Oyster farmer Jesse Leach holds young oysters at his aquaculture facility on the Bagaduce River in Penobscot, Maine in this 2014 file photo. Credit: Brain Feulner / BDN

Despite the threat climate change poses to longstanding Maine fisheries such as lobsters and softshell clams, and the harm it already has inflicted on northern shrimp and groundfish, there is one Maine fishery that has seen rapid growth in the past decade and is expected to continue expanding: oysters.

Eastern oysters are native to Maine, and have long been harvested as food along the coast, as evidenced by piles of ancient shell middens found along the banks of the tidal Damariscotta River. The river is where the current fishery was revived as an aquaculture enterprise in the 1980s, when growers seeded and harvested hundreds of thousands of pounds of both Eastern and European oysters each year.

Since then the industry has expanded along the Maine coast to Wells in York County and Steuben in Washington County to include nearly 100 commercial lease sites (more than two dozen of which are on the Damariscotta River) and millions of dollars in annual revenues. In 2019, oyster growers earned $7.6 million in gross revenues — more than three-and-a-half times what they took in in 2010 — making oysters one of the most valuable marine fisheries in the state.

Out of 185 permitted commercial-scale aquaculture lease sites listed on the Maine Department of Marine Resources website, 98 are licensed for growing oysters, with many of these also licensed for growing other organisms such as mussels or seaweed. Of those 98, 91 have been approved just in the past decade. That doesn’t include five more proposed oyster sites — three in Hancock County and two more on the Damariscotta River — that are scheduled to be reviewed at public meetings next month.

Bill Mook, who founded Mook Sea Farm on the Damariscotta River in 1985, said climate change has been a mixed bag for oyster growers.

Speaking last week on a panel of experts during a Climate Conversations webinar hosted by the Bangor Daily News, Mook said oysters did not spawn in the river when he first started, but now that the ocean is getting warmer they do. Tiny oyster spat now can foul equipment in the river and has to be cleaned off, he said, but the warmer temperatures also mean that oysters reach marketable size faster than they do in cooler waters.

“It’s not all bad or all good,” Mook said.

One significant challenge to growing oysters in the river was the increasing carbon levels in the ocean, which is aggravated by warming temperatures. The more carbon there is in the ocean, the more acidic it is, which makes it harder for oysters to grow their shells.

Mook said that in 2009, his business suddenly had difficulty getting spat to grow in its onshore hatchery. That winter was unusually warm and, after some investigation, his staff realized the pH levels in the water drawn from the river were too low for the spat to be viable.

The hatchery now treats the water it draws from the river to help ensure the spat is robust enough to be transferred to cages in the river, where they grow to harvestable size.

“It’s like giving TUMS to oysters,” Mook said of counteracting the river’s pH levels.

By cultivating young oysters in hatcheries before transferring them to ocean growing sites, aquaculture operators have a better ability to adapt to the changing climate than traditional fishermen, who depend entirely on Mother Nature for their catch, said Sebastian Belle, executive director of the Maine Aquaculture Association. He also said that because of such nursery operations, and because aquaculture growers use relatively small sites, they tend to be closely attuned to even minor changes in environmental conditions such as temperature, pH levels, or salinity.

“It’s an example of why aquaculture farmers become advocates for environmental protection,” Belle said. Fish farmers routinely collect environmental data firsthand, he said, and have direct knowledge of how their product is affected by surrounding conditions.

Oysters and seaweed have been the fastest-growing sectors of Maine’s aquaculture industry, Belle said.

In the past decade, he said, the introduction of the state’s limited-purpose aquaculture site program, in which licensees are allowed to try their hand growing certain species with certain gear in a 400 square-foot area, has helped fuel interest in oyster aquaculture. Training programs offered by Maine Sea Grant and Coastal Enterprises, Inc. also have helped.

Despite the setback that many businesses have suffered because of the COVID-19 pandemic, he said he expects the industry to keep growing, as long as growers can continue to adapt to the changing climate. Market demand for oysters has increased significantly in the past 10 to 15 years, he said, and Maine-grown oysters tend to fetch a higher price than oysters farmed elsewhere.

And while commercial harvests of species such as baby eels, softshell clams and lobsters are capped or expected to decline as conditions in the Gulf of Maine continue to change, farmed oysters in Maine have better growth prospects than many other fisheries, Belle said.

“It’s a striking trend,” he said.

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Bill Trotter

A news reporter in coastal Maine for more than 20 years, Bill Trotter writes about how the Atlantic Ocean and the state's iconic coastline help to shape the lives of coastal Maine residents and visitors....