It concerns the collect of the larva.

 Oyster biology and reproduction

Systematic

The oyster is a mollusc bivalve ( 2 asymmetrical valves), with lamella branchiae belonging to the filibranchiaes division, to the under-category anysomierous, and to the ostreides family.

Biology

Mature oysters operate a sexual reproduction. The Hollow Oysters Crassostrea gigas are oviparous, thus the ovule fecundation with spermatozoon happens in the water influenced by the current. This is an alternative sexuality. Oysters may enjoy the rule of the male or the female and change their sexuality the year after. Some hermaphrodite may subsist after the growing step but it is rare.

Reproduction

From May-June, mature oysters lose their winter lipidic reserve. They replace it by the “milt”. At maturation gonads become inflated by gametic products. This phenomena is due to the climatic movement, warmer water and high salt rate.

Following an external chock, due generally to the temperature movement, a mollusc lays by emitting a pheromone (hormone), inciting the others oysters to do the same. The male gamete (spermatozoids) and female (ovule) fecundate in the ocean. We do speak about external fecundation.

Larva development

Hatching happens after 24 to 48 hours, the larva begins to secrete its shell. The shell is swimming (pelagic). After 2 or 3 weeks, the foot appears. At this moment the larva begins to seek for a support It is metamorphosing to a “small oyster”, it means a breeding.

Collecting

Around the 14th of July, the oyster farmer put in place the collectors (the supports). In Marennes-Oleron, collectors may be plastic tub, plastic plate threaded and corded, slate pious, pieces of slate threaded and corded, , pleno ( rectangular support full of plastic).

Slate pieces and plastic tub.

The collectors are used as support for those small oysters which metamorphose when they are fixed.

Breeding

18 months later, the breeding has grown up on the collector. It is time to detach the small oysters. This operation is called in French “detroquage” Then oysters are named “grattis”.

It may last from 8 to 12 mouths, 2 techniques are used:

Either the Grattis is sowed directly on the flat fields, and then fished with a fork 12 months later, to put the mollusc in farming. During that period, people have to harrow the oysters to avoid their driving in the mud. Oysters need oxygen.

Flat concession: harrowing and fishing with fork

Or the grattis are put directly in bags on raised fields. Bags are tidied away on iron tables. The bags are regularly tuned over and over and kicked to avoid Oysters to grow in the length way and their sticking on the mesh.

It lasts 8 months. Oysters are put in bags, and let on iron table, and tuned over after each high and low water.

Because they are placed on partial uncovered water area, the adductor mussel has to remain water in the shell. By doing this the mollusc develop capacities to stop the exondation. Thus, the Marennes-Oleron Oysters will never have the need to open the shell. Then, nothing wrong may enter in the oyster. This improve the quality of the product

At the end of the summer or at the beginning of autumn, Oysters are back on earth for refining.

In order to obtain the best Oysters of the market, EARL Boyard practise the refining in Claires. This method give to the Oysters the local special taste and the famous green colour of the region.

 Norms

After filed out, Oyster are put in Claires. Density and timing has to be respected to obtain the Marennes- Oleron trade mark.

Flesh index (flesh quality in comparison with the whole weight of the oyster) is important. This index determines partially the oyster classification. It was created by the interprofessional agreement of the CNC (replacing the ancient AFNOR norm). To have more information regarding this index please refer to “Quels produits choisirs?” .

The main qualities of the refining is  the taste, the texture, and the colour.

The Tartness

The tartness of the Oyster comes from a green pigment called Marennine. The Marennine is produce by a phytoplanktonic alga “The blue Navicule” or Haslea Ostrearia. La marennine settled down on the branchiae when the oyster is underwater.