Pacific oyster

The Pacific oyster, Japanese oyster or Miyagi oyster (Crassostrea gigas), is an oyster native to the Pacific coast of Asia. It has become an introduced species in North America, Australia, Europe, and New Zealand.

Etymology

The species name comes from the Latin crass meaning "thick",ostrea meaning "oyster" and gígās meaning "giant".

Description

The shell of Crassostrea gigas varies widely with the environment where it is attached. Its large, rounded, radial folds are often extremely rough and sharp. The two valves of the shell are slightly different in size and shape, the right valve being moderately concave. Shell colour is variable, usually pale white or off-white. Mature specimens can vary from 80 mm to 400 mm long.

Ecology

Habitat

Crassostrea gigas is an estuarine species, but can also be found in intertidal and subtidal zones. They prefer to attach to hard or rocky surfaces in shallow or sheltered waters up to 40 m deep, but have been known to attach to muddy or sandy areas when the preferred habitat is scarce. The Pacific oyster can also be found on the shells of other animals. Larvae often settle on the shell of adults, and great masses of oysters can grow together to form oyster reefs. The optimum salinity for Pacific oysters is between 20 and 35 parts per thousand (ppt), and they can tolerate salinities as high as 38 ppt; at this level, however, reproduction is unlikely to occur. The Pacific oyster is also a very temperature tolerant species, as it can withstand a range from -1.8 to 35°C.

Crassostrea

Crassostrea is a genus of true oysters (family Ostreidae) containing the most important oysters used for food.

Species

Eastern oyster

The eastern oyster (Crassostrea virginica)—also called Wellfleet oyster,Atlantic oyster, Virginia oyster, or American oyster—is a species of true oyster native to the eastern seaboard and Gulf of Mexico coast of North America. It is also farmed in Puget Sound, Washington, where it is known as the Totten Inlet Virginica. Eastern oysters are and have been very popular commercially. Today, less than 1% of the original 17th-century population (when the original colonists arrived) is thought to remain in the Chesapeake Bay and its tributaries, although population estimates from any era are uncertain. The eastern oyster is the state shellfish of Connecticut, its shell is the state shell of Virginia and Mississippi, and its shell in cabochon form is the state gem of Louisiana.

Description

Like all oysters, Crassostrea virginica is a bivalve mollusk with a hard calcium-carbonaceous shell. Its shell provides protection from predation.

This particular type of oyster has an important environmental value. Like all oysters, C. virginica is a filter feeder. They suck in water and filter out the plankton and detritus to swallow, then spit the water back out, thus cleaning the water around them. One oyster can filter more than 50 gallons of water in 24 hours. Eastern oysters also provide a key structural element within their ecosystem, making them a foundation species in many environments, and they serve as ecosystem engineers in western Atlantic estuaries. Similar to coral reefs, oyster beds provide key habitat for a variety of different species by creating hard substrate for attachment and habitation. Oyster beds have an estimated 50 times the surface area of an equally sized flat bottom. The beds also attract a high concentration of larger predators looking for food.

Chesapeake Bay

The Chesapeake Bay (/ˈtʃɛsəpiːk/ CHESS-ə-peek) is an estuary lying inland from the Atlantic Ocean, and surrounded by the North American mainland to the West, and the Delmarva Peninsula to the east. It is the largest such body in the contiguous US. The northern bay is within Maryland, the southern portion within Virginia, and is a very important feature for the ecology and economy of those two states, as well as others. More than 150 major rivers and streams flow into the bay's 64,299-square-mile (166,534 km²) drainage basin, which covers parts of six states (New York, Pennsylvania, Delaware, Maryland, Virginia and West Virginia) plus all of the District of Columbia.

The bay is approximately 200 miles (320 km) long from its northern headwaters in the Susquehanna River to its outlet in the Atlantic Ocean. It is 2.8 miles (4.5 km) wide at its narrowest (between Kent County's Plum Point near Newtown and the Harford County shore near Romney Creek) and 30 miles (48 km) at its widest (just south of the mouth of the Potomac River). Total shoreline including tributaries is 11,684 miles (18,804 km), circumnavigating a surface area of 4,479 square miles (11,601 km²). Average depth is 21 feet (6.4 m), reaching a maximum of 174 feet (53 m). The bay is spanned twice, in Maryland by the Chesapeake Bay Bridge from Sandy Point (near Annapolis) to Kent Island and in Virginia by the Chesapeake Bay Bridge-Tunnel connecting Virginia Beach to Cape Charles. Known for both its beauty and bounty, the bay is becoming "emptier", with fewer crabs, oysters and watermen in recent years. Recent restoration efforts begun in the 1990s have been ongoing and show potential for growth of the native oyster population.

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