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Study: Trap green crabs

Clammers say more needed to save livelihood

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Posted: Tuesday, January 21, 2014 12:03 pm | Updated: 12:16 pm, Tue Jan 21, 2014.

FREEPORT – A town-funded study has produced lots of data on the invasive green crab, but Freeport clammers say nearby fishing towns and lobstermen must chip in if the local clamming industry is to survive the menace that is devouring their livelihood.

Brian Beal, professor of marine ecology at the University of Maine at Machias, worked with local clammers to study the effects of green crab trapping, and also conducted field trials to determine the effects of green crabs on the growth of both wild and cultured soft-shell clams. Traps were baited with clams from May 27-Nov. 5 on the upper stretches of the Harraseeket River.

The crabs that were caught, which were measured and the gender determined, produced what Beal called a “wealthy data set.”

Beal, who also admitted there were problems with the study, provided the Town Council on Jan. 14 with the following conclusions:

• Green crabs are killing clams.

• Fencing or netting can work. Netting is easier to accomplish.

• The first two experiments at Little River started too late in the year. Beal tried to get the work started in April, but the U.S. Army Corps of Engineers didn’t approve the project until July. An earlier start would have yielded a much better sample of results.

• It is preferable to remove the female green crabs.

• The fences eroded at Little River probably because they were not curved enough, and couldn’t withstand the tide and winds.

 Beal said he found no relationship between “soak time,” or the time traps were in the water, and the number of crabs caught. Location, he said, was more important.

“The take-home message here is that if you want to catch green crabs, you should probably set your traps every day, instead of letting them sit out there,” he said.

In 2012, the Freeport Town Council earmarked $100,000 to study the clam flats and decide on a course of action. The project is overseen by the town’s Shellfish Commission. 

Some of the fencing used to capture green crabs was compromised by tides and wind. In the trapping method, clammers and others involved in the effort consistently hauled in cages full of the crabs – literally tons of them.

“The fact that they kept catching the same amount of crabs probably means they probably didn’t make a significant dent in the population,” Town Manager Peter Joseph said last week.

Clammers are ready, meanwhile, to keep digging. Beal will be back the next two summers with the help of a state grant.

Last Thursday, Tommy Bennett II and Jason York, both of Freeport and both members of the Maine Clammers Association, assessed the situation as they sat in their respective pickup trucks at the town dock in South Freeport.

“We need more participation,” Bennett said. “Surrounding towns need to help us find out how to get rid of this invasive species. We’ve got numbers. We’ve got data and that’s what they’re looking for. But you can’t tell by one year.”

York concurred.

“Every town in the basin needs to do it, too,” he said.

Bennett said that he and other clammers stand ready for Beal and his crew of volunteers to return this summer.

“We’ve got to do the study again this year, and the next year, until we get a learning curve,” he said. “We’ve got to. We’ve got no choice.”

Bennett said that green crabs started feeding on oysters and mussels in deeper water, and then ate their way into tidal waters, devastating the clam population.

“It’s like Custer’s Last Stand,” he said.

Beal told the Town Council last week that workers collected more than 300 hauls, at 1-10 traps per haul. They brought in 6 metric tons of green crabs, averaging 10 pounds per trap, and 11,715 crabs were measured.

“That’s a lot of work,” he said. “The sex ratio was completely skewed toward males. It was more even later in the season.”

The Spar Cove clam flats provided a resource survey, Beal said. They found only 3.2 clams per square foot, and 90 percent were too small for commercial use.

“What the survey tells us,” he said, “is we’ve lost our resource at the low- and at the mid-water mark. That’s why clammers concentrate on the high-water mark.”

Beal then told the council that maintenance of the fencing and nets was “abandoned” after he left in July. The fencing was patched, he said, but there were gaps.

“My repeated attempts to get data went unheeded,” he said. “The experiment was compromised.”

Beal added that of the 10 nets installed, four were missing, and that traps were left out of position.

Beal said he saw pieces of fencing in November near Indian Island. Maintenance of Little River fences was abandoned around the same time as those at the Recompence shore, he said.

“I call it a darn mess,” he said.

Tracy asked why the project manager wasn’t better informed.

“I don’t know why this happened,” Beal said.

Bennett, who was not at the meeting, said he does know what happened.

“The fencing was not properly installed,” he said. “The screws were put in with no washers, so the flashing ripped off. I could tell that when the tide was ripping out, it was going to peel that flashing right up.”

Conferring with the Maine Clammers Association, Beal said, he set up another experiment in August, to study the flats at Little River and Recompence. They placed some clams in plant pots protected with netting, and others in pots with no protection, at Recompence flats. Some crabs were able to get their claws through the holes in the bottom of the pots, but 60 percent of the clams survived, he said. No clams were found in the pots left unprotected.

“That’s an important result,” Beal said. “If you do nothing, you will have no clams.”

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