Eastern, Pacific or Japanese, European Flat, Olympia, Kumamoto
There are five species of oysters grown commercially in North America. Two are indigenous: The Eastern Crassostrea virginica, which is found from Nova Scotia to Texas, and the tiny Olympia Ostrea lurida, once plentiful from San Francisco to Washington State and now grown only in a few small bays in southern Puget Sound.
The European Flat Ostrea edulis is now raised by half-shell growers on both coasts. The Pacific oyster Crassostrea gigas was brought from Japan to Washington State in the 1920s to replace the Olympia oyster, which was near extinction at the time. The Pacific oyster is now the predominant oyster on the West Coast (and in Europe, since the 1970s).
The small, deep-cupped Kumamoto Crassostrea sikamea was brought to Washington State experimentally in 1947 as a replacement for the cherished but declining Olympia oyster. The Kumamoto is now thought to be extinct in the Kumamoto prefecture in southern Japan where it originated but is now grown by several West Coast half-shell growers and has become the sweetheart of the half-shell trade.
ButΓÇömost people say, amazedΓÇöif there are only five kinds of oysters, what about Malpeque (P.E.I.), Pine Island (NY), Apalachicola (FL), Steamboat Island (WA), FisherΓÇÖs Island (NY), Cotuit (MA), Westcott Flat (WA), Pemaquid (ME), Snow Creek (WA), Hog Island (CA), Quilcene (WA), Holmes Harbor Flat (WA), Kegotauk Salts (VA), and the dozens of others heard of and seen?
According to two thousand years of history and tradition, oysters are named not by their species, but by the bay, town, or region in which they are grown. It is pretty simple, really, once you get the hang of it, and it helps you to pick favorites becauseΓÇöbelieve it or notΓÇöthe flavor of oysters is so dependent on the water they filter through their bodies that MarthaΓÇÖs Vineyard oysters usually taste quite different from Nantucket oysters.
These days oysters are shipped overnight from one coast to the other, making it possible to sometimes find all five species on a restaurant menu or in a fish store. To help clear up any confusion this may cause, many are using Latin names as well as the market names to distinguish one species from another. As for the ΓÇ£RΓÇ¥ months ruleΓÇöthat is, only eat oysters in months which have an ΓÇ£rΓÇ¥ in them, September through AprilΓÇöit remains a good guideline for oyster consumption. Oysters certainly can be eaten in the summer, but the risks from bacteria, which love the warmer water of summer, are greater. In addition, oysters in most areas are spawning, a process called ΓÇ£gameto genesisΓÇ¥ when the stored glycogen, which gives the oyster its sweet taste and firm texture, is given over to gamete production. The texture changes from firm to milky, the taste from sweet to bitter. In the post-spawning recovery period, oysters are thin without sweetness or complexity and taste mostly of brine. The one notable exception to the ΓÇ£RΓÇ¥ month rule is the Kumamoto, which is actually best in summer. They spawn in September or October.
As for the differences among the species:
Eastern: Grown all along the East and Gulf Coasts, this oyster has an oval shell that is sometimes uneven in shape and form. At its best, the Eastern oyster is crisp and briny; it has little complexity but gives a delightful hit of strong, delicious, mineral-laden salt. Usually but not always, it is best from northern waters. Southern oysters tend to be larger, softer, and less flavorful; as a result, it is best to use them for cooking. Some typical names: Wellfleet, Apalachicola, or any other town, island, or body of water with clean growing waters along the East or Gulf Coasts.
Pacific or Japanese: Known for its fluted shell and unusual flavors, this is the oyster, that is most commonly grown on the West Coast and in Western Europe. Once you see it and the Eastern together, you will forever know the difference. The Pacific oysterΓÇÖs taste varies widely but is always distinctive, ranging from cucumber to watermelon but almost always with a fruitiness that is not present in other oysters. Some typical names: Quilcene, Hama-Hama, or any other town, island, or body of water in the Pacific Northwest.
European Flat: The original and, some maintain, ΓÇ£trueΓÇ¥ oyster, grown in Europe, the Northwest, and a few spots in Maine and elsewhere. It has a distinctively round, flat shell (it is most commonly called the flat or, in French, plat). The flavor is decidedly metallicΓÇöyou either love it or hate it, but it is certainly worth trying. These are best enjoyed raw. Some typical names: Snow Creek Flats, Holmes Harbor Flats.
Olympia: The half-dollar-sized oyster, is indigenous to the Northwest and grown only there. Not unlike the flat in flavor. So tiny that eating them is almost a game. Rarely seen outside of the Northwest except in restaurants.
Unquestionably, the best way to eat the finest oysters is raw on the half-shell (see A Note about Shellfish Safety). See below for shucking instructions. Good oysters are expensive, and even those with strong flavors are readily tamed by heat. If you are cooking oysters, buy relatively inexpensive, preshucked oysters, which are usually Eastern oysters from the South. Keep the cooking times as short as possible; as soon as the edges begin to curl, they are done.
Where found: Ubiquitous.
To buy: Oyster beds are certified and inspected; ask to see the tag if you want to be sure of your purchase. Shells should be tightly closed, impossible to budge. In some states, preshucked oysters have a packing or ΓÇ£sell byΓÇ¥ date on the container.
To store: Not in a sealed plastic bag, where they will suffocate. Preferably in a bowl or mesh bag, in the refrigerator, covered lightly with a damp towel. Ice is not necessary; mollusks stay alive for days at 40┬░F.
To clean: Use a stiff brush and scrub the shells thoroughly, in particular the often-encrusted Eastern and European oysters (Pacific oysters tend to be cleaner).
To shuck: Hold the oyster, deep shell down, firmly in a folded kitchen towel over a bowl. Insert the point of an oyster knife, which has a strong pointed blade and protective shield, into the hinge between the shells at the pointed end of the oyster. Turn the knife to pry open and lift the upper shell enough to cut through the hinge muscle. Run the knife point between the shells to open. Once open, scrape the oyster from its shell, but do not remove it. Nestle the shells in some ice or rock salt to keep them from tipping over. Strain any liquor in the bowl and pour it over the oysters. Serve raw on the half-shell with Mignonette Sauce. You can steam, microwave, or grill or roast oysters open. And, if you are careful, you can catch them before they cook through, so they will still retain good flavor and texture.
Best cooking techniques: In stews, chowders, and soups, grilling or broiling, deep-frying.
Substitute: Hard-shell clams.
When is it done? When the edges curl, almost immediately. An overcooked oyster is tough, dry, and rubbery, and it can reach that state in less than 5 minutes.
