Oysters growing : present oyster farming, problems and futur.

General information on oyster farming

Formerly, farming was limited to the looting of the natural benches. Romans were very fond of oysters, as we can find some oyster shell on certain archaeological sites (see history of oyster).
Culture des huîtres au début du siècle Nowadays, oyster farming is a rather special job which has many characteristics. There are a lot of different ways to make oyster.
In France, there are four major methods of production :

Suspended : this method can be used everywhere where there is no tide.
In deep water
On the ground
Elevated farming

Marennes-Oléron farms

History of the Marennes-Oléron farms

Edulis, the flat oyster, is the most ancient cultivated oyster. It still remains but a disease, which kills it in its third year, limits its breeding and thus its sale. It has been replaced by two other species: Crassostrea angulata and Crassostrea gigas.
History of angulata at Marennes-Oléron :
Everything started in 1868 with the Portuguese oyster. That year, a boat, the Morlaisien, was forced to take refuge in the Gironde estuary. From this ship, rotting Portuguese oysters were released in the Gironde and they reproduced and flourished year by year. Seed oysters (small oysters not stuck yet) gradually arrived in the Marenne basin by the north. Angulata could then be farmed and this new specie replaced slowly eludis. This farming lasted until 1970, when the Portuguese oyster was finally struck out by epizooty which destroyed the whole of the oyster farms on the French Atlantic coast.
This story is also told to you in this other page (in french).
The arrival of the gigas :
After this disaster for ostreiculture, we have decided to introduce massively, for an intensive breeding, other specie which is resistant to the disease : Crassostrea gigas, which is still farmed in Marennes Oléron. For this, mothers were brought from Canada and seed oysters were stocked on shells from Japan. Like this, in a few years, the basin's oyster population was replaced.
See the page of short stories for more details.

The various stages before the sale

Collecting : This consists in collecting the seed oyster on wooden, slate, iron or plastic collectors. The oysters may remain on the collectors for 8, 18 or 30 months. The collectors may have various forms and be manufactured out of various materials.

Les collecteurs peuvent être de différentes formes et fabriqués avec plusieurs matériaux.

Flat farming : It is a possible second stage developing for small oysters. They are simply put on the ground, then regularly moved in order to give them a better form and to limit the silting. This solution is less used because of the « bigornaux perceurs » and the feeble production.

Farming in pockets :
We can choose to lock up oysters in plastic pockets on iron tables. The pocket farming makes it possible to obtain better quality oysters. Moreover, we have a good production, because losses are limited.

Refining : This consists in putting oysters in basins (clear water) in order to give them a better taste and to harden them.
Selling : It happens generally from September to October, before the chrismas holydays, period during which 50% of the national production is sold.

Encountered problems

Environmental problems

laveurs de caoutchouc pour éliminer la vase

As we have showed it in the biotope section , this is essential for good oyster farming. It happens sometimes that strong winds, or even storms devastate the farms in sea. This is how some areas have been completely (100%) devastated during the 1999 Christmas storm. And even without taking such spectacular examples, simple current changes may cause serious damages to the oyster farms. We have already seen some sand benches recovering some farms. But the more often, it is only mud banks that recover these farms (also alluvia or finer mud), against what washers (rubber belts stirred up by the currents) are installed in the farms.
Oyster farming is based on a fragile biotope. And the smallest unconsidered action (or even natural ones) can damage it durably.

Competitors

The development of alternative cultures, like for example mussel, caused a lot of harmful effects to certain oyster basins. Thus, in Marennes-Oléron, there is each year more and more seed mussel, which are really invading everywhere. Their elimination is rather expensive. And, knowing that a mussel filters approximately four liters of water per hour, we understand that this way it causes a lack of nutrient for oysters.

We should add the comment that when there is a seed oyster production, the oyster becomes for the oyster farmer, a real adversary. Indeed, in order to obtain a suitable product, it is necessary to remove (« détroquer ») all the small oysters who are fixed on the big ones. These parasite oysters are called « gallies (in french)».

Predation

If there is a real threat which erases all the others in oyster farming, it is surely the winkle driller. This animal eats the oyster (before the consumer) by digging a small circular hole in its shell. Then, it aspirates the oyster with a snout. This animal was marginal until the apparition, recently, of a new and harsher specie (which is able to live longer in aerial places). It has become a real threat for the ground farming. To make everything worse, the winkle driller doesn't seem to have a natural predator which could effectively limit its expansion.
To get rid of this plague, in that matter, the authorities simply recommended the collecting. To encourage this practice, the collected winkle drillers are paid 1 euro per kilo. Because of the speed of reproduction of this specie and the difficulty of collecting it, it wasn't possible to obtain significant improvements.
Other methods are being tested. The installation of bottle caps to the legs of the tables seem to be rather effective for this type of culture.

The starfish is another predator of the oyster, it is rather feared in the deep-water flat cultures, but today it is in regression in Marennes-Oléron.

Epizooties

As with the animals, epizooties may appear in a marine environment. Because of this, the oyster farmers had to cash out between 1970 an 1973. See higher
Other epizooties appeared in America with another specie : Crassostrea virginica. This epizooty was less harsh than with C. angulata but it still caused important losses before the specie becomes resistent to it.

Triploid oysters

S'il est une grande nouveauté pour l'ostréiculture, c'est bien l'huître triploïde. Son nom provient de ce qu'elles possèdent des triplets de chromosomes à la place des doublets habituels. Elles sont obtenues en écloseries à partir de géniteurs tétraploïdes (chromosomes par lot de 4) et diploïdes (paires de chromosomes). Les huîtres obtenues sont stériles.
La particularité des huîtres triploïdes est qu'elles ne fabriquent pas de gamètes avant l'été. Sans le souci de la reproduction, elles poussent plus vite. Elles sont de plus toujours grasses et atteignent une taille plus importante pour une même période d'élevage car elles ne dépensent pas d'énergie pour la reproduction. Certains consommateurs leur trouvent un goût sucré, différents des huîtres normales. Vous les trouverez chez les commerçants sous le nom d'huîtres des quatre saisons.
Elles ne font pas pour autant l'unanimité parmi les éleveurs, certains s'opposent en effet à un élevage contre nature. On est en effet en droit de se demander quels sont les apports pour la profession d'une telle huître, à l'origine mal comprise par les consommateurs, et assimilée (à tord mais c'est discutable) à un OGM. À ce déficit d'image, il faut ajouter que l'utilisation des huîtres triploïdes rend les éleveurs dépendants des écloseries qui peuvent alors développer un monopole sur le naissain. La richesse de la reproduction naturelle est ignorée en même tant que l'image de l'huître comme pur produit de la nature.
Et que dire des manipulations qui aboutissent à la fabrication des triploides, si ce n'est se demander si le jeu en vaut bien la chandelle. Il ne faut pas oublier que la prospérité de l'ostréiculture provient de la réputation de l'huître d'être un produit naturel et bienfaisant. Que ferons les ostréiculeurs si un média influent s'empare de ce sujet épineux peu avant les fêtes de noël ? L'avertissement est lancé ...