Midcoast researchers prepare for new battle with invasive green crabs

Brunswick Marine Resources Officer Dan Devereaux checks a trap designed to catch invasive green crabs in Buttermilk Cove on Friday morning. The traps are part of a study designed to figure out the best way to defend valuable clams from the voracious crustaceans.
Troy R. Bennett | BDN
Brunswick Marine Resources Officer Dan Devereaux checks a trap designed to catch invasive green crabs in Buttermilk Cove on Friday morning. The traps are part of a study designed to figure out the best way to defend valuable clams from the voracious crustaceans. Buy Photo
Posted July 02, 2014, at 3:39 p.m.
Brunswick Marine Resources Officer Dan Devereaux stands aboard an airboat after checking a trap designed to catch invasive green crabs in Buttermilk Cove on Friday morning.
Troy R. Bennett | BDN
Brunswick Marine Resources Officer Dan Devereaux stands aboard an airboat after checking a trap designed to catch invasive green crabs in Buttermilk Cove on Friday morning. Buy Photo
A trap designed to catch invasive green crabs sits in the mud in Brunswick's Buttermilk Cove on Friday morning. The traps, scattered throughout the mudflat, are part of a study designed to figure out the best way to defend valuable clams from the voracious crustaceans.
A trap designed to catch invasive green crabs sits in the mud in Brunswick's Buttermilk Cove on Friday morning. The traps, scattered throughout the mudflat, are part of a study designed to figure out the best way to defend valuable clams from the voracious crustaceans. Buy Photo
Brunswick Marine Resources Officer Dan Devereaux checks a trap designed to catch invasive green crabs in Buttermilk Cove on Friday morning.
Troy R. Bennett | BDN
Brunswick Marine Resources Officer Dan Devereaux checks a trap designed to catch invasive green crabs in Buttermilk Cove on Friday morning. Buy Photo
Brunswick Marine Resources Officer Dan Devereaux steers an airboat after checking a trap designed to catch invasive green crabs in Buttermilk Cove on Friday morning. The traps are part of a study designed to figure out the best way to defend valuable clams from the voracious crustaceans.
Troy R. Bennett | BDN
Brunswick Marine Resources Officer Dan Devereaux steers an airboat after checking a trap designed to catch invasive green crabs in Buttermilk Cove on Friday morning. The traps are part of a study designed to figure out the best way to defend valuable clams from the voracious crustaceans. Buy Photo
Brunswick Marine Resources Officer Dan Devereaux steers an airboat after checking a trap designed to catch invasive green crabs in Buttermilk Cove on Friday morning. The traps are part of a study designed to figure out the best way to defend valuable clams from the voracious crustaceans.
Troy R. Bennett | BDN
Brunswick Marine Resources Officer Dan Devereaux steers an airboat after checking a trap designed to catch invasive green crabs in Buttermilk Cove on Friday morning. The traps are part of a study designed to figure out the best way to defend valuable clams from the voracious crustaceans. Buy Photo

FREEPORT, Maine — This time last year, Brunswick Marine Resources Officer Dan Devereaux pulled back a clump of mud along the banks of Harpswell Cove and revealed a swarm of green crabs frenetically scurrying for cover.

But when Devereaux dug a clam rake into the mud in Buttermilk Cove on Friday, he found only a few scattered mussels. Nearby, a cylindrical trap that last summer was teeming with the invasive crustaceans now holds only a single, native crab.

So far this season, the European green crabs that for the last couple of years decimated lucrative clam flats in Casco Bay have not appeared.

Researchers aren’t sure why — one theory is that unseasonably cold water has kept the crabs at bay — but they are trying to find out, while hoping that the crab infestation wasn’t just delayed this year by the length of time it took for coastal waters to warm.

A number of studies in the midcoast region are focused on learning how best to enhance the clam population and protect it from predators, most notably the invasive green crab.

Brian Beal, a researcher from the University of Maine at Machias and the nonprofit Downeast Institute for Applied Marine Research and Education, is leading six separate studies in Freeport, funded by more than $550,000 in grants from the the Saltonstall-Kennedy program of the National Oceanic and Atmospheric Administration and National Marine Fisheries Service, the University of Maine Systems and Sea Pact, a sustainable seafood alliance

In an “upweller,” or incubator, on the dock outside Harraseeket Lunch and Lobster in South Freeport, 1 million seed, or baby, clams will grow until harvesters plant them next spring.

In Collin’s Cove and Wolfe’s Neck in the Harraseeket River, juvenile clams are protected by netting in plots, and in Staples Cove, mesh predator exclusion fencing surrounds 30-foot square plots of clams.

Crabs caught in traps scattered throughout the upper and lower Harraseeket River will allow researchers to study trends in crab populations.

“What we know is that last year at this time, we were averaging about 10 pounds of green crabs every time those traps were hauled, and we were hauling three times a week,” Beal said. “This year, less than a pound per trap is being hauled. Whether that trend continues during the summer — we all hope that it does, of course — remains to be seen. Every week that goes by, we’re learning that much more. But I don’t dare to make any predictions about whether green crabs are going to come back in full force.”

Until the town of Freeport last year provided $165,000 in funding to research green crabs and softshell clams, no one had really studied the problem, according to Beal.

“It’s unfortunate, but here we are,” he said.

Other projects, funded by the state and the New Meadows River Partnership, are underway elsewhere in the southern midcoast. The town of Harpswell closed nearly 15 acres at the mouth of Strawberry Creek this year to allow researchers to study the most effective method of removing the crabs. West Bath is conducting a similar project.

Beal said he has heard lobstermen are finding green crabs in deeper waters, which he acknowledged could be a concern for the lobster industry. While previous studies examining the diet of green crabs did not find lobster parts, the current studies are examining the diets of green crabs to see if juvenile lobsters are being consumed by the predators.

In Brunswick, where the softshell clam inventory is down about 40 percent, Devereaux said, “We’re anxiously waiting … the fencing is installed, the traps have been put down. Now we just wait for the crabs to crawl.”

It may not be long.

On Tuesday, Sara Randall of the Downeast Institute pulled a few traps in the Harraseeket and saw 30 of the small creatures scurrying over each other.

“I’m thinking the crabs might be coming,” she said.

 

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