Data from: Biogeophysical and physiological processes drive movement patterns in a marine predator

Background: Blue sharks (Prionace glauca) are among the most abundant and widely distributed of oceanic elasmobranchs. Millions are taken annually in pelagic longline fisheries and comprise the highest component of auctioned fin weight in the international shark fin trade. Though studies of blue sharks outnumber those of other large pelagic sharks, the species’ complicated and sexually segregated life history still confound current understanding of Atlantic movement patterns. Lack of detailed information regarding movement and vertical behavior continues to limit management efforts that require such data for stock assessment and sustainable catch modeling. Therefore, this study aims to describe behavioral and ecological patterns distinct to aggregating and migrating blue sharks, and compare the findings to existing Atlantic movement models. Results: Data collected from 23 blue sharks instrumented with pop-up satellite archival tags were used in statistical predictive regression models to investigate habitat use during a localized aggregation in the northwest Atlantic, while undergoing seasonal migrations, and with respect to environmental variables. Deployment durations ranged from 4 to 273 days, with sharks inhabiting both productive coastal waters and the open ocean, and exhibiting long-distance seasonal movements exceeding 3700 km. While aggregating on the continental shelf of the northwest Atlantic, blue sharks displayed consistent depth use independent of sex and life stage, and exhibited varied response to environmental (temperature and chlorophyll a) factors. As sharks dispersed from the aggregation site, depth use was influenced by bathymetry, latitude, demography, and presence in the Gulf Stream. Mature females were not observed at the New England tagging site, however, two mature females with recent mating wounds were captured and tagged opportunistically in The Bahamas, one of which migrated to the Mid-Atlantic Ridge. Conclusions: Vertical behaviors displayed by blue sharks varied greatly among locales; depth use off the continental shelf was significantly greater, and individuals exhibited a greater frequency of deep-diving behavior, compared to periods of aggregation on the continental shelf. Sexual segregation was evident, suggesting mature and immature males, and immature females may be subjected to high levels of anthropogenic exploitation in this region during periods of aggregation. Analysis of the spatio-temporal tracks revealed that nine individuals traveled beyond the United States EEZ, including a mature female captured in The Bahamas that migrated to the Mid-Atlantic Ridge. These results reflect and augment existing Atlantic migration models, and highlight the complex, synergistic nature of factors affecting blue shark ecology and the need for a cooperative management approach in the North Atlantic.### 背景： 蓝鲨（Prionace glauca）是海洋板鳃类（elasmobranchs）中数量最多、分布最广的类群之一。每年有数百万条蓝鲨在远洋延绳钓渔业中被捕获，且在国际鱼翅贸易中，其鱼翅重量占拍卖总量的最高比例。尽管针对蓝鲨的研究数量多于其他大型远洋鲨鱼，但该物种复杂且存在性别隔离的生活史，仍让目前对大西洋海域其活动模式的认知存在困惑。目前仍缺乏关于其活动与垂直行为的详细数据，这制约了依赖此类数据开展种群评估与可持续捕捞模型构建的管理工作。因此，本研究旨在描述聚集洄游的蓝鲨所特有的行为与生态模式，并将研究结果与现有的大西洋海域活动模式模型进行对比。 ### 结果： 本研究对23只佩戴弹出式卫星档案标签（pop-up satellite archival tags）的蓝鲨收集的数据，采用统计预测回归模型进行分析，以探究其在西北大西洋局部聚集、季节性洄游期间的栖息地利用情况，以及其与环境变量的关联。标签部署时长为4至273天不等，被标记蓝鲨的栖息范围涵盖高生产力沿岸海域与远洋海域，且其季节性洄游距离超过3700千米。当蓝鲨在西北大西洋大陆架聚集时，其垂直水深利用模式不受性别与生活史阶段的影响，且对环境因子（水温与叶绿素a（chlorophyll a））呈现出差异化响应。当蓝鲨从聚集点扩散后，其水深利用情况则受水深地形、纬度、种群结构以及是否处于湾流（Gulf Stream）海域的影响。研究未在新英格兰标记点发现成熟雌性蓝鲨，但研究人员在巴哈马海域偶然捕获并标记了2只带有近期交配伤痕的成熟雌性个体，其中1只洄游至中大西洋海脊（Mid-Atlantic Ridge）。 ### 结论： 蓝鲨的垂直行为在不同海域存在显著差异：相较于在大陆架聚集的阶段，其在大陆架外海域的水深利用显著更深，且个体的深潜行为频率更高。研究中可见明显的性别隔离现象，这表明在聚集期，成熟雄性、未成熟雄性与未成熟雌性可能在该海域面临高强度的人类开发活动。对时空轨迹的分析显示，有9只蓝鲨的活动范围超出了美国专属经济区（Exclusive Economic Zone, EEZ），其中包括那只在巴哈马海域捕获并洄游至中大西洋海脊的成熟雌性个体。本研究结果印证并补充了现有的大西洋洄游模式模型，同时凸显了影响蓝鲨生态的各类因素间复杂的协同作用，以及北大西洋海域开展合作管理的必要性。