Data from: 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 always synchronous with gestation, supporting the theory of a resting period between pregnancies. Our results show the low reproductive potential of these species and their conservative life history, and suggest that population growth rates previously reported are an overestimate.

本研究聚焦菲律宾海域目标渔业中捕获的4种蝠鲼科（Mobulidae）物种：勃氏蝠鲼（Mobula thurstoni）、日本蝠鲼（Mo. japanica）、塔拉帕卡蝠鲼（Mo. tarapacana）以及双吻前口蝠鲼（Manta birostris）的雌性生活史参数与生殖周期。研究于2015年与2016年的两个渔季中，从上岸渔获内抽取30%的样本（合计1510尾个体），收集了其体型与生殖相关数据。通过对1034尾样本进行目视检查以评估其性成熟状态，进而确定各物种的性成熟体长与妊娠体长。所有受试物种的雌性个体性成熟时的体长均大于雄性个体。除塔拉帕卡蝠鲼（Mo. tarapacana）外，其余物种均估算得到了妊娠累积曲线（pregnancy ogives），该曲线相较于雌性性成熟累积曲线（maturity ogives）整体右移，提示仅少数雌性个体在达到性成熟后即可进行繁殖。研究发现，勃氏蝠鲼（Mo. thurstoni）与双吻前口蝠鲼（Ma. birostris）的种群生殖周期为非季节性，这是因为未观测到特定的排卵周期，且各采样月份内观测到的胚胎体长分布范围较广。卵泡发育并非始终与妊娠进程同步，这一结果佐证了"两次妊娠之间存在休整期"的相关理论。本研究结果表明，此类物种的繁殖潜力偏低且生活史策略偏保守，同时提示此前文献报道的种群增长率存在高估情况。