Crassostrea virginica
eastern oyster
(Also: eastern, american oyster)

Gulf of St. Lawrence to the Gulf of Mexico and the West Indies. It was introduced to San Francisco Bay but did not survive.

Although water temperature affects growth rate, it appears to be irrelevant in site selection. Oysters inhabit areas of fairly constant turbidity and salinity. The oyster is eurytherma,l or able to withstand a wide range of temperatures including freezing temperatures.

The Eastern oyster is relatively large, growing up to 10 cm. in length. It is normally somewhat pear-shaped in outline, but members of this species vary greatly in size and shape. The shell is dirty gray externally and white internally, except for the muscle scar, which is deep purple.

Oysters usually colonize in beds. Competition for space is a most important source of mortality. Uncrowded, oysters can live to be 20 years old. The beds are a permanent social structure unless they are separated physically and forcefully. Otherwise, the oysters will re-congregate if they are capable.

After spawning in early spring, the oyster loses a great deal of weight. This event usually coincides with the spring bloom of phytoplankton, their primary food source. Feeding is dependent upon water temperature; more food is consumed at higher temperatures than at lower.

A major problem caused by the oyster is fouling, or attachment, often to boats.

Oyster cultch or oyster spat is fairly valuable to jewelry trade, though it is rather abundant, due to the large numbers of existing oysters and their relatively high rate of reproductive success. Certain lime or cement coatings are enhaced by use of the cultch. Some Eastern oysters produce pearls as well. Oyster meat is also smoked and canned as a food.

Oyster health is highly contingent upon water quality. Chemical contamination is widespread and detrimental. Extensive efforts are being made in British Columbia to purify water to benefit all aquatic organisms. Toxicity in shellfish can be passed on to consumers, resulting in a condition termed PSP in humans, which is potentially fatal.

Although it is only distantly related to the true pearl oyster (which, in fact, is not an oyster), it can and occasionally does produce pearls. The Eastern oyster can exist in water of extreme variations in turbidity and salinity.