Reproductive Cycleso Of the Razor Clam Ensis Siliqua and the Clam Venus Striatula off Vilamoura, Southern Portugal

Annual reproductive cycles of two commercially important bivalves, the razor clam Ensis siliqua and the clam Venus striatula were investigated. Specimens of both species were sampled monthly from a site off Vilamoura, south of Portugal, between June 1992 and May 1993. Gonadal development was monitored using standard histological methods. Observed gametogenic progression was categorized by six stages: (0) inactive; (I) early active gametogenesis; (II) late active gametogenesis; (HI) ripe; (IV) partially spawned; and (V) spent. Both males and females showed a synchronism in gonadal development. The gametogenesis in the razor clam began in December and by late April the gonads were characterized morphologically by an abundance of ripe eggs and sperm. Partially spawned individuals were first encountered in May. All were spent by July. The gametogenic activity in V. striatula began in the months of October/November and continued until March. Spawning occurred between April and early August. Both species reached maturity during the first year of life.