Robert Boyce gives a thumbs-up as he leans over a boat full of clams.

Digging for wild shellfish in the intertidal is one of the oldest traditions along the Maine coast. Shellfish provided a food source for the first inhabitants of Maine and continues to do so in the present day. On the surface, it seems like a simple activity. You look for holes in the mud, dig down, and pull up some clams. But there is a lot more to both the harvesting of clams and the management of the resource.

While long ago, people harvested shellfish just to feed their friends and family, now there is a commercial fishery that employs close to 1,500 harvesters and is one of Maine’s most valuable marine resources, bringing in over $24 million in 2020, according to the Maine Department of Marine Resources. The harvest is dominated by soft-shell clams, but also includes quahogs (hard-shell clams), razor clams and oysters.

In Harpswell, as in many towns, the shellfish resource is managed by the local Marine Resources Committee, which is composed of harvesters, community members and the town’s marine resource administrator, Paul Plummer.

Harpswell’s shellfish industry employs a significant number of people, including 49 resident and six nonresident diggers. That doesn’t include 11 student and eight senior licenses that have been allocated, nor does it include the dealers, processors, seafood markets and restaurants that buy and sell shellfish.

That total value is hard to measure, but the value of the landings in Harpswell is easier to quantify. Local diggers harvested nearly 173,000 pounds of soft-shell clams worth about $420,000 in 2020, making Harpswell the 12th-ranking town in the state for soft-shell clam landings, according to the DMR.

While shellfish harvesters continue to employ traditional tools and methods, much has changed over time. One of the biggest shifts in Harpswell, as well as in other parts of the state, has been the rise in the quahog population.

Between 2008 and 2020, Harpswell’s quahog landings grew from less than 30,000 pounds to more than 230,000 pounds, worth more than $400,000. That 2020 number made Harpswell the third-highest-ranking town for quahog landings in 2020, behind nearby West Bath and Brunswick.

Harvester Robert Boyce has been clamming in Harpswell for more than 30 years.  “Clamming’s been good here for a long time, but when the worms and crabs killed the soft-shells off, the quahogs showed up, and thank god for that,” Boyce said.

Several factors may be contributing to this shift in species, including the introduction of green crabs to the Maine coast. European green crabs have been in Casco Bay since the 1900s, but the predators have exploded in numbers in more recent years, decimating the soft-shell clam population.

Green crabs impacted the quahog population as well, but quahogs’ thicker, tougher shells can withstand some of the voracious green crabs’ efforts. The reduction in the soft-shell population also opened up new habitat for quahogs that wasn’t previously available.

Milky ribbon worms are another ravenous predator that has wreaked havoc on soft-shell clam populations. They aren’t invasive, but they are prolific and destructive.

Changing water conditions have also played a role. As the ocean grows more acidic, the acidity hampers shell growth and erodes existing shells, according to the National Oceanic and Atmospheric Association’s Acidification Program. This increase in acidity has a greater impact on soft-shell clams, which have thinner shells.

Acidification results from increases in carbon dioxide, one of a suite of greenhouse gases that are causing the planet and its oceans to warm. Water temperatures have risen dramatically in Casco Bay — at a rate 99% faster than the rest of the world’s oceans, according to the Gulf of Maine Research Institute.

Changes in water temperature are causing shifts in where species live. Quahogs were once much more common further south, but are marching their way northward as the temperature forces them to shift habitats.

In an effort to help the quahog resource along, the town of Harpswell has been growing quahogs in a tidal upweller. The purpose is to grow quahogs “until they reach a size that is less susceptible to predation,” then transplant them onto the mud flats, Plummer said.

“Harvesters are seeing climate change happening in front of them and they are beginning to embrace it and look towards ways to use it to their advantage,” Plummer added.

Those harvesters include Boyce and his son, who also holds a commercial shellfish license. Together, they have applied for an intertidal aquaculture lease to grow quahogs.

One non-environmental challenge that has intensified in recent years has been the increase in development along the coast, which has limited harvesters’ access to the flats.

“Harpswell’s shorefront market exploded in 2020 and some of these new owners are restricting access to the flats through historic walking paths,” Plummer said. “This makes it harder for the harvesters to get to the flats to earn their living.”

Boyce has witnessed these changes.

“You might park five years in a row on someone’s road and then one day you walk down the road and someone yells at you because the house sold to someone new and they don’t want you there,” Boyce said. “You can apologize, but it’s tough.”

The lack of access along the shore causes safety concerns for diggers, who then must travel further to return to shore — sometimes in blustery, cold, dark conditions.

“My wife started digging when she was about 40,” Boyce said. “She always says she wishes someone could see what it’s like to be out at low tide at night and wish that you could land where you used to, but now you have to go 4 miles further in the dark, cold. It’s really dangerous.”

Whatever challenges lie ahead for Harpswell’s shellfish resource, it is clear that the harvesters and the town are invested in its future. As the climate changes, so too does the approach to management of the resource and the tools used to continue this valuable tradition in Harpswell and other towns across Maine.

Susan Olcott, of Brunswick, is Director of Operations for the Maine Coast Fishermen’s Association. She has a weekly column, “Intertidal,” in The Times Record, and writes for Maine Women Magazine.

A grant from the Broad Reach Fund supports the Harpswell Anchor’s reporting on the working waterfront.