The reproductive cycle of Ruditapes decussatus was studied to assist with understanding the basic
biology of this potential candidate for bivalve aquaculture in Egypt. Clams from three sites along the Egyptian
coast (near Damietta, Ismailia and Alexandria) were examined over a year. Female:male sex ratio was 1:1.02.
There were no significant differences in Mean Gonadic Index (MGI) between males and females or between
different locations confirming a simultaneous life cycle in Egyptian waters. Active gametogenesis in females
began in January-February and in males in December-January. MGI showed one peak of ripe clams (75-100%
ripe) in March for both males and females confirming the beginning of the spawning season, except for Damietta
in which the peak of ripe females was a month later (April, 67% ripe). MGI decreased from April till November
reflecting partial spawning and gamete release. The onset of spawning for both sexes started in April at a
temperature of more than 18°C in the three sites. Spawning peaks were in May in Ismailia males and
simultaneously in June for all females in all sites and males of Alexandria and Damietta . Earlier gametogenesis
and spawning in Ismailia was attributed to higher food availability. From September to November, most females
were classified as either spent or at resting stage while spawning continued till November for males. Size of 50%
maturity was 18.03 and 18.82 mm shell length for females and males, respectively. Clam broodstock (≥ 18 mm
shell length) should be collected no later than February for conditioning in the hatchery to avoid natural
spawning in the field.