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Oyster-Farming, Marennes-Oleron

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The Ostreiculture (Oyster-Farming)

Numerous books and magazines describe the world of the ostreiculture (oyster-farming). It is much more interesting and comes alive when one tries to get a basic understanding of the fundamentals by visiting the production localities and by talking to the oyster producers.

With this in mind, take the small road which runs along the channel of La Cayenne and which joins the river Seudre from Marennes.

The direction of La Cayenne is well indicated from the centre of Marennes.

A museum dedicated to oysters

On the left, about a hundred metres before arriving at the Seudre, you will see a small building, the Le Cayenne restaurant with its sale bench and its Eco-Musée, a museum dedicated to oysters. The visit is free.

All the objects, tools, ustensils and instruments of yesterday and today are there.

There are some curiosities such as old bicycles covered with the shells of oysters which have formed after time spent in the sea, where the oysters collected upon the bicycles.

Panels, classified according to the months of the year, explain clearly everything you need to know to fully appreciate oysters.

Here is what you will learn by visiting the museum and by reading the panels.

The eventful history of Marennes-Oléron oysters

The first oyster parks appeared in 1780.

Wild oysters were taken fully-grown and cultivated for a time in ponds. Until 1868, only the flat oysters were cultivated.

Then, in 1868 a boat "Le Morlaisien" loaded with Portuguese oysters was forced by a storm to take refuge in the estuary of the Gironde.

Given the perishable nature of its load, the maritime authorities gave the order to release it.

The unexpected consequence of this was that the oysters developed in the estuary of the Gironde.

The favourable currents spread the domaine of the Portuguese oysters to the Marennes-Oléron basin.

So, the beautiful flat oysters disappeared.

In 1967, the production of Portuguese oysters decreased. It was then that oysters from Japan and Canada were imported.

From start to finish: the work and the know-how of the oyster producers

The hollow oyster is oviparous and the flat oyster is viviparous. Under the summer sun, the hollow oyster is full of its ‘milk’ and will go and spread its reproductive cells in the water.

The union of one male cell and of one female cell forms a tiny egg which drifts according to the currents. Every female oyster gives birth to more than a million eggs. So that the breeding is successful, several conditions must be observed ; favourable climatic conditions, a good water temperature, 21 degrees and the necessity of rivers nearby to supply water which is not too salty.

After about twenty days, invisible eggs settle on solid and clean supports. The first task of the oyster producer is to supply these supports which are called "collectors" and are made from oyster shells, scallop shells, slates, iron, tiles and plastic tubes. The collectors are installed as the larvae try to settle by the end of July.

Covered with seed oysters called "naissains" in summer, the collectors stay in place until the next spring. It is not possible at this time to separate the fragile shells from the collectors but it is necessary to make room for the ‘naissains’. This is the clarification.

After 18 months of growth on the collectors, the oysters cover them completely. The main work from January until May is the ‘détroquage’ operation which consists of separating the young oysters from the collectors.

As the oysters are returned into the sea, they will grow by two methods. The first is the flat method, oysters are spread out over the ground. They are regularly scratched and harrowed so that they do not go out of shape. The second method is the culture in pockets or in pots. Pockets or pots are put on iron tables 50 cm high and they are turned every two months so that oysters are very round and hollow. An oyster from birth to the time of eating is manipulated about 150 times.

The maturing in "claires"

The oysters are then matured in the "claires". The "claires" are ponds dug in mud or clay which is waterproof. The water supply of the ‘claires’ is ensured by channels which open out on to the sea. Every spring, the ‘claires’ are emptied and left to lie fallow.

Every four or five years, they are dug out again. In the "claires" the blue navicule grows. It is a unicellular algae and it is the pigment from this which is responsible for turning the oysters green.

In the "claires", the blue navicule is absorbed and filtered by the oyster which retains this pigment. This retention of the pigment is unpredictable. The maturing in "claires" is specific to Marennes-Oléron. The basin of Marennes-Oléron provides 80 % of the production of "claires" oysters in France.

An oyster filters two litres of water per hour and feeds on live plankton. Oysters have many enemies. They can attack it whatever its age. The mussel, the seed of mussel which sticks on the oyster and suffocates it, the starfish which throws its stomach in the shell of the oyster and digests it, the winkle driller, the ray, the daurade, the crab.

In readiness for despatch, oysters are fished up in the ‘claires’ and put into cement ponds called ‘dégorgeoirs’ from which the water overflows so that the mud and the sand is filtered from the water. Then the oysters are packed and despatched all over France.

Fifty to sixty thousand tons of oysters are delivered for the Christmas and New year period, more than half the annual production. Marennes-Oléron provides 50 % of the French production of oysters.

Notes