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，既会被针对性渔业捕捞，也会作为兼捕渔获物被捕获。这类物种极易因过度开发而受影响的脆弱性已于近期得到学界认可，但倘若渔业管理忽视目标物种的栖息地偏好、猎物选择以及其他营养级互作关系，那么管理措施往往难以奏效。本研究以菲律宾保和海海域2013-2015年11月至5月间上岸的渔业捕捞样本为研究对象，通过胃含物分析方法，评估了4种蝠鲼类的摄食生态，分别为双吻前口蝠鲼（Manta birostris）、智利蝠鲼（Mobula tarapacana）、日本蝠鲼（M. japanica）与腾氏蝠鲼（M. thurstoni）。研究结果显示，当这类蝠鲼在该海域停留约半年期间，其主要食物为磷虾类（euphausiid krill）。本研究发现，各蝠鲼物种间几乎不存在营养生态位分化，所有物种的核心猎物均为迪奥玛德磷虾（Euphausia diomedeae），该猎物在总计89个胃含物样本中的检出率达91%（共81个样本）。其中，日本蝠鲼与腾氏蝠鲼的胃含物中几乎仅含有该种磷虾；智利蝠鲼的胃内除该磷虾外，还包含头足类与鱼类；双吻前口蝠鲼则额外摄食灯笼鱼科鱼类与桡足类。该种磷虾的体型大于其他海域中滤食性板鳃亚纲物种（planktivorous elasmobranchs）的猎物，单胃含物中该磷虾的平均能量约为61364千卡（标准误±105032千卡，能量范围为0至631167千卡）。本研究结果表明，垂直洄游中层大洋物种（vertically migrating mesopelagic species）可作为表层水体贫营养化热带海域中大型滤食性生物的重要食物来源。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，可为未来渔业作业强度的管控提供科学依据。