Quahogs, or hard-shell clams, are bivalve shellfish that inhabit the mud flats of Narragansett Bay.  Quahogs are found along the temperate eastern seaboard from Canada to Florida.  Populations are most concentrated in estuaries between Cape Cod and New Jersey where the salinity is less than that of the open ocean.

Quahogs do not remain fixed for life in one spot; they move through the mud using a muscular foot.  With two short siphons, the quahog filters water in and out of its shell, absorbing plankton, bacteria, and oxygen.  Quahogs are extremely efficient filter feeders, and large quahogs can filter about a gallon of water per hour.

Common predators include sea stars, whelks, crabs, snails, birds, some fish, and humans.  The entire body of the quahog is edible, not just the large adductor muscle that is also found in larger species of clams.  Empty shells with a small hole the size of a pencil point are evidence of consumption by moon snails, dog whelks, or oyster drills.

Quahogs are prized as a human food and constitute one of the Bay's most important fisheries.  Unfortunately, human activity threatens the survival of this species.  Since quahogs are filter feeders, they can absorb bacteria and viruses in polluted waters.  Although low levels of pollutants do not harm the clams, eating polluted clams can make people sick.  However, if pollution in the water stops, the quahog can clean itself simply through its regular filtering action.  The importance of clean estuarine water is beneficial not only to quahogs, but also to the public that depends on them as a food source.  Shellfish are often used as an indicator of Bay health by measuring the pollutant levels of animals in a specific area.

Narragansett Bay once supplied 25 percent of the nation's supply of hard-shell clams.  Due to pollution caused primarily by sewer overflows and storm water runoff, about 60 percent of the Bay's shellfish beds are closed permanently or on a conditional basis.  Conditional closures are determined by the amount of rainfall that occurs over the course of time.

The name "quahog" comes from the Indian name "poquahock," meaning horse fish.  The Latin name Mercenaria mercenaria is derived from a word that means wages and was given to the quahog due to the Native American use of its purple inner shell, or "wampum," as money and jewelry.