Can Farming Save the Clam Fishery?

by Sarah Craighead Dedmon

Clam from the Rim River damaged by green crab. Sarah Dedmon photo

2016 saw Maine’s lowest clam landings since the 1950s. “At that point in time, sea water temperatures warmed for four years in a row to about the same level they are today,” said Dr. Brian Beal. “Green crabs came in and ruled the roost.”

As softshell clam landings took a nosedive, Mainers responded to the green crab crisis by starting a new fishery. They imported European oysters from Belgium in hopes they might coexist with the green crab, which also came from Europe more than a century ago.

Though descendants of those original European transplants still remain in Boothbay and the Sheepscot River, a full fishery never took root and as luck would have it, it didn’t need to. Temperatures soon returned to normal, the green crab threat receded, and clam landings began climbing once again.

But Beal doesn’t think towns should hope that will happen again, noting that the Gulf of Maine is currently warming faster than 99 percent of the world’s oceans.

“You look at the trend,” said Beal. “There’s variation, but the [warming] trend is moving up. You have to think like a predator.” Because the clam’s predators are mostly cold-blooded, when water temperatures rise, they eat more and have more offspring.

“So, it’s a formula for disaster if you don’t do anything about it,“ he said.

Recruitment boxes at Collins Cove, Freeport, ME. Boxes measure 1 foot x 2 feet, set out on clam flats. Mesh on top prevents green crabs from entering. DEI photo

Beal serves as research director for the Downeast Institute for Applied Marine Research and Education (DEI). He said he thinks clam committees could get more bang for their conservation efforts by changing their strategies, which sometimes address overharvesting better than predation.

“They could remove every single clam [in a flat], and there would still be a rain of clams coming down,” said Beal. “There is a population of clams that are spawning, and that is what is driving the commercial catch.”

But what’s driving low clam survival rates is a battle that’s happening on a scale undetectable to the human eye.

Clam spat measure roughly one quarter millimeter across when they settle on the ocean floor, and there they are devoured by green crabs four times their size, measuring one full millimeter across.

“That’s where the murder, the intrigue happens,” said Beal. “That’s the level that’s going to affect commercial landings.”

Beal Boxes

In the southern and central part of the Maine coast, softshell clams are fighting a war on two fronts — green crabs attack from above, and milky ribbon worms attack from below. Beal designed a study to measure wild clam recruitment on the Haraseekeet River in Freeport using small wooden boxes with fine mesh protecting the top and the bottom. The boxes are now known as “Beal Boxes.”

He laid the boxes at 10 sites on the west side of the Harraseekeet, and 10 sites on the river’s east side. Some of the boxes were filled with sand, but most were left empty and settle onto the mud flats in April, then collected in November.

In Beal’s words the results were “absolutely fantastic.” Data showed that the boxes on the east side had much higher clam populations than the west side boxes, possibly due to the prevailing winds. But all caught significant numbers of clam spat.

One of the boxes from the east side contained more than 3,000 wild clams per square foot, and the spat of twelve other species besides, including Quahogs, American oysters, European oysters and blue mussels. “They told me this was dead mud. Dead mud!” said Beal.

And how many clams were found in a sample taken just outside the box?

One.

Clam Farms

Knowing that the clam spat are out there, Beal thinks there might be a way for harvesters to continue earning despite declining wild populations. What if, he suggests, coastal towns lease small parcels of their mudflats for commercial harvesters to operate as a clam farm?

In 1911 the Maine legislature passed a law allowing municipalities to lease 25 percent of the clam flats within their town limits. “That kind of information was lost,” said Beal. In a town like Machiasport which has 1,400 acres of intertidal zone, a three-acre parcel assigned to every harvester would still leave nearly 90 percent open for wild harvesting.

Ethel Wilkerson is also intrigued by the idea of small clam farms run by individual harvesters. As the Senior Program Manager for Manomet’s Softshell Clam Aquaculture Program, Wilkerson said that Manomet is currently conducting research to learn how many clams can fit under one net and still grow at a reasonable clip. Manomet is a Massachusetts-based nonprofit with offices in Brunswick.

“The more dense the clams, potentially the slower they will grow,” said Wilkerson. “We’re trying to hit that sweet spot.” In southern and central Maine clam spat take three years to reach market size, and Downeast it can take four.

“If we can get a dense amount of clams under a net, then when the price is high [the harvesters] go there, or maybe right before Christmas, kind of like a bank,” said Wilkerson. “You know when they’re ready, when you can go and that they’re safe from some of the predators. I don’t see it as a mechanism to replace wild harvest entirely.”

Beal likened the concept to a lobster pound. Clam harvesters could could carry their “inventory” through periods when the price of clams is low, and choose to sell it when the price is high. In between, they could continue wild harvesting in their town’s open flats.

Obstacles

Wilkerson said that most clam harvesters are familiar with the seeding process now, but the cultural transition from a municipal effort to individual farms could be a knotty one.

“Once you put down gear, it switches from the fishing, fowling and navigation framework to aquaculture,” said Wilkerson.

Both Beal and Wilkerson said that the legal obstacles to setting up small clam farms for harvesters are significant. In addition to requiring approval from the Maine Department of Resources (DMR) as with any aquaculture lease, private aquaculture leases also require approval from the riparian landowner, due to Maine’s intertidal ownership laws which place ownership at the low tide mark.

“For a lot of municipalities, the reason they’ve been able to do this conservation effort in broader farms is because it’s a cooperative agreement,” said Wilkerson. “They say, ‘We’re not going to go in there until we’re all ready.”

But if only one or two harvesters want to install a clam farm, Wilkerson said they should wait until they have a legal mechanism to stop other harvesters from taking their clams, which would require regulations at the state level.

Further Research

With landings of $15 million in 2016, the softshell clam fishery is the third largest in Maine, behind only lobsters and Atlantic herring. Beal said he would like to see the state designate research as one of the purposes of the Shellfish Fund, as it is with the lobster, scallop, elver and sea cucumber funds.

“This is why there’s not more softshell clam research going on in the state of Maine,” said Beal, who works to secure DEI’s funding through grants from the federal government, private philanthropists, and educational institutions.

DMR Director of Communications Jeff Nichols confirmed that the shellfish fund is not really used for research. “The department would have to issue a “Request for Proposals” that a researcher could respond to, in order to apply for funds,” wrote Nichols. “However, the department does not issue RFPs for this fund, as it is used exclusively to fund the staff within the municipal shellfish program.”

“What else can we learn about this industry? What else can we learn to enhance and sustain?” said Beal. “Well, that’s research, it’s applied research. And that’s what these [other] funds are set up to do.”

Beal said that if Maine doesn’t change its strategy for the softshell clam and sea temperatures continue to rise, it could be disastrous for the fishery.

“There’s nothing you and I can do, or the town of Machiasport, or even anything the state of Maine can do about the warming Gulf,” said Beal. “We either adapt to the changes that are happening, or we lose.”

UMM’s Marine Science Field Station at www.downeastinstitute.org