute, the results are the same: Predation is conclusively the largest killer of softshell clams, spurred by warming ocean temperatures, Coffin said, not, as is commonly thought, the result of ocean acidification and over-fishing.

Coffin said Dr. Brian Beal, a professor of marine ecology with the University of Maine at Machias, has ruined his life with the research and data conducted in the Harraseeket River.

“I used to think I was an expert before I met Brian,” he said. “I was a self-proclaimed expert.”

The idea of people being “self-proclaimed” experts poses an obstacle in determining how to build and protect the fishery, Coffin said, adding there is a disconnect within the industry, and those who are ignoring the science and holding out hope things will be cyclical and return to normal.

Studies show

In 2012, clammers warned of the green crab influx and the decrease in the softshell clam population. A research project was initiated by the town of Freeport in 2012 to determine what caused a 65 percent decline in Casco Bay landings in the last decade. Experiments conducted by the Downeast Institute in the Harraseeket River is yielding data that points to warming water temperatures spurring a rise in predation that is destroying the softshell clam fishery.

Researchers continue to test the effectiveness of different methods to protect the fishery from both native and invasive predators.

“It’s so simple, but there are so many aspects to it,” Coffin said of the research and the data produced.

“Predation is the number one cause,” said Associate Director of Research at the Downeast Institute Sara Randall.

She said the warming water temperature has allowed predators, including green crabs, who are native to the Mediterranean, to proliferate and feed on young clams. Ribbon worms, native to Maine waters, are also preying on softshell clams. Clam population drop-offs were most pronounced when water temperature peaked at 63 degrees, invigorating predators that feed on clams, Randall said.

Kohl Kanwit of the Department of Marine Resources said the department agrees predation is a significant source of mortality on the softshell clam, and said the agency has followed the progression of the project over three years, and wrote letters of support to funding agencies. When asked if she has any critiques or reservations about the data collected, Kanwit said she doesn’t.

Although predation is not new, the extent of the mortality it’s causing is, Beal contends.

“The system is out of whack, with the rise in crabs and milky ribbons worms at the same time,” he said.

What confirmed the researchers’ theory that predation is the main cause of the decline were experiments with clam pounds and recruitment boxes in the river that showed clams were settling, and growing, within the protected areas. Meanwhile, core samples taken just outside of the boxes contained very few clams.

In April, Beal and Randall filled three-by-two cages with mud and 20 pounds of adult clams. When checked, within the clam pound, there were 2,100 clams per square foot, and the outside areas showed 8.5 clams per square foot, Beal and Randall said. Although more clams could have settled in the outside areas, they were not protected from predators. Results from 2014 and 2015, at different sites, show similar results.

In 2013, clammers were told they should give up because ocean acidification is causing clams to dissolve, and is the cause of the decline, Beal said. He questioned how it could be ocean acidification when five or six independent experiments as part of their research show something different.

“There’s so much data, and time after time, it points to predation,” Beal said, “even when experiments are designed against predation.”

Plots protected from predators, regardless of the pH of the mud flats, always showed growth, researchers found, suggesting clams can survive and grow in high acidic sediments.

A solution, for a town the size of Freeport, Beal said, would be to manage the 800 acres of intertidal areas it has, and allow clammers to have small-scale aquaculture ventures.

“We’re talking about adapting, and taking advantage of Mother Nature,” said Beal. “We can’t stab a knife through every green crab — it’s not possible.”

Randall said water temperatures and cold weather winters are not as cold as they used to be, and data suggests those seasons will continue to be fewer and farther between. Beal agreed, saying that what people are waiting for are winters with ice.

What to do?

Conservation closures, without a protection aspect, the researches said, allow predators to continue to wreak havoc on the population. Although closures may have aided the clam population in earlier years, Randall and Beal argued you can’t take what worked in 1960 and apply the same techniques today.

“We need to accept the ecosystem is different than it was even five and 10 years ago,” Beal said. “We can’t sit around and wait and think they will come back, and that’s what’s driving the opposing opinion.”

Randall agreed, but added change is difficult, especially those accustomed to a hunting and gathering lifestyle, who learned how to dig clams from generations of fishermen.

The data has been presented at seminars and talks such as the Fishermen’s forum. Funding for the project has come from the town, the University of Maine at Machias, Sea Pact, and the Maine Economic Improvement fund. Randall said softshell clam research funding sources are more difficult to come by as compared to lobster research, although it is the second largest fishery in the state.

Brunswick Marine Warden Dan Devereaux, who is familiar with Beal and Randall’s research, said it is good research, and agrees predation is a threat to the clam industry, and every fishing industry.

“Beal is one of the few scientists who gets out there and digs in the mud,” Devereaux said of the professor. “If he says predation is a factor, we should heed his advice.”

He said ocean acidification is also a factor in the decline of the clam population.

“The ocean is a big sponge for carbon,” Devereaux said, which changes the pH balance and temperature of the ocean, in turn causing problems for creatures that build shells.

About 100 years ago, he said, the state Legislature ceded management of intertidal areas to towns. The law implemented allows for 30 percent of the flats to be used for aquaculture, Devereaux said, but no towns in the state have done that and he is uncertain if the state is really supportive of it. It would take a lot of investment from the town to do that, he said, including the need for Army Corp of Engineers permitting, and the overall assurance they are protecting a fragile ecosystem. The state still must approve changes to laws and regulations proposed by a town, Devereaux said.

Once a harvester has been approved for a lease for an aquaculture project, he said, the designated area is essentially no longer public property, which could cause friction within the fishing community, adding clammers will likely remember the yields of certain areas as far back as when their grandfather worked the flats.

Devereaux said adaptive management measures must be considered to keep people working. The future of the fishery may see a mix of traditional digging and leased aquaculture projects.

“Softshell clam aquaculture — nobody’s nailed it yet.” he said. “It’s a finicky creature.”

Beal said he put himself through college on the end of a clam hoe.

“Could you do that now?” Randall said. “No.”

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