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About 30 years ago, Scott Moody was clamming near Harpswell by the Sea when he came across “a monster bed” of shellfish he couldn’t identify.
“What the hell are these?” he asked himself.
He showed some of them to Bob Waddle, a lobsterman and seafood buyer. Waddle recognized them right away: European oysters.
The story of the introduction of these nonnative oysters in Maine begins more than three decades before Moody’s “discovery.” In the late 1940s, the population of Maine’s native oyster had all but disappeared. Known as the American oyster, and also as the eastern or Virginia oyster, its scientific name is Crassostrea virginica. Then, as now, the soft-shell clam population was in decline, probably because of predation by green crabs. Federal and state biologists decided to introduce European oysters to Maine.
Federal biologists figured the species “must have had to fend off green crabs” in its native habitat, said Brian Beal, professor of marine ecology at the University of Maine at Machias. In Maine, they thought, it would either become an alternate food source for the crabs or, if the crabs “wiped out” soft-shell clams, an alternate for harvesters to make money.
The scientific name for the European oyster is Ostrea edulis, which means “edible oyster.” In Europe, it has been a prized food for centuries. European oysters are also known as Belon oysters, after the Belon River in Brittany, France, where they have long been cultivated. In France, only oysters that come from that river may be called Belons.
According to Beal, the seed oysters introduced by American scientists came from the Eastern Scheldt estuary in Zeeland, Netherlands. In the fall of 1949, the young oysters were introduced in several places, but Beal believes the only place they “took root” was Southport Island, near Boothbay Harbor.
“Did they survive? Yes, they did. Did they grow? Yes, they did,” Beal said. But a commercial fishery didn’t develop right away. With native oysters almost nonexistent and the European oyster population so small, annual oyster harvests in Maine remained insignificant. Landings in the 1960s were so close to zero that “you could just barely see a blip” on a graph, Beal said.
‘Dusted all over town’
Despite a slow start for the government biologists’ efforts, a subsequent operation may have produced greater results over the long term. Moody — a lifelong resident of Harpswell, past chair of the town’s Marine Resources Committee and operator of a business that buys soft-shell clams from harvesters — believes he knows how that “monster bed” of European oysters near Cundy’s Harbor came to be.
He said that in 1952-53, Dana Walllace, a Brunswick resident and state marine biologist, led an effort to seed European oysters in Harpswell. At the time, Wallace was assistant director of research with what would become the Maine Department of Marine Resources. Young oysters were “dusted all over town,” Moody said, and Wallace was “leader of the whole thing.”
Waddle had maps, according to Moody, showing where all the European oysters had been placed. Waddle had those maps because he had assisted the biologists by offering the use of his boat to transport the seed oysters to their new homes. “He gave them a ride,” Moody said of Waddle and the baby oysters.
Moody checked out the locations indicated on the maps. “About 95% of those spots had oysters,” he said.
Up until then, “Nobody even knew they were there,” Moody said. But there they were, and plenty of them. However, there wasn’t much of a market for the species.
As Beal explained, “They taste like a penny.”
In Europe, where Belons have been eagerly consumed for centuries, this metallic aspect is considered a good thing. “It’s a flavor that people who like them yearn for,” Beal said.
In America? Not so much. Moody had an answer for that problem: Sell them to European dealers.
He located a Maine company called York Harbor Export that supplied foreign buyers.
“How many can you get?” the dealer asked him. Confident of his supply, Moody replied, “How many do you want?”
‘Diving and dragging’ for a living
There are different ways to harvest European oysters. Unlike American oysters, which tend to firmly attach themselves to hard surfaces like rocks, European oysters can be found in submerged beds, lying loosely on the muddy or shell-strewn bottom. While it is possible to find them by wading the shallows at low tide, harvesters often don scuba gear to pluck them off the bottom, or drag an oyster dredge behind a boat.
Moody sometimes dove for the oysters, but primarily used a boat and oyster dredge. The dredge can be no wider than 3 feet, per Maine regulations, he said. His dredge was small and light enough to be lifted by a single person.
He no longer harvests oysters, but his son does. Like his father, he uses a dredge.
For many years, harvesting oysters was Moody’s primary source of income. He said he raised his four kids on the money he earned “diving and dragging” for oysters.
During good years, Moody said, it was possible to gather 50 bushel bags a day. Today it’s more like 15-20.
