Warming seas are making Maine more hospitable to hardshell clams.
In this June 7, 2022, file photo, David Wilson of Harpswell digs hardshell clams in the intertidal mud on Middle Bay, near the Brunswick town line. Credit: Troy R. Bennett / BDN

This story is part of Maine Public’s series “Climate Driven: A deep dive into Maine’s response, one county at a time.”

It was the first official evening of spring and Mike Gaffney was ankle-deep in the mud of the tidal flats of his Georgetown oyster farm with two researchers.

The trio weren’t there for oysters — a delicacy at the center of an aquaculture boom in Maine — but were, instead, checking on an experiment that some hope could help usher in a new industry in the state. Half-buried in the mud were about a dozen mesh bags and crates containing thousands of tiny hardshell clams, also known as quahogs.

“I have to say I am really glad to see them all here because we did have a period of really cold weather,” said Marissa McMahan, director of fisheries at Manomet, a scientific nonprofit studying how climate change is affecting species in the Gulf of Maine. “There’s a bridge down there that you can see. I would drive by and look into the cove and see ice everywhere. And it was like, ‘Oh no, I hope those bags are still here.’ So this is great!”

Quahogs are native to Maine but are more commonly associated with southern New England and the even warmer waters farther down the Eastern Seaboard. But as the global climate changes, the Gulf of Maine is heating faster than almost every other part of the ocean around the globe, according to researchers. And that temperature shift, along with other factors, may be making Maine more hospitable to these harder-shelled cousins of the softshell clams that have been a major part of the state’s fisheries industry for decades.

“They’ve been here in pockets in low abundance for a while but now we are starting to see — especially some places in Casco Bay in particular — where they are just really thriving and becoming incredibly abundant,” McMahan said. “So the idea is that the timing, we think, is right for doing this kind of experiment and seeing if this is actually something that could be viable.”

Hardshell economics

The federally funded experiment is researching best methods for growing quahogs in Maine — where tidal flats are scoured by ice during winter — both for aquaculture and for expanding wild populations. Manomet is working with Gaffney, who runs Eros Oyster with his son in Georgetown, as well as other shellfish farmers and officials in nearby Brunswick.

“It’s really, can we grow quahogs in the intertidal at a growth rate that is profitable for oyster farmers to get them to market?” said Batchelder, fisheries project manager for Massachusetts-based Manomet, while standing on Gaffney’s tidal flats. “We know we can grow them out on the oyster farm but it just takes too long to financially make sense for a lot of farmers.”

Added Gaffney: “I’m curious on the biology side, the farming side and on the marketing side. And I just think it’s fun to do.”

If successful, quahog aquaculture could help oyster farmers as well as traditional softshell clam diggers diversify their businesses.

In the mid-1970s, more than 30 million pounds of softshell clams — also known as steamers — were harvested and sold by commercial fishermen each year along the Maine coast. Today, that figure has shrunk to just 6 million pounds as climate change created ideal conditions for green crabs and other predators.

Quahogs have harder shells that can close tighter than softshell clams, making them more resilient against the ravenous green crabs that now plague many parts of Maine’s southern coastline. While softshell clams remain a significant industry in Maine, many of the historic softshell clam flats have been decimated by the invasive crabs and diggers are finding it increasingly hard to access other flats as new landowners close off intertidal areas.

Building resiliency

Kevin Madley, regional aquaculture coordinator for the National Oceanic and Atmospheric Administration in Gloucester, Massachusetts, said that development of new aquaculture sectors can help fishermen overcome some of the challenges created by climate change as species that were once abundant start to decline. And he said Maine’s softshell clam industry, which has been hit hard by green crabs, is one of those that could benefit from alternative markets.

“One of the things that NOAA focuses [on] is diversification of opportunities to be more resilient,” Madley said. “We don’t necessarily know what all of the changes are going to be throughout the next few decades. One of the things we are trying to do is get ahead of that and forecast what the changes are. But offering these other opportunities by supporting new sectors is a way to be resilient independent from what those changes are going to be.”

Quahogs are big business in states like Virginia, where federal data show fishermen harvested nearly $58 million of the clams in 2021. Quahogs also brought in an estimated $14 million that year in Massachusetts, which has a growing quahog aquaculture industry. Maine’s wild and farm-raised quahog harvest is small, by comparison, but has increased more than sixfold during the past decade.

Gaffney was a willing partner in the Manomet project, which is funded by a U.S. Department of Agriculture grant.

He has been growing oysters for about six years in the tidal river that flows by this secluded spot on Georgetown Island, a few miles from Reid State Park. Eros Oyster sells about 400,000 of the prized shellfish that Gaffney and other local oyster farmers grow for restaurants and other buyers throughout the region. They are part of a booming industry that now has about 150 oyster farms up and down the coast.

Gaffney said his phone began ringing a few weeks ago with restaurants asking for oysters — and anything else he could supply.

“My customers are always calling and saying, ‘Well, what else have you got?’” he said. “I say, ‘well, we’re monoculture. We’re oystermen.’ But there’s no reason why we can’t do more.”

Riding oyster coattails

Back in the fall, the team placed about a dozen mesh bags and plastic crates in the nutrient-rich tidal flats on Gaffney’s property. The bags and crates are both used in the oyster industry, where the shellfish are grown over several years in floating farms. But initial experiments suggest quahogs don’t grow as fast or as well in that setup than in the tidal flats.

Each container started with between 400 to 1,000 quahogs. And while they wouldn’t know for a few more weeks how the young shellfish did over the winter, there were promising signs on this particular evening. While ice had moved or dragged some of the bags, Batchelder and McMahan could clearly see quahogs in the enclosures.

Gaffney said he recently read an account by a Florida oyster and quahog farmer who said he estimated he can grow 10 hardshell clams for the same effort that goes into each oyster. The latter currently fetch more money and growing quahogs in Maine will require overcoming logistical and weather challenges that aren’t as severe further south.

But Gaffney said that if shellfish farmers can “set ’em and forget ’em” in the mudflats without frequent maintenance, such as frequently digging up the enclosures or moving them in winter, he said many farmers might just give it a try.

“I haven’t had any to sell yet but, like I said, I get a lot of calls for them,” he said. “And I suspect that they’ll ride the coattails of oysters. The farmers have made the sales connection.”

Manomet plans to study quahog aquaculture on Gaffney’s property for the next several seasons.

This article appears through a media partnership with Maine Public.