clam shell

How does a clam shell grow?

A thin tissue that adheres to the inner surfaces of the shell, called the mantle, and a thickened rim of muscular tissue at the mantle edge deposit new shell material at the shell edge. Rings on the shell indicate how many years old a clam may be.

How do clams establish themselves on the sea bottom?

clams showing foot

Certain kinds of clams, in early stages of life possess a gland that produces a thread-like material (byssus) that serves to anchor them to grains of sand or rocks. Other types of clams lack a byssal gland and use the foot to burrow into the seabed. As the clam grows, its wedge-shaped foot, which expands and contracts as it moves, becomes more important as a burrowing tool.

How do clams reproduce?

Eggs and sperm are released into the water seasonally, generally in mid-summer when water is warm and planktonic food is abundant. After fertilization of an egg, cellular division produces larvae and eventually tiny clams that settle to the bottom. In a few species, the final stage is completed within the mantle cavity of the parent.

Which of the clam species is of greatest commercial importance to the United States, where is it fished, and what quantities are landed?

surf clam

The oceanic surf clam is the most important commercial species. The largest clam of the U.S. east coast, it sometimes reaches a shell length of more than eight inches. Landings of surf clams in New Jersey and Virginia account for about half the total U.S. annual landings of all clam species. The surf-clam catch in recent years--in shucked meats-- ranged from about 41 to 63 million pounds.

How are soft-shell clams harvested?

They are dug from the intertidal flats of bays and estuaries at low tide in New England, using a short-handled fork to obtain clams living in burrows six to ten inches below the surface. In Chesapeake Bay, because the beds are mostly subtidal, a hydraulic dredge washes clams from the bottom and onto an endless belt that conveys the clams to the dredge boat.

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(File Modified Jun. 16 2011)