Résumé
The Thau lagoon, located at the South of France, provides 10% of the French pacific oyster Crassostrea gigas production (Robert et al., 2013). Despite this intensive shellfish production, the larval recruitment of this species within the Thau lagoon is still misunderstood and spat collection remains highly variable; as a consequence, shellfish farmers rely mostly on hatchery's spat. In 2012, the PRONAMED II project was launched, aiming to improve our understanding of the C. gigas reproductive cycle within Mediterranean lagoons and to explore the feasibility for oyster-spat collecting. In addition to an extensive sampling work encompassing both spatial and temporal features of larval recruitment, we tried to understand the contribution of larval dispersal on recruitment patterns. For this purpose, we developed new approaches using the MARS 3D hydrodynamical model. While most models keep looking at the location of larvae after a simulation duration specified by the user, we propose here a new approach considering the pelagic larval duration and focusing on the duration of the larval competency for settlement. A new index was set up to take into account the binary possibility for the larvae to settle or not during its final pelagic stage, the settlement probability increasing with the amount of larvae passing through a model mesh.