Reproduction and larval development in two Pecten maximus (L.) populations from Brittany

Abstract The exploited bivalve Pecten maximus shows great irregularities in recruitment. This study, realized on two populations, intends to evaluate the influence of the reproductive process on those irregularities. In the bay of St. Brieuc a synchronous maturation of all the individuals results in a massive spawning in the early July when the water temperature reaches 15.5–16°C. Thereafter, secondary spawning periods take place until the end of August. In the bay of Brest, mature individuals are present all year round. The interindividual synchronism is weak and partial spawnings stretch out from May to September. Also some differences on the egg size, the larval life span and the length at metamorphosis were noted. A spreading out of the risks is thus noted for the Brest population where the spawning, fractioned over several months, increase the global chances of success over the year. On the contrary, at St. Brieuc, the success or failure of the main spawning is determinant for recruitment.