This article was originally published in The Times Record on October 15, 2014 and was written by Rosanna Gargiulo. View the original article here.
As the invasive green crab continues to influence the trajectory of the local clamming industry, early results from a study in Georgetown indicate that seeding clams in late fall — after crab activity has ceased — may prove beneficial to the vulnerable juvenile clams.
Three green crab traps are set biweekly at the site of the Heal Eddy Restoration Project, a 2.3-acre conservation closure at the mouth of the Sheepscot River. Harvester Chris Warner planted a 70-plot demonstration clam farm at the site with support from the nonprofit sustainability organization Manomet and Georgetown Shellfish Committee member Jay Holt.
The traps allow Manomet president John Hagan, working with Ruth Indrick of the Kennebec Estuary Land Trust and volunteer Kate MacKay, to measure the size of the green crab population. Manomet records the size and sex of each trapped crab to monitor seasonal changes. Probes near the trapping sites record temperatures at 30- minute intervals.
On a recent Sunday morning, the group counted the number of crabs trapped in a 24-hour period to answer what Hagan called a very simple question: “At what temperature do the green crabs go away?”
A total of 289 green crabs were caught between 9 a.m. on Oct. 11 and 8 a.m. Oct. 12, said Hagan, most of which ranged from 30 to 60 millimeters across the broadest part of the shell. The sex ratio of crabs has changed, he said, with a larger number of females in this sampling than previously trapped.
“This is the only site I’ve trapped, so I don’t know how it stands as a comparison, but it seems like a lot to me,” said Hagan. “Two weeks ago, we caught about this many — and those were disposed of — so it’s like they keep proliferating.”
JOHN HAGAN, president of Manomet, trapped, measured and recorded the sex of green crabs with Ruth Indrick of KELT and volunteer Kate MacKay. The group will continue trapping biweekly until the falling temperatures deter green crab activity. KELT received a grant from the Maine Outdoor Heritage Fund last spring to focus on green crabs, said Indrick. Since then, the organization has partnered with groups in several municipalities to determine through trapping efforts how pervasive the green crab is in the Kennebec estuary region.
“It does seem to really vary from bay to bay and from site to site,” said Indrick. “At one site in Arrowsic last spring there was a pile of green crabs and they were mostly female, then at another site there were maybe half that number and more of them were male.
“Some sites have larger crabs than other sites, and some sites have hardly any crabs at all,” added Indrick. “We don’t really know why it varies, or where they go in the winter, but there is some anecdotal evidence that some of the larger crabs go out to sea when it gets cold and smaller ones hide up in the banks.”
Nearly all sites report decreased numbers of crabs this year compared to last year, but Indrick said it is too soon to tell if a dwindling population trend will continue.
“Right now we’re just trying to establish a baseline, but population trends seem to correlate with winters,” said Indrick. “In the ’50s there were a series of warmer winters and the (green crab) population got really high, and then with a series of severe winters in the ’60s populations really dropped a lot.
“After last winter, it seems like some of the younger year classes of green crabs might have been killed, but some of the older ones are still there,” she said. “In a year or two the population could rebound because it’s only a year or two worth of green crabs that may have been killed.”
The current trapping study was spurred by the discovery of a small number of green crabs inside intact netting used to cover the majority of the clam beds at Heal Eddy to protect the seed clams from predation.
“Walking around the nets, you don’t see anywhere where they would get in,” said Warner, as he surveyed the site. “The (crabs) we’ve seen in the nets have all been dead — it looks like they came out to molt and then were too fragile to burrow back down before the sun hit them.”
The crabs have not visibly damaged the clam plots, said Warner, but it is unknown how deep green crabs are able to burrow in the flats, if they have the ability to move laterally under the nets, or if they were settled deep in the flats between tides when the plots were planted.
“What we need to find out now is when the green crabs cease and desist coming out,” said Holt. “That means we can establish when we can plant nets without trapping green crabs underneath them and putting them in a delicatessen.”
“This study will probably change the timing of the planting — it would be a revolutionary change,” he said. “Like putting in winter wheat in North Dakota.”
Warner, who plans on seeding another 50 plots this fall, said he will likely wait until the end of November.
“Everybody wants to do it in the spring because the spring is nice and it’s before the summer, while the clam prices are still down,” said Warner. “Mother nature doesn’t work like that; you have to do it when it allows you to do it.
“If green crabs are active in May and June,” he said, “why would you plant clams under and tuck (crabs) right into a buffet.”
The Heal Eddy restoration project is a unique venture in the region, started in a sub-productive flat whose clam population was decimated by green crabs.
The venture has met with opposition from some local clammers and others who have spoken against leasing flats to individuals which traditionally have been open to a wild harvest.
However, in a July interview with The Times Record, Warner stated he believes the private venture farm model for could be necessary to save the $13 million soft shell clam industry from potential devastation caused by increased green crabs populations.
To view a video of the trapping project, visit http://bit.ly/1x2MStX .