Oysters on the half shell are a type of bivalve mollusk that have been opened, or shucked, for consumption. Oysters on the half shell are typically served raw with a variety of condiments. They may also be lightly steamed, broiled, or baked with various seasonings.
Oysters belong to the family Ostreidae, native to saltwater oceans and bays, and to brackish coves all over the world. Oysters on the half shell, however, often come from commercially-farmed oyster beds or reefs. Oysters for consumption on the half shell are distinctly different from those cultivated to produce pearls, although they may occasionally produce vestigial pearls.
In the United States, five types of oysters are commonly served on the half shell. Virginica oysters, native to Atlantic waters from Canada to South America, include Blue Point oysters, Chesapeake Bay oysters, and Malpeques oysters. European, or Belon oysters, once native to Europe, are now cultivated in Maine. Two types of oysters available in the western U.S. are Pacific oysters and the more rare Olympia oysters. Kumamoto oysters, originally from Japan, are now farmed along the Pacific Northwest coast from California to Washington.
To shuck oysters on the half shell for consumption, insert the blade of an oyster knife is between the two shells of the oyster. The shells are then forced open and separated. The oyster itself must also be freed by severing the membrane with which it clings to the shell.
Oysters on the half shell must be eaten while they are still alive. Once harvested, oysters may be kept alive for up to two weeks with proper storage. Contrary to common belief, oysters are not seasonal, although they are best eaten in the cooler months between September and April, when there is less chance of spoilage. Oysters from unsafe waters may contain harmful bacteria or chemicals and should therefore be eaten with caution.
Each type of oyster has a distinct flavor and may simply be served on the half shell in its own juices. When served with condiments, popular choices include wedges of fresh lemon, a hot chili sauce, or a spicy, ketchup-based cocktail sauce. Oysters on the half shell may also be served with a mignonette sauce made with white wine, vinegar, and shallots. Oysters on the half shell are also popular in sushi bars, where they are accompanied by soy sauce and wasabi.