Relatively few harvesters have taken up gathering European oysters in Harpswell. Moody estimates that 15-20 people harvest them commercially and only two or three dredge from a boat. “Nobody does it real steady,” he said.
State data for landings of wild European oysters supports Moody’s assessment that few commercial harvesters target the species. According to the Maine Department of Marine Resources, harvesters brought in 21,000 pounds in 2024, valued at just over $55,000.
Unlike clamming, you cannot harvest year-round. Harvesting European oysters is prohibited from June 15 through Sept. 15. There is no closed season for American oysters.
Moody believes the European oyster population rises and falls in cycles of seven years. He said 2026 is at the bottom of the cycle, but he predicted that in two years, harvesting oysters will be “super productive again.”
Hope for native oysters?
The American oyster once flourished along Maine’s coast. The proof is in the huge oyster middens — piles of discarded shells — on the banks of the Damariscotta River. Scientists believe these middens began forming about 2,200 years ago and continued to accumulate for about 1,000 years.
So, if this species of oyster was once so abundant in the wild, why did it decline and almost vanish? No one really knows for sure. But overharvesting, climate change — though not today’s version — and the differing biological traits of the two species almost certainly played roles.
Beal said American oysters fare best in warmer waters. He noted that the middens formed during what may have been a period of warmer temperatures in Maine.
“I think part of the reason (for their demise in Maine) is cold weather,” he said. “The Virginia doesn’t do very well in cold water.”
Darcie Couture is an oyster farmer and marine biologist who serves as Harpswell’s harbormaster. She attributes the disappearance of American oysters mainly to overharvesting by humans.
Couture cited another factor that may have prevented their recovery once the population reached low levels: the way they spawn.
American oysters are broadcast spawners. When temperatures rise in the spring, all the oysters in a bed release their eggs and sperm at the same time. The greater the concentration of spawning adult oysters, the greater the odds that their sperm and eggs will meet to form a baby oyster.
“Once decimated beyond a certain point, they’re not going to be able to reproduce themselves,” Couture said of broadcast spawners. “They need a minimal population density.”
How, then, has the recently introduced European oyster managed to gain a foothold?
European oysters may have a couple of advantages over Americans in Maine’s cold waters. Coming from the cold Atlantic coast and the estuaries of northwest France, they are well suited to the temperatures of Midcoast Maine.
The spawning methods of European oysters may also give them a slight advantage. Female Europeans do not broadcast their eggs. “They brood their larvae,” Beal said.
The females keep their eggs in a pouch within the shell and bring sperm-bearing water inside. Fertilized eggs remain inside the pouch for two weeks before being released as free-swimming larvae.
Perhaps the extra bit of maternal care could help small, relatively scattered populations of European oysters slowly but gradually increase in size.
“Brooding certainly increases the chance of overall survival,” Beal said. But he cautioned against making too much of that approach. He noted that there are many species that have used the broadcast strategy to survive for millions of years.
Despite some disadvantages, American oysters can thrive across a wider range of conditions than Europeans.
Europeans must stay immersed because they cannot tolerate the higher temperatures that exposure at low tide can bring. Americans, which close their shells tightly when out of the water, can.
In sum, the Americans are tough and the Europeans are delicate, according to Couture. Consequently, Europeans are only found in places that meet their more particular needs.
“European oysters must stay fully submerged throughout the entire tidal cycle, which is why you find them in tidal pools and shallows around the edges of the islands and shorelines in Harpswell,” Couture said.
Still, they are fairly widespread in Harpswell. With the help of harvesters, Harpswell has developed a map showing 570 acres of European oyster beds “all through town,” Couture said.
These days, the intentional introduction of a nonnative species into the marine environment by anyone, let alone scientists, would be considered highly improper.
“Now you would be shot to bring in a nonnative species,” Couture quipped.
There is a ray of hope for the wild population of American oysters here. While they are scarce compared to Europeans in Harpswell, Americans can be found. Moody reports that in Brunswick, “Thomas Point is infested with them.”
It’s perhaps ironic that the increase in the wild population of native oysters is most likely the result of aquaculture. The sprouting of oyster farms in the Midcoast has created new sources of oyster eggs and sperm released into the water every year. The species of choice in these farms is Crassostrea virginica, the oyster of the ancient Midcoast middens.
Couture believes the wild American oysters here are the descendants of these farmed oysters. “That’s the only source they could have come from,” she said.
