by Rachael Manasseh, Center for Environmental Farming Systems Intern 2022

Known for their unique color and mushroom-like flavor, green gill oysters are a marine delicacy found in very few water environments. One of these is along the coast of Marennes-Oléron in France, where these oysters are harvested in small ponds or “claires”. Another prime spot, perhaps surprisingly, are the sounds and reefs in eastern North Carolina, which have become an ideal home for green gills.

Oysters feed on algae among other things. One algae in particular, Haslea Ostrearia, is responsible for the blue-green coloration of oyster gills. This type of algae grows best in colder waters and contains a pigment called marennine that stains the gills of oysters as they filter the surrounding water. Recent studies on marennine have suggested that it may have antioxidant properties and other health benefits, as well as potential use in food and cosmetic industries.

“They’re unique in that there are only a few specific bodies of water that seem to produce the algae that produces the green-gill feature,” says Ryan Speckman, co-founder of Locals Seafood. “Before Hurricane Florence, green gill was relatively predictable in certain bodies of water throughout the NC Coast. It seems to be most prevalent in winter when the coastal waters clear up and sunlight can hit the estuary floor. Post Hurricane Florence, the phenomena seems less predictable, and completely absent in many bodies of water where it was historically prevalent.”

They say that people “eat with their eyes”, and for many years the visual appearance of green seafood made these oysters much less appealing. Although green gills had been savored in France for centuries, it was more of a challenge to convince consumers in the States that these oysters are edible, and even delicious. Harvesters often had to sell their catch at a discount or resort to throwing them away. But in recent years, chefs and local retailers have gotten creative in promoting green gill oysters, which in turn has boosted their popularity in North Carolina.

“To me, they are similar to shad roe or soft shell crabs in that they are only available a brief time, if that,” says Sarah Grace Smith, Director of Growth and frequent shucker at Locals Seafood. “I’ve always enjoyed shucking them for their beauty and the connective feeling they give me to the coast. Green gills are visually representative of what is happening in the sounds and rivers 200 miles to the east.”

If you want to try these unique oysters for yourself, be sure to connect with local harvesters and fishmongers during the winter and early spring months. Green gills are a seasonal treat, so keep your eyes open for their distinct color before the waters warm up again.

To read more about green gill oysters, check out these resources:
Atlas Obscura – Green Gill Oysters

National Library of Medicine – Marennine, Promising Blue Pigments from a Widespread Haslea Diatom Species Complex

Sandbar Oyster Company

Tasting Table – Green-Gilled Oysters Are Being Cultivated In North Carolina