A quahog, also called a round clam, hard clam, or chowder clam, is a type of edible clam native to North American shores. Its range spans nearly the entire continent, from Prince Edward Island to the Yucatán Peninsula. The quahog is especially popular in the cuisine of New England and can be served raw, steamed, stuffed, or in soups, stews, or sauces.
The word quahog comes from the Narragansett poquauhock. The clam's scientific name, Mercenaria mercenaria, comes from the Latin for "money," as beads made from the shells were once used among Native Americans as a form of currency called sewant.
Quahogs occur in the greatest numbers between Cape Cod and New Jersey, and they are the official state shell of Rhode Island. In addition to their native habitat, quahogs have been introduced on the North American Pacific coast and in Europe. In some areas, the quahog has been bred to have particular markings on the shell, to distinguish it from clams in other areas.
Different sizes of quahog are given different names in the fish market. The smallest are countnecks, followed by littlenecks and topnecks. Cherrystones are even larger, while the largest are called quahogs or chowder clams. These last two sizes are tougher than the smaller varieties and are used in chowders and stuffed clams, or minced in other dishes. Smaller quahogs may be served raw or, more rarely, steamed with butter.
The quahog population is affected by a little understood parasite known as Quahog Parasite Unknown (QPX). It results in the need to let contaminated runs go fallow for a few years, financially affecting clam farmers. Red tide, an accumulation in clams of a neurotoxin released by algae, is another problem for the clam industry. Because consuming affected clams may be fatal, farmers are extremely careful about red tide and must follow stringent laws. It is safe to purchase and eat clams from a market, but the red tide phenomenon negatively affects the supply of quahogs. As with QPX, red tide requires the affected population of clams to go unfarmed for a significant period of time.