COLLECTING OYSTER SPAT SERIES

This form of culture was replaced by cupped oyster ( Crassostrea angulata) production in 1950. Spat were cemented individually onto poles, which were hung from frameworks developed over mussel leasing grounds. Growout facilities were developed in shallow waters (3-4 m), then oyster culture increased substantially by transferring spat from traditional spatfall areas (Brittany). On the Mediterranean coast, off-bottom culture was initiated in 1900, using oysters cemented onto steel poles. Coated tiles became the main method of spat collection in France and the Netherlands: spat were removed by hand after 6-10 months, then reared in trays or re-laid in subtidal plots. Then, in 1865, the liming tile technique (roof tiles coated with a mixture of lime and fine sand), and wooden boxes to grow juveniles were developed in south-western France. Mostly in intertidal areas, wooden spat collectors were initially used followed by oyster shell strings and slates. Eventually, the 'leasing ground' system and the development of artificial spat collectors and their systematic use facilitated the development of the sector. Shortage in seed supply prompted the managers to develop cultural practices aimed to sustain a repletion and reseeding programme. During the 18th and 19th centuries, fishing effort led to over-exploitation, failing recruitment, and destruction of European natural beds, which were also affected by extremely cold winters. A decline in activity in salt marshes facilitated oyster culture development by expanding grow-out acreage availability. In the 17th century, oyster spat were collected on rocks, separated from each other and deployed into ponds in salt marshes on the Atlantic coast of France. The Romans built ponds to stock and sort oysters. The flat oyster Ostrea edulis, a native of Europe, has been part of the human diet for many centuries. Oyster hydraulic dredging boat Profile Historical background The flat oyster can grow very large (>20 cm) and become very old (>20 years). edulis occurs from the coast of Norway to waters near Morocco, through the Mediterranean Sea, and into the Black Sea. The hard rough gray shell contains a meat that can vary in color from creamy beige to pale gray, in flavor from salty to bland, and in texture from tender to firm.

COLLECTING OYSTER SPAT SERIES

Shell consist of a series of chalky layers which may include laminar and hollow chambers. The shell is off white, yellowish or cream in colour with light brown or bluish concentric bands on the right valve. A large central muscle serves to close the valve against the pull of the ligament. Valves are held together at their narrow ends by an elastic ligament. Inner surfaces of both valves are smooth and usually pearly, white or bluish-grey, often with darker blue areas. Left shell is deeply concave and fixed to the substratum, the right being flat with rougher edges and sitting inside the left acting as a lid. The two halves (valves) of the shell are different shapes subcircular to circular and inequivalve.

The irregular shell has a distinct hooked beak, patterned with delicate foliation. Ostrea edulis is a bivalve mollusc that has an oval or pear shaped shell with a rough, scaly surface.

Collecting oyster spat