Bottom-grown oysters are purged in the Damariscotta River, the heart of Maine’s oyster growing industry, before being harvested. (Photo Courtesy Pemaquid Oyster Company)
Bottom-grown oysters are purged in the Damariscotta River, the heart of Maine’s oyster growing industry, before being harvested. (Photo Courtesy Pemaquid Oyster Company)
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Maine oysters are well on their way to sharing the stage with lobsters as a signature seafood from the state of Maine, according to Chris Davis, director of the Maine Aquaculture Innovation Center.

The Damariscotta River is the heart of the historic oyster-growing region, and that's where oyster farming sprang up in the 1980s. The estuary produces firm, briny oysters with a clean, bright taste that quickly became popular at local midcoast restaurants.

The industry is not so local anymore. These days there are 75 oyster farms in Maine coastal and estuarine waters, from Saco to Washington County, and Maine oysters - particularly Damariscotta River grown oysters - are a popular menu item in white-tablecloth restaurants along the East Coast and the Gulf Coast. They are also shipped around the world.

"There is phenomenal market demand for Maine oysters," said Davis.

Every farmed oyster in Maine is raised from baby oysters, known as spat, that are grown in one of two hatcheries in Maine. When the youngsters are put out into Maine waters, they grow to harvestable size in bags or in cages on floating gear that gives them some protection from prowling predators, like starfish and whelks. Alternatively, they are put on the bottom to grow out to market size where they need less care but are more apt to be eaten by predators.

It takes from two to four years from spat size to being served on the half shell with lemon on ice.

But it's not all pearls. Diseases can wipe out a crop, as the bacteria known as MSX did to some growers in the past few years. MSX is deadly to oysters, but doesn't affect people.

Oyster breeding for disease resistance has helped tackle some problems, but others are on the move.

Vibrio, another warm-water bacteria, caused a handful of people who ate raw oysters in Maine during the summer to get sick in the past couple of years. Vibrio is a real concern because, while still rare in raw oysters grown in warmer waters, it can be fatal to older people and those with underlying health concerns like diabetes. Handling and cold storage of the oysters appears to be very important in preventing Vibrio bacteria from spreading.

Maine Sea Grant, the outreach marine education arm of the University of Maine, recommends that oyster growers buy their spat from in-state nurseries to avoid introducing pathogens from away.

And, as cold coastal waters get slightly warmer, invasive green crabs hoover up young oysters as easily as they do clams. The Chinese mitten crab, as big as a rock crab and as voracious as a green crab, is also on the march north, according to researchers from the University of New Hampshire. It has not yet arrived in Maine, but is expected, and when it does, it may pose a serious challenge to the shellfish industry.

Still, it doesn't take a lot of overhead to get into the business in a small way and the industry is solid gold right now, generating $4.5 million for the Maine economy each year and employing 150 people directly in oyster farming.