Information AboutOyster |
| CATEGORIES ABOUT OYSTER | |
| bivalves | |
| edible molluscs | |
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'', Marennes-Oléron]] The name oyster is used for a number of different groups of Mollusk s which grow for the most part in marine or Brackish Water . The shell, usually highly calcified, surrounds a soft body. Gills Filter Plankton from the water, and strong adductor muscles are used to hold the shell closed. Some of these groups are highly prized as Food , both raw and cooked. The oyster is the root of an TRUE OYSTERS The "true oyster" are the members of the family Ostreidae , and this includes the edible oysters, which mainly belong to the Arian genera '' Ostrea '', '' Crassostrea '', '' Ostreola '' or '' Saccostrea ''. Examples are the Edible Oyster, ''Ostrea edulis'', Eastern Oyster ''Crassostrea virginica'', Olympia Oyster ''Ostreola conchaphila'', Pacific Oyster ''Crassostrea gigas'', Sydney Rock Oyster ''Saccostrea glomerata'', and the Wellfleet Oyster (a variety of ''C. virginica''). Physical characteristics
Oyster habitat and lifestyle As a keystone species, oysters provide Habitat for an extensive array of marine life. The native oyster usually inhabits water depths of between 8 and 25 feet. The hard surfaces of oyster shells and the nooks between the shells provide places where a host of small animals can live. Hundreds of animals such as Anemones , Barnacles , and hooked Mussels use oyster reefs as habitat. Many of these animals serve as food for larger animals, including Striped Bass , Black Drum and Croakers . An oyster reef can encompass 50 times the surface area of an equally extensive flat bottom. The oyster contributes to improved water quality through its filter feeding capacity. An oyster's mature shape often depends on the type of bottom to which it is originally attached. It orients itself with its outer, flared shell tilted upward. One valve is cupped and the other is flat. The submerged shell opens periodically to permit the oyster to feed. Oysters usually mature by one year of age. They are protandric, which means that during their first year they spawn as males (releasing sperm into the water). As they grow larger over the next two or three years and develop greater energy reserves, they release eggs, as females. Bay oysters are usually prepared to spawn by the end of June. An increase in water temperature prompts a few initial oysters to spawn. This triggers a spawning 'chain reaction', which clouds the water with millions of eggs and sperm. A single female oyster can produce up to 100 million eggs annually. The eggs become fertilized in the water and develop into larvae, which eventually find suitable sites on which to settle, such as another oyster's shell. Attached oyster larvae are called 'spat'. Spat are oysters 25 mm or less in length. Some oysters in the tropics grow on Mangrove roots and are exposed at low tide making them easy to collect. In Trinidad in the West Indies tourists are often astounded when they are told that "oysters grow on trees." The oyster's greatest predators include crabs, sea birds, sea stars, and humans. Oysters as food Although Jonathan Swift is often quoted as having said, "He was a bold man that first ate an oyster,"''Polite Conversations'', 1738, cited e.g. in 1 , evidence of oyster consumption goes back into prehistory, as evidenced by Oyster Middens found worldwide. Oysters were an important foodstuff in all coastal areas where they could be found, and oyster fisheries were an important industry where they were plentiful. Overfishing and pressure from diseases and pollution have sharply reduced supplies, but they remain a popular treat, celebrated in Oyster Festival s in many cities and towns. Oysters are a favorite among erotic foods and research now shows this shellfish to be a rich source of zinc, one of minerals required for the production of testosterone. Oyster fishing Oysters are fished by simply gathering them from their beds. A variety of means are used. In very shallow waters they can be gathered by hand or with small Rakes . In somewhat deeper water, long-handled rakes or oyster Tongs are used to reach the beds. Patent tongs can be lowered on a line to reach beds which are too deep to reach directly. In all cases the manner of operation is the same: the waterman scrapes together a small pile of oysters, and then collects these by scooping them up with the rake or tongs. In some areas a Dredge is used. This is a toothed bar attached to a chain bag. The dredge is towed through an oyster bed by a boat, picking up those oysters in its path. While dredges collect oysters more quickly, they can be very damaging to the oyster beds, and their use is in general strictly limited. In the state of Maryland , dredging was until 1965 limited to Sailboat s, and even since that date motor power can only be used on certain days of the week. These regulations prompted the development of specialized Sailboat s (the Bugeye and later the Skipjack ) for dredging. Oysters can also be collected by Divers . In any case, when the oysters are collected, they are sorted to eliminate dead shells, unwanted catch, and other debris. Then they are taken to market where they are either canned or sold live. Oysters have been cultured for well over a century. Two methods are commonly used. In both cases oysters are cultivated to the size of "spat", the point at which they attach themselves to a substrate. They may be allowed to mature further to form "seed" oysters. In either case they are then set out to mature. They may be distributed over existing oyster beds and left to mature naturally, to be collected using the methods for fishing wild oysters. Or they may be put in racks or bags and held above the bottom. The oysters are harvested by lifting the bags or rack to the surface and removing mature oysters. The latter method avoids losses to some predators, but is more expensive.2 In many areas non-native oysters have been introduced in attempts to prop up failing harvests of native varieties. For example, the eastern oyster was introduced to California waters in 1875, while the Pacific oyster was introduced there in 1929.3 Proposals for further such introductions remain controversial.
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