The shellfish that Rhode Islanders call a quahog possesses an impressive variety of names, and even the word "quahog" (which comes from the Narragansett Indian name "poquauhock") has an alternate spelling, "quahaug," and a number of pronunciations: KO-hog, KWO-hog, and KWA-hog. The quahog's scientific name, Mercenaria mercenaria, is derived from a Latin word meaning "wages" and was chosen because Indians used quahog shells to make beads that were used as money (called wampum). In much of the United States, quahogs are simply called "hard clams" or "hard-shell clams."

Still other names are based on a quahog's size. Little necks (or "necks") are the smallest legal size, measuring 1-inch thick at the largest thickness; chowders are the largest size; and cherrystones are in between.

In Rhode Island, quahogs grow to legal size in three to four years if conditions are good. A quahog's age can be determined by counting the growth rings on its shell. As quahogs get older, they grow more slowly, so the growth rings get very close together and difficult to count accurately. Researchers estimate that the largest ones (4 inches or more in length) are as much as 40 years old.

Quahogs-like soft-shell clams, oysters, scallops, and mussels-are classified as bivalve mollusks because they have hinged shells made up of two halves, or "valves." Bivalves obtain their food by filter feeding. Water is taken in through a siphon and passed over the gills, which are specially adapted to filter out food (microscopic algae and other small organic particles). The filtered water is then expelled via another siphon. A large clam can filter about a gallon of water in one hour.

Quahogs prefer salinities between 18 and 26 parts per thousand. This is less salty than the open ocean (salinity about 35 parts per thousand), so quahogs are often found in estuaries (such as Narragansett Bay) where the mixing of fresh and salt water provides ideal conditions.

Although quahogs can be found along the North American Atlantic coast from Canada's Gulf of Saint Lawrence to Florida, they are particularly abundant between Cape Cod and New Jersey. Farther north, most waters are too cold for quahogs, restricting them to just a few relatively warm coves; while to the south, quahogs have more predators, such as blue crabs.

Pollution in Narragansett Bay affects the quahog industry because the filter-feeding process concentrates not only food particles but also many pollutants-including disease-causing bacteria and viruses and toxic compounds. Thus, even pollutants that are present only in low levels in the water can accumulate to dangerous levels in filter feeders. RIDEM maintains a list of shellfish areas closed to pollution. It is available at: www.state.ri.us/dem/. For more information about shellfishing regulations, see page 7.

—By Eleanor Ely,
Rhode Island Sea Grant