Etude comparative du cycle de reproduction de la palourde Ruditapes decussatus en milieu naturel (sud Tunisie) et contrôlé (écloserie)

A comparative study ofthe reproductive cycle o/'Ruditapes decussatus under natural(South ofTunisia) and con­ trolled conditions (hatchery). The aim of this study was to describe and compare the gametogenic activity of Ruditapes decussatus in situ and in hatchery. Criteria of maturity were characterized and the positive role of conditioning in the suc­ cess of artificial reproduction was underlined. Specimens sampled in the South of Tunisia were conditioned at the experi­ mental station of Monastir (Tunisia). The parameters studied were the variation of the condition index and the frequency distribution of oocyte diameters. Results showed that the reproductive cycle was continuous in situ. Gametogenesis started in January and February. Gonadic activity increased from March to November-December. Spawning events occurred irre­ gularly from June to December. In winter conditioning, mature oocytes were produced from March and spawning began in April. The increase in temperature and food abundance shortened the gametogenesis duration; ripe gametes were produced two months earlier compared to natural environment. In summer conditioning, the reproductive cycle was the same as that in the natural site, maturation and spawning occurred simultaneously.