The Green List: Farmed Shellfish


These shellfish are all filter-feeders that are extremely well-suited to aquaculture. There is little to no risk of pollution or escape, and the effects to surrounding habitat from farms are limited. These filter-feeders actually benefit the surrounding coastal waters by filtering them, and don’t rely on wild fish or fish meal for food. Diseases are extremely rare, so antibiotics and chemicals aren’t necessary.

Farmed Oysters
Ninety five percent of oysters worldwide come from aquaculture operations. They are cultured in 46 countries, with China, Korea, Japan, The United States and France as leading producers. Through their filter-feeding action they improve coastal water quality by converting nutrients and organic matter to biomass, reducing the bacteria, zooplankton, and phytoplankton in the water column. They are typically harvested using dredges or hand-harvesting, and although oysters grown suspended are considered more sustainable, those that are harvested through dredging have less impact per unit than dredging of wild oysters.

They are bivalve mollusks, with two shells held together by a thick muscle. They do not move, making escape impossible. Oysters are typically prepared fresh and served raw, often with just lemon or a mignonette sauce. The flavor is often described as salty and complex with a delicate aftertaste. They can also be prepared in shooters with Tabasco or liquor, or in a dish called Oysters Rockefeller where they are cooked with cheese and bread crumbs. Smoked, fried and cooked oysters are also offered at restaurants. Try out celebrity chef Paula Deen’s Spicy Oyster Shooters for an example of one preparation.

Farmed Mussels
Nearly 89% of the world’s mussel production is from aquaculture with the major production areas in China, Spain, Italy, Thailand, France, and New Zealand. The United States is a small producer of mussels, and imports them primarily from Canada and New Zealand. Like oysters they can be cultured on-bottom or by suspension techniques, which account for 85% of production. There are very few outbreaks of diseases, and so chemicals and other antibiotics are rarely used.

Like oysters and clams, mussels improve water quality through filter-feeding, and because it is not necessary to feed them, mussel farming does not increase nutrient input to the water. They use the bacteria, phytoplankton, organic detritus and other material in the water as food. They can remove particles as small as 2 to 3 µm from the water with 80% to 100% efficiency.

The most common species of mussel is the blue mussel and they can grow from 5-10 cm. Mussels are bivalves with two shells that are triangular and elongated and can be purple, blue or brown. Blue mussels have the ability of detach and reattach to a surface, allowing them to reposition themselves during tidal changes.

The most common way to prepare mussels is to steam them until they open and then add a sauce. They have to be thoroughly cleaned before cooking, and those that do not open through steaming should be discarded. Mussel meat is rich and sweet and the color can range from white to orange. They have a beard, which they use to anchor themselves, and it should be removed before preparation. Try this simple and delicious mussel in white wine dish from The Barefoot Contessa.

Farmed Clams
These farmed bivalves make up 89% of the world’s clam consumption, with the majority being produced in the United States. Similar to oysters and mussels, clams do not require fertilizers or feeds, so nutrient addition to coastal waters does not occur. They can remove viral and bacterial particles from the water, improving water health.

Management of the clam farms is considered highly effective, especially when mechanical dredges are not used. Clams are composed of a mantle and a foot which can serve as a digging mechanism. They feed on particles in the water, requiring no additional feed. The major species of clams for production are the Manila clam, the razor clam, the blood cockle, and the northern quahog. The two most common methods of growing clams are ground plots and tray culture, both of which occur on the sea floor. They are harvested by hand in the US and Canada, although there are some areas that use dredging methods in other countries.

Farmed clams are available year found. They can be eaten raw, steamed, boiled, baked or fried. Clams, like mussels, should be discarded if they do not open while being cooked. The meat can range from white to pink tones, and provides its own salty juices when cooked, bringing out the delicate, sweet flavor. Try this recipe by celebrity chef Anne Burrell of Linguine with White Clam Sauce.

Farmed Scallops
Although almost 96% of scallops consumed in the US are wild-caught and not always sustainable, those that are farm-raised are on the Green List. If you encounter farmed scallops, they are likely raised off-bottom (above the seabed) in the US or Canada and  are a sustainable Best Choice. However, the small percentage of farm-raised scallops that are imported from China or are dredged from the seafloor are an exception, and cause greater environmental damage. Because scallops are filter-feeders, they remove and consume particulate matter from the surrounding water, improving water quality. There is also no risk of escape to wild stocks and when farmed off-bottom there is no risk of pollution or habitat effect.

There are more than 360 species of scallops but only 15 of those are used for farming. Because off-bottom culture and harvest of scallops is far more wide-spread than the far more unsustainable bottom-culture, those scallops that are farmed are termed sustainable. The scallops that are US farmed (or from any nation other than China) are designated as a “Best Choice” by Monterey Bay Aquarium, and when found in restaurants would be recommended to eat.

Scallops are available year round and have a firm texture with a mild, sweet flavor. They are delicious seared or poached, with a delicate sauce. Try this Bay Scallop Gratin from Barefoot Contessa, Ina Garten.

Photos by Peter Gugerell, Akigka, childofmidnight, and svdmolen, via Wikimedia Commons, Creative Commons License

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