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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.
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