Is there ‘green’ to be found in invasive green crabs?

Posted Dec. 18, 2013, at 5:41 a.m.
Last modified Dec. 18, 2013, at 2 p.m.
Green crabs caught by volunteers in Northern Bay fill a dinghy in this June 2012 photo. According to Bailey Bowden, chairman of the town's shellfish conservation committee, the crabs in the boat were caught in a 12-hour period with 10 lobster traps. Bowden was among several hundred people who participated Monday in a University of Maine conference about what should be done to control the crabs' booming population in Maine.
Pat Wardwell photo
Green crabs caught by volunteers in Northern Bay fill a dinghy in this June 2012 photo. According to Bailey Bowden, chairman of the town's shellfish conservation committee, the crabs in the boat were caught in a 12-hour period with 10 lobster traps. Bowden was among several hundred people who participated Monday in a University of Maine conference about what should be done to control the crabs' booming population in Maine.

ORONO, Maine — Fishermen, regulators and scientists are trying to determine if the booming population of invasive green crabs along Maine’s coast might turn out to be green in more ways than one.

The “explosion” of green crabs in Maine is the latest example of shifting territory for marine species in the Gulf of Maine, which scientists have said can be linked to recently warming ocean temperatures. The crabs have been blamed for the decimation of eelgrass beds, damage to mud banks in salt marshes and plummeting numbers of softshell clams along the shore in the past two years.

Several hundred people gathered Monday for a conference at the University of Maine — some in person and some online — to talk to each other about green crabs, to see what might be done to reduce their numbers. If a way can be found to create a market for the menace, it could do a lot to provide incentives for people to go out and catch every last green crab they can find, before the softshell clams disappear and the marsh banks collapse into the sea. But finding a way to make money by selling the crabs has been elusive.

Patrick Keliher, commissioner of the Maine Department of Marine Resources, said he has seen firsthand the damage the crabs can cause to the shoreline.

“What we are finding is that it is happening everywhere,” he said of the scope of the infestation along the entire coast. “At the end of the day, we need to find a way to eradicate these critters to the best of our ability.”

Scientists at the conference said that green crab populations also have skyrocketed in the maritime provinces in Canada. The crabs traveled across the Atlantic in ships and have been in North America since the 1800s, but it is only in the past couple of years that their numbers have surged, they said. Warmer temperatures in the Gulf of Maine, a lack of predators and competitors in their habitat, and the absence in North America of a parasite that inhibits their reproduction rates in Europe all are considered factors in their population surge.

Fishermen and others at the conference told attendees about the severity of the problem. Officials in and around Brunswick and Freeport have been among the first to try to do something about it, due to the prevalence of the crabs in Maquoit Bay, where softshell clams have been hit hard by the proliferating crustaceans.

Dan Devereaux, resource officer for the town of Brunswick, said there are areas around the edge of the bay where the crabs have burrowed extensively into the mud banks, causing large sections to tumble down into the water. A video he posted on YouTube shows the crabs skittering about as a fisherman unearths their burrows. Warning: Video contains coarse language.

“We’re losing coastline in Brunswick at a rapid rate,” Devereaux said.

Bailey Bowden, chairman of the shellfish conservation committee in the town of Penobscot, said that green crabs have wiped out softshell clams in Northern Bay, part of the Bagaduce River estuary that branches off the eastern side of Penobscot Bay. He said that the bay has produced more than 50,000 pounds of softshell clams in some years. But in 2012, after green crabs started showing up in the bay, the local population of clams dropped to nothing. Fishermen still can find some softshell clams there, he said, but not enough to make a living.

“You can’t even eat on that [amount]” he said of the softshell clams that remain.

Bowden added that in June 2012, he and a few other people made an effort to catch crabs in Northern Bay, just to see how many they could remove from the estuary. With 10 lobster traps, he said, they caught enough in 12 hours to fill a rowboat.

“We realized we had an invasion of green crabs,” he said. “We think green crabs will eat anything that can’t get away from them.”

There have been other volunteer efforts along the coast to catch the crabs — DMR requires people who deliberately harvest any type of crab in Maine to have a license — but those efforts have proven hard to sustain, given the extent of the problem and the amount of effort required, officials said.

Part of Monday’s conference touched upon potential markets for the crabs, but no one could offer any proven way to sell large amounts of them for enough money to make catching crabs worthwhile. The crabs can be used as compost but they don’t fetch enough money for compost companies to pay for them, officials said. Compost firms generally accept them as a free waste product.

Large green crabs can be processed for meat like Jonah crabs, but the idea is to catch all the crabs, not just the big ones, and most of them are too small to pick for a profit. The meat from green crabs has good nutritional value but attempts to find ways to process and market them, either for their chitin — a compound in their shell that has industrial applications — or for large-scale human consumption, have so far been unsuccessful.

“We don’t have a market yet, but we are certainly trying,” said John der Kinderen of WNWN LLC, an Arundel-based waste technology firm.

Keliher said that, despite the lack of obvious solutions at Monday’s conference, fishermen, regulators and businessmen should continue to work together to search for ways to address the problem. Mother Nature could possibly string a few cold-water winters together in the gulf, which likely would put a dent in the green crabs’ numbers, he said, but people shouldn’t wait for that to happen.

“We can’t bet on that,” Keliher said. “Cold weather and capitalism will drive solutions.”

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