Notes on the Reproductive Biology of Female Salmon Sharks in the Eastern North Pacific Ocean

Abstract

AbstractLittle is known about the reproductive biology of the Salmon Shark Lamna ditropis from the eastern North Pacific Ocean. Female Salmon Shark specimens were collected from Alaskan waters in the summer, autumn, and winter to examine reproductive seasonality, the reproductive interval, fecundity, and embryonic development. Female Salmon Sharks were found to ovulate during the autumn months of September and October, and those captured in July were either in a resting or postpartum state, indicating a short gestation time of 9–10 months. The presence of two mature reproductive states in both the summer and autumn months indicates a biennial reproductive cycle and a resting period of at least 14 months between parturition and ovulation. This study found mean fecundity was 3.88 pups per litter (n = 8; SE = 0.13), with the majority of pregnant Salmon Sharks having a fecundity of four sharks per litter. These results provide new information on the reproductive biology of Salmon Sharks and will aid in the development of stock assessments for this species.