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hour through its body cavity, depending on its size, sea temperature and other environmental and biology factors. Some microscopic algae produce toxins which
accumulate in the flesh of mussel, oysters and clams. Shellfish or oysters containing the toxin can induce paralytic shellfish poisoning PSP in human who
eat them Spencer, 1990. 6. Predator and disease
Unprotected oysters and other small bivalves are eaten by various predators, especially drills, starfishes, crabs, fishes and to a lesser extent, by birds
Spencer, 1990. Introduction of Pacific oysters is not thought to have brought pathogens with them that have resulted to post-spawning physiological stress in
warm water when oyster are densely crowded. However, their transport to some countries for direct relaying in the sea has been inadvertently accompanied by a
number of pests and parasites including the Japanese oyster drill, Ocenebrillus inornatus, the oyster flatworm, Pseudostylochus ostreophagus, and copepod
parasite, Mytilicola orientalis. Bacterially related diseases of larvae and early juveniles are not uncommon in hatcheries and are most frequently attributed to
Vibrio spp FAO, 2009.
2.3 Oyster Culture in the Quiberon Bay
The French coastline, which is around 5500 km long, provide favorable environments for mollusk development, particularly oyster which have always
been appreciated by the French. The coast of Brittany is highly varied with numerous bays and estuaries that favour cupped oyster culture. Such as in the Bay
of Quiberon, there is large-scale development of cupped oyster cultivation on the bottom in deep water Buestel et al., 2007.
During 2000s, the production of oyster decreased dramatically. There are some hypotheses about the cause of oyster mortality, it based on disease
OsHV1, predators gastropods, starfishes and gilt head bream and effect of sediments Personal communication CRC and Ifremer, 2010.
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2.4 Economic value of oyster culture
Oyster farming is an aquaculture mariculture practice in which oysters are raised for human consumption. Oyster habitat quality is affected by number of
physical factors, such as water depth, dissolved oxygen, salinity, proximity to the other reefs and biological variables, such as the presence of living oysters on the
reef Henderson and Oneil, 2003. According to FAO 2011 the French aquaculture industry is an old and
established sector, one of the first to develop among the EU countries; 243 907 tonnes were produced in 2004 placing it as the second highest producer in terms
of volume in Europe. Marine production is dominated by molluscs; mainly oyster with 106 750 tonnes and mussels with 74 100 tonnes generating a gross income of
about €600 million produced by the work of 20 000 people in 3 700 farms. Freshwater production is concentrated on trout with 36 611 tonnes produced by
500 farms, most of which produce less than 200 tonnesyear each. The market for shellfish is essentially domestic; Pacific oysters are sold
mainly on the French market but also in Italy 4 000 tonnes, Belgium 700 tonnes and Germany 400 tonnes. France also imports in 2004 oysters from
Ireland 1 600 tonnes, Great Britain 400 tonnes and Spain 300 tonnes. Consumption of oysters is mainly seasonal, with 70 percent of the yearly
production marketed between November and January. The positive trade balance for shellfish produced in France about €12 million, Frances trade balance for
mussels meanwhile is negative with a net import worth about €60 million due to a large volume of imported product from Netherlands 17 100 tonnes, Ireland 13
000 tonnes, Spain 7 500 tonnes as well as other European countries. The main export markets are Spain 2 500 tonnes, Germany 500 tonnes and Italy 400
tonnes. These small scale industry activities contributes largely to France economy.
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2.5 Bibliographical Synthesis of Biological Features of The Major Oyster Predators
