Analyse des ressources et des caractéristiques individuelles du stock d'oursin Paracentrotus lividus (Lamarck, 1816) du territoire 64

A spatial sampling was carried out for stock assessment of sea urchin P. lividus throughout the Basque coast. A sampling, over the year, was conducted to study the reproductive cycle. This work took place over 2013 and 2014. Reproduction occurs once in spring, between May and August 2014. Among factors affecting the release of eggs, salinity, temperature and hydrodynamics show a significant inter-annual variability in the Basque coast. Thus, the period set in 2014, may fluctuate between years. For the stock, the results showed that 11.85 (+/-0.32) million individuals of harvestable biomass for 724 tones (+/- 137). Stock is spread over the entire surveyed area density and biomass decrease rapidly with depth, individuals are mainly located between 0 and 5 m. Large fluctuations in densities are observed among geomorphological profiles, but on average they are between 3 and 3,8 individuals.m-2. Hydrodynamic conditions particularly energetic over this area are reflected the burrowing behavior pronounced.