Everything You Wanted to Know But Were Afraid to Ask Oysters on the Half Shell: Kinds, Qualities, Drinks Kinds of Oysters: What's Your Type? A Natural History of Oysters: They Reproduce How?

Choosing

When choosing oysters at the market, the primary consideration is that they be fresh, they do not smell and if one is open (which it shouldn't be) it should snap shut emphatically once tapped. If an oyster doesn't close immediately, don't buy it. The oysters should be arranged so that they are lying flat, not piled willy-nilly. The shape of the shells will give you a good idea of the amount of meat you are getting. The deeper the cup of the lower shell, the better. The rounder varieties of oysters, such as Belons and Olympias, should be symmetrical. For the more elongated Atlantic and Japanese oysters, look for shells that fan out widely from the hinge, indicating that the oysters have had plenty of room to develop.

When to Buy What

Good oysters of the Atlantic and Japanese varieties are available year-round. Belons and Olympias do, in a way, justify the old rule about not eating oysters in months without the letter "r" in the name, so you are unlikely to find them in markets. This is not because they are dangerous; it is the result of differences in the way they reproduce.

Storing

Do not store the oysters in water. If you do not plan to eat them right away, arrange them flat on a tray, cover them with a damp towel, and store them in the refrigerator. They'll keep this way for one or two days.

Shucking

It can be difficult to shuck an oyster, mostly because both the oyster and the shucking knife require a fair amount of brute strength to master, but the idea is simple. The oyster is held with the deep shell down, to preserve as much of the liquor as possible. Then the knife (which is unlike a kitchen knife, in that it has a blunt tip and a much stiffer blade) is slipped between the shells so that they can be pried open. The muscles attaching the meat to the upper and lower shells are then cut, so that the oyster can be removed with a fork. Some people hold the oyster in the hand while shucking; others set it on a flat surface. Some people approach the task by first cutting through the hinge; others pry it open from the other side. If you want to, you can always have the fish monger do this job for you.

There are easier, tidier methods (which die-hards would call cheating) for opening your oysters, however. Putting the oysters in the freezer for two or three hours, and then allowing them to return to room temperature will cause them to open by themselves, as will placing them in the microwave for about 20 seconds. Both of these methods kill the oysters, so it is important to serve or cook them immediately.