As winter approaches, the larger species of fish--tuna, swordfish, grouper and shark--migrate to the warmth of the Southern Hemisphere. Other finfish head for deeper waters and lie low while the waves crash on the shores.
But the wild waves are just a cover for the greatest treasures of the deep: the mollusk families of clams, mussels, oysters and scallops. Cold winter waters produce the most succulent shellfish, plump from summer and autumn feeding. The cold also helps preserve them after harvesting. In warmer weather, the delicate creatures lose moisture during the trip from ocean floor to fish market. Winter's frigid temperatures protect their beauty.
The hard-shell clam family (Mercenaria mercenaria) of the East Coast, which is sold according to size, includes the young 3-year-old littlenecks, 4-year-old topnecks, 5-year-old cherrystones and the mature quahogs, which are primarily used for chowders. West Coast butter clams, giant geoducks and ore recent transplants, including the Manila clam, are also at their best now.
The blue mussel (Mytilus edulis) , native to the North Atlantic, has also been introduced into West Coast waters to supplement the supply of the native Pacific variety M. Californianus. Mussels begin their lives as free-swimming spats. Eventually they attach themselves to rocks by means of a protein, related to silk, which hardens on contact with water. This attachment, called a byssus or beard, is easily removed from the mussel before serving.
The most important member of the East Coast oyster family is the species Crassostrea Virginica . The oysters are usually marketed according to the location of their breeding and harvesting, such as Bluepoint, Chatham or Malpeque.
Many terrific oysters also come from the Northern Pacific, the native species being Ostrea Lurida, which we know as Olympia, Yaquina or Willapa oysters. The larger Pacific oyster (Crassostrea Gigas) was introduced from Japan, while the flat plate oyster, Ostrea Edulis, is the famous Belon oyster of France.
The scallop is the most revered of the mollusk family for its sweet, delicate meat. Europeans are also fond of the orange-colored "coral" or roe. Unlike clams, mussels and oysters, scallops can swim. They expel water by rapidly opening and closing their shells, and thus they can migrate between feeding and breeding grounds. Because the shells do not close tight, however, they spoil quickly out of water, so they are shucked on the boat or dock and immediately iced to preserve their flavor.
More than 400 varieties of scallop live in the seas, but only half a dozen occur in sufficient quantities to allow commercial harvesting and distribution beyond their native environment.
The bay or cape scallop (Argopecten Irradians) is the most renowned because of its sweet and resilient texture. It is native to the small inlets of the Northeast, with a season from September to April. The demand for this scallop is enormous and the supply is quickly used up. Catch this treasure now or you'll have to wait until next autumn. Select tiny scallops that are creamy in color, but not white.
The Atlantic sea scallop (Placopecten magellanicus) is the most abundant and widely distributed. It is harvested from depths up to 900 feet, and individuals are commonly as large as five inches across the shell. They are delicate in flavor but slightly softer in texture than bay scallops. Select the more translucent ones with a shiny coat.
The Pacific rock scallop (Hinnites giganteus) is quite large and occurs from Baja to Alaska, the better ones coming from the colder northern waters. The weather-vane scallop (Patinopecten Caurinus) is a delicacy from the Gulf of Alaska. The calico (Argopecten gibbus) occurs from Brazil to the Carolinas and the Gulf but is considered the least palatable because it is firmer and less sweet in flavor. Select calicos that are white with a dull coat.
Unscrupulous merchants will sometimes sell calicos as bay scallops. You can tell calicos by their slightly "cooked" appearance--the result of the high temperature steaming required to open their shells. Bays are almost always hand-shucked and remain translucent.
Scallops will absorb water, increasing their weight and diluting their natural flavor. Phosphate washes are used by some harvesters to increase the weight and whiten the color. Avoid dull, white and mushy specimens. The smell should be sweet and briny like the sea--not sour and ammonia- or iodine-scented.
Clean scallops by removing the side membrane or foot, if still attached, which once held the scallop to the shell. This foot is tough and chewy when cooked and distracts from the glorious, resilient scallop texture. Remove any splintered pieces of shell. Wash under running cold water only if dirty--water will diminish the delicate flavor.