Life history, growth, and reproductive biology of four mobulid species in the Bohol Sea, Philippines

This study focuses on female life-history parameters and reproductive cycles for four mobulid rays (Mobula thurstoni, Mo. japanica, Mo. tarapacana, and Manta birostris) caught in a targeted fishery in the Philippines. We collected size and reproductive data from 1,510 specimens (30% of catch) landed in two seasons in 2015 and 2016. Sexual maturity was assessed by visual examination of 1,034 specimens, to determine size-at-maturity and size-at-pregnancy. Females of all species matured at a larger size than males. Pregnancy ogives were estimated for all species except Mo. tarapacana, and shifted to the right of female maturity ogives, suggesting that only a small percentage of the female reproduce upon reaching sexual maturity. We report an aseasonal reproductive cycle at the population level for both Mo. thurstoni and Ma. birostris due to the absence of specific ovulation cycle and the wide size ranges of embryos examined throughout the months. The development of the follicles is not alw...