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

Abstract

Little 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.

Received June 26, 2013; accepted October 24, 2013

ACKNOWLEDGMENTS

The authors thank members of the Kodiak community who assisted in the collection of Salmon Sharks, including all fish processors and personnel; the NOAA Office of Law Enforcement, including T. Gould; the North Pacific Groundfish Observer program, including R. Swanson; and the Kodiak trawl fleet. We thank D. Horne and his students from Kodiak High School for providing a Salmon Shark and assistance with dissection. We thank J. Brooks on the FV Huntress for the pregnant specimen and pups from his catch on January 2010. We also thank individuals at the Kodiak Laboratory that assisted with dissections: J. Haaga, B. Knoth, C. Long, S. Van Sant, E. Munk, P. Cummiskey, and R. Foy. Further, we thank V. Gallucci (University of Washington), J. Moss (NMFS), L. Hulbert (Alaska Department of Fish and Game), and J. Gasper (NMFS) for providing the samples that were analyzed by the University of Washington. The findings and conclusions in this manuscript are those of the authors and do not necessarily represent the views of NMFS or the Alaska Department of Fish and Game. Reference to trade names does not imply endorsement by the U.S. Government.