ABSTRACT: The pelagic thresher shark Alopias pelagicus is an understudied elasmobranch harvested in commercial fisheries of the tropical Indo-Pacific. The species is endangered, overexploited throughout much of its range, and has a decreasing population trend. Relatively little is known about its movement ecology, precluding an informed recovery strategy. Here, we report the first results from an individual pelagic thresher shark outfitted with a pop-up satellite archival transmitting (PSAT) tag to assess its movement with respect to the species’ physiology and trophic ecology. A 19 d deployment in the Red Sea revealed that the shark conducted normal diel vertical migration, spending the majority of the day at 200-300 m in the mesopelagic zone and the majority of the night at 50-150 m in the epipelagic zone, with the extent of these movements seemingly not constrained by temperature. In contrast, the depth distribution of the shark relative to the vertical distribution of oxygen suggested that it was avoiding hypoxic conditions below 300 m even though that is where the daytime peak of acoustic backscattering occurs in the Red Sea. Telemetry data also indicated crepuscular and daytime overlap of the shark’s vertical habitat use with distinct scattering layers of small mesopelagic fishes and nighttime overlap with nearly all mesopelagic organisms in the Red Sea as these similarly undergo nightly ascents into epipelagic waters. We identify potential depths and diel periods in which pelagic thresher sharks may be most susceptible to fishery interactions, but more expansive research efforts are needed to inform effective management.

中文翻译：

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浮游性长尾鲨（Alopias pelagicus）的垂直运动：洞察该物种的生理局限性和红海的营养生态

摘要：上层脱粒器鲨鱼Alopias pelagicus是在热带印度洋-太平洋地区的商业渔业中收获不足的under鱼。该物种在其大部分范围内都处于濒危，过度开发状态，种群数量呈下降趋势。对其运动生态学知之甚少，因此排除了明智的恢复策略。在这里，我们报告了装备有弹出式卫星档案传输（PSAT）标签的单个中上层脱粒鲨的第一个结果，以评估其在物种生理和营养生态学方面的运动。在红海中进行的19天部署表明，鲨鱼进行了正常的diel垂直迁移，其中一天的大部分时间都在中上生带中度过200-300 m，而上岸区的大部分时间则花费在50-150 m中，这些运动的程度似乎不受温度的限制。相反，鲨鱼相对于氧气垂直分布的深度分布表明，即使在红海白天发生声学反向散射的高峰期，也避免了300 m以下的低氧条件。遥测数据还表明，鲨鱼垂直栖息地的日光重叠和白天重叠，分别是中小型细小鱼类的分散层，夜间与红海中几乎所有中粗细生物重叠，这是因为它们类似地每晚都向上层水域上升。我们确定了潜在的深度和diel时期，其中中上层清脱器鲨鱼可能最容易受到渔业相互作用的影响，但是需要更广泛的研究工作来指导有效的管理。