Abstract
From February 1990 to July 1992, the reproduction of the blue shark, Prionace glauca, in the south-western equatorial Atlantic Ocean was studied. During this period, 88 females and 82 males were examined. Females were found in 4 different sexual stages: preovulatory (22), pregnant (47), postovulatory (non-pregnant) (7), and subadult (12). Their fork length ranged from 162 to 225cm. Half of the females were in early pregnancy. Embryos in completely different stages of development were found in 4 of them. Oviducal glands of 44 females were examined and in 38 spermatozoa were found. These results indicate that ovulation and fertilization took place from December to July. Most of the males were adult and only 14 specimens seemed to be sexually immature. Many adult males were lacking sperm packs and had a very low volume of seminal fluid, suggesting that they were probably sexually resting. Their fork length ranged from 156 to 228cm.
