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.

本研究聚焦于菲律宾某目标渔业（targeted fishery）中捕获的4种蝠鲼类鳐，涉及物种包括勃氏蝠鲼（Mobula thurstoni）、日本蝠鲼（Mobula japanica）、塔拉帕卡蝠鲼（Mo. tarapacana）以及双吻前口蝠鲼（Manta birostris），旨在阐明其雌性个体的生活史参数（life-history parameters）与繁殖周期（reproductive cycles）。研究团队于2015年与2016年的两个渔季中，从上岸渔获物中抽取1510尾标本（specimens，占总渔获的30%），采集其体型与繁殖相关数据。研究人员通过对1034尾标本进行肉眼检视，评估其性成熟（sexual maturity）状态，以确定性成熟体型与妊娠体型。所有物种的雌性个体均较雄性个体在更大体型时达到性成熟。除Mo. tarapacana外，其余所有物种均拟合了妊娠概率曲线（pregnancy ogives），且该曲线相较于雌性性成熟概率曲线（maturity ogives）右移，提示仅有极小比例的雌性个体在达到性成熟后即可开展繁殖。由于未观测到特定的排卵周期（ovulation cycle），且全年各月份采样的胚胎体型跨度较大，本研究发现勃氏蝠鲼（Mobula thurstoni）与双吻前口蝠鲼（Manta birostris）的种群水平繁殖周期为非季节性（aseasonal reproductive cycle）。卵泡发育并不总是与妊娠（gestation）同步，这支持了"妊娠间隔存在休产期"的理论假说。本研究结果表明，这些物种的繁殖潜能（reproductive potential）较低且生活史策略较为保守，同时提示此前文献报道的种群增长率（population growth rates）存在高估情况。