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Crassostrea virginica:   (click for more)

Crassostrea virginica:   (click for more)

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FAO Names
En - American cupped oyster, Fr - Huître creuse américaine, Sp - Ostión virgínico.
3Alpha Code: OYA     Taxonomic Code: 3160700803
Diagnostic Features
Shell solid, inequivalve left (lower) valve convex, right (upper) valve tending to be flat, though often bent sitting within the left; inequilateral, beaks and umbones not prominent, tending to be broadly oval in outline but often distorted. Ligament internal, attached to a central triangular pit, with lateral extensions. Sculpture of concentric ridges and lines with a few irregular radiating ribs on the left valve which do not normally meet or indent the margin. Hinge line without teeth in the adult. Shell margins smooth.  Colour white, dirty white or brown, sometimes with dark purple markings. Periostracum thin, dark brown; interior of shell white; adductor muscle scar near the posterior margin, a deep purple or red-brown. 
Geographical Distribution

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Western Atlantic Ocean from the Gulf of Mexico and Panama to South Maine, and in the Gulf of St. Lawrence. Imported in Europe (British Islands to to Bay of Biscay) prior to 1939, but the colonies seem to have some difficulties in proliferating. Caught occasionally, with bottom trawls and dredges, in the Adriatic Sea (Mediterranean Sea).
Habitat and Biology
Sessile (cemented to the substrate on its left valve).Oysters favor estuaries and sounds with salinities between 5 and 30% and are intolerant of prolonged exposure to fresh water or marine salinities.  Filter feeder.Also they are found in shallow areas of tidal to subtidal zones (between 0,5-75 meters),prefer a firm substrate (pilings, hard rock bottoms, and substrates firmed with the oyster shells of previous generations). The American oyster is an epibenthicsuspension feeder, ingesting a variety of algae, bacteria, and small detrital particles. Fecal and pseudofecal material is important in sediment production and deposition, providing sites for remineralizing bacterial action, and as food source for deposit feeders.Swimming larvae have positive phototaxis, which becomes negative with increased temperature.
Size
Measuring to 25 cm cm from hinge-line to the opposite margin; common 8-18 cm.
Interest to Fisheries
American oysters are prominent members of the benthic community in Chesapeake Bay (USA) and contribute substantially to the economy of the region. Oysters have recently experienced severe declines in abundance. Intense fishing pressure, loss of habitat, and water quality degradation have been blamed for declines in the abundance of this species. Its meat is not highly sought after by European consumers. Resource very important in Gulf of Mexico (Tamaulipas, Veracruz and Tabasco). The total catch reported for this species to FAO for 1999 was 132 207 t. The countries with the largest catches were USA (89 714 t) and Mexico (39 268 t).
Marketed fresh.
Local Names
English : American oyster ,  Blue points ,  Blue point oyster ,  Common oyster ,  Eastern oyster .
French : Huitre ,  Huitre creuse americaine .
German : Amerikanische auster .
Italian : Ostrica .
Portuguese : Ostra .
Spanish : Ostión ,  Ostión americano ,  Ostión de placer ,  Ostión de manglar ,  Ostra virgínica .
Remarks
Many enemies, diseases, and other calamities afflict this bivalve. It is preyed upon by sea stars, drills, crabs, flatworms, fishes (such as drums and rays), oyster-catchers, scoters, and other sea ducks as well as man. Sponges, boring clams, mud worms, and crabs also harm oysters. Various protozoans and microbes cause disease and many other species compete for space.
Bibliography
Poppe, G.T. & Y. Goto. - 1993European Seashells.Verlag Christa Hemmen, darmstadt, Germany, vol. II: 221 pp.
Poutiers, J.M.- 1987 Ostreidae. In: W. Fischer; M.-L. Bauchot (eds.) Fiches FAO d'Identification des espèces pour les besoins de la pêche. (Révision 1). Méditerranée et mer Noire. Zone de Pêche 37. Vol. I. Végétaux et Invertébres. Rome, FAO, 447-452.
Stanley, J. & M. Sellers - 1986Species Profiles: Life Histories and Environmental Requirements of Coastal Fishes and Invertebrates (Gulf of Mexico), American oyster. U.S. Fish and Wildlife Service Biol. Rep. 82 (11.64). 25 pp.
Tebble, N. - 1966British Bivalve Seashells. A Handbook for Identification, London Trusties of the British Nuseum (Natural History): 212 pp.
Turgeon, D.D., A.E. Bogan, E.V. Coan, W.K. Emerson, W.G. Lyons, W.L. Pratt, C.F.E. Roper, A. Scheltema, F.G. Thompson & J.D. Williams - 1988Common and scientific names of aquatic invertebrates from the United States and Canada: mollusks.
Vera, J. - 1992 Diccionario multilingüe de especies marinas para el mundo hispano.Ministerio de Agricultura, Pesca y Alimentación. Secretaria General Técnica.  1282 pp.
 
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