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Maine Clam Farming Experiment Aims to Protect Resource from Green Crab Invasion

GEORGETOWN, Maine - For generations, Mainers have harvested clams by digging down into the tidal flats along the coast, moving from spot to spot and carefully pulling them out one by one from the muck. But the clam, and the clamming industry, are facing a new challenge, with the huge increase in recent years of the invasive predator known as the green crab.
One harvester in the Midcoast has employed an unusual method to protect his resource from green crabs, and it's an approach that could one day be adopted statewide.

If you're going out onto the mud flats at low tide, you're obviously going to need stout rubber boots. But you'll also need to know how to walk in them

"Always toes first, never put a heel in the mud," says Chris Warner. "Touch your toe down and go. Don't let it suck down in - once the suction starts, it's over."

On a recent sun-drenched afternoon, Warner offers a tour of the Heal Eddy restoration project: a 2.3-acre soft-shell clam farm he runs in the small community of Georgetown, near Bath. It's the first commercial-scale clam farm in the state, he explains, and it's built to guard against one predator above all. "It's to beat the green crab problem, is what it's designed to do."

Warner has been clamming for more than 25 years. He got an up close view of the explosion in European green crab numbers about three or four years ago, as they munched their way across thousands of acres of Maine clam flats, feeding on bi-valves. Juvenile soft-shell clams are a particular favorite.

Credit Courtesy Maine.gov
The voracious green crab, and worries that it could decimate the state's clamming industry, prompted the experimental clam farming project.

The crab incursion has been tempered by a couple of harsh winters. But Warner says they're still very much in evidence, as he points to a crater-shaped depression in the mud - made by a green crab.  "Yeah, he burrowed down in - he saw a clam or he wanted to get out of the sun."

To protect against the crabs, Warner has planted beds of clam seeds - which he buys from a local hatchery - under protective nets. More than 90 netted plots cover the flats. Each net occupies about 200 square feet at high tide and protects up to 5,000 clams growing underneath.

"The nets are dug on the perimeters all the way around," Warner says. "We've dug them down about 8 inches, so there's a barrier under the net as well.  So worms, crabs - it blocks pretty much all predators."

"Do you have any indication so far of have successful it's been?" I ask.

"Well, when we look under the nets it's extremely successful," Warner says, "and you'll see in a minute when we walk around that area between the nets where there hasn't been any seed put and no effort's done, there's virtually nothing."

To confirm the effectiveness of the nets, Warner planted five plots with clam seed but without netting. The result? "It was a buffet for the crabs," he says.

"What we're trying to do here, all of us in the state in fisheries, is trying to figure out how to deal with the climate change problem," says John Hagan. Hagan is with the non-profit Manomet Center for Conservation Sciences in nearby Brunswick. He has been involved in the project since it was launched in May of last year.

"The water is warming, the green crabs are coming on, and everybody is really trying to figure out how to adapt to the changing ecosystem," Hagan says. "So Chris and I have one idea about how to adapt to that. We think it's going to work. Science will prove whether it does or it doesn't."

Hagan says that question will be answered at the end of next summer when the clams reach harvestable size. If successful, the initial investment of $9,000 will reap  projected revenues of up to $60,000 every two or three years.

The federal government seems to have confidence in the project, says Hagan. He says Manomet is expecting a grant from the National Oceanic and Atmospheric Administration for nearly $300,000 to develop the net-farming concept in other Maine communities.

The aquaculture industry is also excited by the prospect of boosting the state's $19 million soft-shell clam industry.

"I think it's enormously significant," says Sebastian Belle, the executive director of the Maine Aquaculture Association. "If you think about the tens of thousands of acres of inter-tidal zone that are currently under-utilized, we could, in very short order, take existing clam landings in the state and increase them by a hundred-fold. That's an amazing opportunity for the state."

Not everyone's a fan of clam farming. Some local diggers have spoken out against the Heal Eddy project , arguing that it could threaten their livelihoods, put a public resource into private hands, and lead to large-scale commercial farming operations.

Sebastian Belle says these fears are over-stated: There are legal protections in the place at the state level, he says, that would prevent a private entity from occupying too much of a community's inter-tidal zone.

And, in the case of Heal Eddy in Georgetown, supporters point out that the project only occupies a small, fairly unproductive area.