Mercenaria mercenaria and sediment samples were collected from 3 locations in Narragansett Bay: Greenwich Cove, Greenwich Bay, and the West Passage. Greenwich Cove has been closed to shellfishing for several decades. Average density of quahogs in the cove was 190/m super(2), ranging from 32 m super(2)-500/m super(2) in 30 quadrats. Average valve length of quahogs in Greenwich Cove was 62 mm. Average density in Greenwich Bay was 78/m super(2), ranging from 8/m super(2)-184/m super(2). Average valve length was 31 mm. There was a slightly higher content of very fine-grained sands, silts, and clays in the Greenwich Cove sediments. Average Mercenaria) density at another closed site on the West Passage was 46/m super(2) with an average valve length of 61 mm. Quahogs in the bay were 12 yr of age or less. Ages were greater in the closed areas and exceeded 25 years in the largest individuals. The von Bertalanffy growth equation yielded asymptotic valve length maxima suggesting density-dependent stunting in the cove. Active fishing tends to remove adults from the population and enhance either the set or survival of juveniles. Possible mechanisms for increasing the juvenile density include removal of competing adults and sediment disturbance/turnover due to fishing methods.