I was in New Orleans last week and I must say, I sure ate a lot of oysters. I ate them raw, grilled, roasted, and fried in po-boys, and on crisp salads (the fried oyster salad is a thing of beauty). Between bites, slurps, and crunches, I got to wondering about the sustainability of oysters. I knew that they’re listed as a "best choice" in many seafood sustainability guides, such as the Monterey Bay Aquarium Seafood Watch, but I didn’t really know why, so I thought I’d find out.
Most oysters available these days are farmed. Unlike some types of aquaculture, oyster farming requires pristinely clean waters and a deep understanding of tides, water temperature, and other factors that affect the oyster bed’s health, meaning there is almost no way to farm oysters irresponsibly.
Oysters are filter feeders. They don’t require the manufacture of food or the harvest of other sea creatures to feed them, eliminating the possibility of contaminated feed that exists in some aquaculture operations. Also, unlike salmon and other carnivorous fish farming operations, raising oysters does not result in a wasteful net loss of protein. Because oysters are filter feeders, they actually clean the water, encouraging more light and the resultant growth of ocean greenery and increase in oxygen levels. Not only do oysters clean the water, but the oyster farmers must act as protectors of the environment in which they farm, or they would be out of business.
What to look for in an oyster:
The flavor of a good oyster is clean and fresh, like the sea. Depending on the species, it may be a bit sweet, or have a minerally tang, a buttery richness, or the refreshing cool taste of a cucumber.
Oysters are farmed widely in Washington, Maine, northern California, and the Gulf Coast. They oysters I was eating in the gulf are big ones, most likely the American oyster. In California and Washington, you’ll find many other varieties, from the European Flat, to the tiny, delectable Kumamoto, to the petite but bold Olympia and the clean, seawater-flavored Pacific.
Interesting Trivia: It is said that oysters shouldn’t be eaten in months without Rs (May, June, July, August) because when the waters are warm, an algae bloom, or "red tide", can occur, causing shellfish that live in the water to become poisonous to humans. But the main reason not to eat oysters during the warm summer months is because that is when the oysters spawn; all of their energy is devoted to reproduction and their flesh becomes soft, dull, and often distasteful. You can spot a spawning oyster by the milky, instead of clear, liquid surrounding it.
Source: Fish Forever, The Definitive Guide to Understanding, Selecting, and Preparing Healthy, Delicious, and Environmentally Sustainable Seafood by Paul Johnson. (Wiley 2007)