Data from: Mobulid rays feed on euphausiids in the Bohol Sea

Mobulid rays have a conservative life history and are caught in direct fisheries and as by-catch. Their subsequent vulnerability to overexploitation has recently been recognized, but fisheries management can be ineffective if it ignores habitat and prey preferences and other trophic interactions of the target species. Here, we assessed the feeding ecology of four mobulids (Manta birostris, Mobula tarapacana, M. japanica, M. thurstoni) in the Bohol Sea, Philippines, using stomach contents analysis of fisheries specimens landed between November and May in 2013–2015. We show that the mobulids feed heavily on euphausiid krill while they are in the area for approximately six months of the year. We found almost no trophic separation among the mobulid species, with Euphausia diomedeae as the major prey item for all species, recorded in 81 of 89 total stomachs (91%). Mobula japanica and M. thurstoni almost exclusively had this krill in their stomach, while M. tarapacana had a squid and fish, and Ma. birostris had myctophid fishes and copepods in their stomachs in addition to E. diomedeae. This krill was larger than prey for other planktivorous elasmobranchs elsewhere and contributed a mean of 61 364 kcal per stomach (±105 032 kcal s.e., range = 0–631 167 kcal). Our results show that vertically migrating mesopelagic species can be an important food resource for large filter feeders living in tropical seas with oligotrophic surface waters. Given the conservative life history of mobulid rays, the identification of common foraging grounds that overlap with fishing activity could be used to inform future fishing effort.

蝠鲼类（mobulid rays）具有保守的生活史特征，既会被直接渔业捕捞，也会作为兼捕渔获物被捕获。其后续面临过度捕捞威胁的脆弱性近来已得到学界认可，但如果渔业管理忽视目标物种的栖息地偏好、猎物选择及其他营养级相互作用，则可能收效甚微。本研究针对菲律宾保和海海域的4种蝠鲼类（分别为双吻前口蝠鲼*Manta birostris*、智利蝠鲼*Mobula tarapacana*、日本蝠鲼*M. japanica*、腾氏蝠鲼*M. thurstoni*），通过分析2013-2015年11月至次年5月间上岸的渔业捕捞样本的胃容物，评估其摄食生态。研究表明，当该类群在该海域停留约半年时间时，会大量摄食磷虾（euphausiid krill）。研究发现，蝠鲼类各物种间几乎不存在营养生态位分化，所有物种的优势猎物均为迪奥梅德磷虾（Euphausia diomedeae），在总计89个胃样本中有81个检出该物种（占比91%）。日本蝠鲼与腾氏蝠鲼的胃容物中几乎仅包含该磷虾物种，而智利蝠鲼的胃中除该磷虾外还检出头足类与鱼类，双吻前口蝠鲼则额外包含灯笼鱼科鱼类与桡足类。该磷虾的体型大于其他海域浮游生物食性板鳃亚纲鱼类（elasmobranchs）的猎物，单个胃容物的平均能量可达61364千卡（标准误±105032千卡，能量范围为0至631167千卡）。本研究结果显示，垂直洄游的中层深海物种可作为栖息于贫营养表层水体热带海域的大型滤食性动物的重要食物资源。鉴于蝠鲼类保守的生活史特征，识别与渔业活动重叠的共同觅食场，可为未来渔业作业规划提供科学参考依据。