Monthly samples of the bivalves #Atactodea striata$, #Gafrarium tumidum$ and #Anadara scapha$ were collected over 1 year from the littoral zone on the South-Western coast of New Caledonia. #A. striata$ and #G. tumidum$ were studied by macroscopic examination of gonads and microscopic examination of gamete smears. For #A. scapha$, only microscopic examination was use. #A striata$ and #G. tumidum$ are dioecious, whereas #A. scapha$ is a protandric hermaphrodite. Sexual differentiation begins at a shell lenght of 20 mm for #A. striata$ and #G. tumidum$ aand 22 mm for #A. scapha$. The three species have an extended or continuous breeding period, although, in all three, sexual activity peaks in the hot season. (Résumé d'auteur)
