College of the Atlantic student Emma Ober checks on an area of clam flats where the town’s Marine Resources Committee has been conducting experiments to see why the flats have been less productive in recent years. PHOTO COURTESY OF CHRIS PETERSON

How do your clam flats grow? Project to boost clam numbers underway



BAR HARBOR — For a few years now, members of the town’s Marine Resources Committee have felt “like border collies running out of sheep” to protect, says Scott Swann, who chairs the committee.

Their job is to protect the town’s clam flats for recreational clammers and the handful of folks who make part of their living digging clams. And the population of market-sized clams is declining.

Last month, the committee applied for a grant for a project they’re hoping will help some clams grow big enough that they’re less vulnerable to predators.

“The last few years have been very frustrating for us as a clam committee,” Chris Peterson, the committee’s secretary and a biology professor at College of the Atlantic, wrote in the grant application. “Bar Harbor’s clam flats have become less productive, and as our larger clams are harvested, we do not seem to have any small clams coming back to replace them.”

The life cycle of a soft-shell clam begins when adult clams, buried in mud, release gametes (reproductive cells) into the water. Fertilized eggs grow into larvae and float as plankton, then settle into the mud to grow and mature. When a clam settles it’s still very small, only about twice the thickness of a human hair.

“We’ve had incredible recruitment (juvenile clams settling out of the water into the mud),” Swann said, “but then they disappear. It’s like a Stephen King movie where all the children are getting kidnapped or something.”

The committee has been conducting small-scale experiments to learn more about the change. The evidence mostly points, they say, to the juvenile crabs being eaten by predators, especially invasive green crabs.

These experiments have included setting out wooden boxes with mesh to protect the clams from crabs and other predators. These are some

Fine mesh netting that can exclude crabs but still allow clams to put up their siphons spread over an area of the clam flat. The perimeter of the net is buried 6-8 inches into the mud. PHOTO COURTESY OF CHRIS PETERSON

times called Beal boxes in honor of Brian Beal, the University of Maine at Machias professor who invented them.

In other areas they’ve laid down sheets of fine mesh netting that can exclude crabs but still allow clams to put up their siphons. The perimeter of the net is buried 6-8 inches into the mud. The committee has permits from the Army Corps of Engineers to set up these nets, according to the grant application.

“We’ve been doing this on a small scale with stunning results,” Swann said. They’ll find lots of clams in the protected area, and none in the area outside of it.

“To date we have only used this to assess recruitment,” Peterson wrote in the application, “and after counting the seed they are spread back over the flat unprotected.”

PHOTO COURTESY OF ACADIA AQUA FARMS

“We’ve got these thousands of baby clams,” Swann said, “and then just scattered them back in the ocean where there’ll get eaten.”

The planned project involves a new step: they’ll collect the juvenile clams from the protected sites on the mudflats and move them into mesh nets that hang in the water in aquaculture sites to grow a bit bigger. Then the following spring the group will re-seed some areas of the mudflats with the larger clams. Some of them will again be protected from predation with netting.

“You can only raise them until they’re about three-quarters of an inch in these hanging things, and then they stop growing,” Swann said. “They need to be planted.”

The project will use two or three local aquaculture sites: one is a limited purpose, lease site operated by College of the Atlantic for research and educational purposes near the college, one of the Acadia Aqua Farms lease sites and potentially a site in Blue Hill Bay leased by committee member Matt Gerald. All of the sites have this activity allowed as part of their current lease agreements, according to the committee.

“The work is not being done at a scale that we expect to produce any academic publications,” Peterson wrote, “the main purpose of the work is to share our insights with our local community and the broader clam community.”

Swann said the committee should know soon whether the $7,200 grant from the Maine Shellfish Restoration and Resilience Project will be awarded. The grant program is part of a collaboration between the Broad Reach Fund of the Maine Community Foundation, the Maine Shellfish Advisory Council and the University of Maine.

The Bar Harbor Town Council agreed last month to have the town act as fiscal agent for the grant.

The budget includes materials, use of a boat to access the aquaculture sites and compensation for a college intern working as project coordinator and for clammers working on the project. High school students will be invited to help in field work days. The aquaculture farmers helping with the project are donating use of their leases and their time, according to the application.

“It’s a great community project,” Swann said, bringing together COA, local clammers and the high school.”

 

 

Liz Graves

Liz Graves

Reporter at Mount Desert Islander
Liz is an award-winning journalist who has been with the Islander since 2013. She grew up in California and came to Maine as a schooner sailor. [email protected]