Oyster Reproduction in Hatchery

The reproduction of our oysters takes place in a controlled environment within our oyster hatchery located in Vendée. This nursery allows larvae to develop in a healthy environment free from predators. The seawater used is filtered and purified.

Within the hatchery, three main missions capture the attention of the entire team: the maturation of broodstock, the production of phytoplankton, and larval rearing.

Maturation of broodstock

The broodstock (male and female parent oysters) are selected based on their origin, resistance, appearance, organoleptic qualities, growth, etc.

Following this selection, these adult oysters are carefully cleaned and placed in rearing tanks on a bi-monthly basis, from November to July. This time lag allows for the preparation of mature oysters from January to September. By adjusting the temperature and quantity of food, it is possible to achieve multiple spawns throughout the year.

Warm temperatures advance maturity for the first spawns, while cold temperatures delay the maturation process until early autumn. All batches are monitored and undergo regular health checks to verify their condition. Oysters are cleaned and fed daily with two species of phytoplankton (microalgae).

Phytoplankton Culture

Thanks to the supply of groundwater (aquifer of saltwater), naturally rich in trace elements, we cultivate two species of phytoplankton: Skeletonema costatum and Tisochrysis Lutea. Distributed to feed both broodstock and larvae, this phytoplankton, also known as microalgae feed, can be produced either indoors in illuminated and air-conditioned rooms, or outdoors in basins illuminated by daylight.

These productions are based on a sequential mode: every day, a small volume of culture, called inoculum, is diluted in a larger volume of groundwater. After a few days, the algal cells have multiplied, and the operation is repeated until a concentrated culture volume is obtained, sufficient to feed the hatcheries.

Larval Rearing

Spawning and Fertilization

Spawning can be achieved either by thermal shock or by scarification. In the first case, mature broodstock are individually placed in small containers and undergo temperature variations, allowing the spontaneous release of gametes by the broodstock. In the second case, gametes (sperm and eggs) are collected by lacerating the gonad (using a scalpel). Individuals are then sexed by microscopic observations, and females are separated from males.

During a diploid spawn, the eggs are mixed with sperm from diploid male oysters. In the case of a triploid spawn (infertile oysters), the eggs are crossed with sperm from tetraploid males, raised within our R&D (Research & Development) facilities.

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Breeding

24 hours after fertilization, the larvae transition from the trochophore stage to the "D" larval stage (shaped like the letter D). The produced larvae are then raised for about twenty days. The larvae are regularly collected on sieves to ensure batch homogeneity and check their growth. The water is then renewed, and feeding is done daily with the various species of phytoplankton mentioned earlier. When they reach a size of 300 microns, the larvae transition from the veliger stage to the pediveliger stage by developing a foot that allows them to attach. They are said to be competent for metamorphosis, signaling the fixation phase.