• Atherina boyeri;
  • lagoon;
  • breeding season;
  • fecundity;
  • egg size;
  • strategy

The breeding season of Atherina boyeri living in the brackish lagoons of Mauguio, Pérols and Méjean (Hérault, southern France) was very protracted (February-September). The peak of the reproductive effort occurred in April, May and June. Larger fishes started spawning earlier, and stopped later, than smaller ones. Batch fecundity varied from 4 to 447 oocytes and was positively related to female length and weight. Monthly mean fecundity increased at the beginning of the breeding season and decreased between June and July. Individual mean oocyte diameter ranged from 1.34 to 1.94 mm and was not related to fish length. Monthly mean oocyte size declined throughout the breeding season as water temperature rose. There was no trade-off between number and egg size. The strategy of these sand smelts seemed well adapted to ensure spawning success without endangering their survival. The highest reproductive effort period occurred in such a way that environmental conditions were suitable to the best survival and growth of hatched larvae. When breeding ceased, fishes, particularly the youngest ones, had enough time to improve their condition before overwintering.