Our 12 nurseries then share the micro-spat grown in the micro-nurseries.
In the nursery, the oyster spat is put into mesh baskets, themselves placed in concrete-based ponds. The technique used is a closed-loop system : seawater passes through the mesh baskets, before being returned to the reserve and pumped back to the mesh baskets. The oyster spat is fed a daily diet of phytoplankton (Skeletonema costatum). Some of the seawater is changed every day via the Polder's canals.
The spat is washed regularly in the mesh baskets and sieved every two weeks to make the batches more homogeneous. Different growth rates can be observed within the same spawning, hence it is important to separate the biggest from the smallest to reduce competition: the biggest filter a much greater quantity of phytoplankton to the detriment of the smallest.
The spat increases in size from 1 mm to Size 6 (Size 6 = spat that can be collected on a mesh with squares with sides measuring 6 mm). As they grow, the oysters take up more and more room. As a result, the bigger the spat, the greater the number of mesh baskets required for the same quantity. At this stage, some of our production is sent out to customers, while the remainder is boxed up for intermediate grow-out in intertidal zones in Normandy, Brittany and Jersey.