Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, Plymouth, United Kingdom.
PLoS One. 2012;7(2):e32374. doi: 10.1371/journal.pone.0032374. Epub 2012 Feb 29.
Dramatic population declines among species of pelagic shark as a result of overfishing have been reported, with some species now at a fraction of their historical biomass. Advanced telemetry techniques enable tracking of spatial dynamics and behaviour, providing fundamental information on habitat preferences of threatened species to aid conservation. We tracked movements of the highest pelagic fisheries by-catch species, the blue shark Prionace glauca, in the North-east Atlantic using pop-off satellite-linked archival tags to determine the degree of space use linked to habitat and to examine vertical niche. Overall, blue sharks moved south-west of tagging sites (English Channel; southern Portugal), exhibiting pronounced site fidelity correlated with localized productive frontal areas, with estimated space-use patterns being significantly different from that of random walks. Tracked female sharks displayed behavioural variability in diel depth preferences, both within and between individuals. Diel depth use ranged from normal DVM (nDVM; dawn descent, dusk ascent), to reverse DVM (rDVM; dawn ascent, dusk descent), to behavioural patterns where no diel differences were apparent. Results showed that blue sharks occupy some of the most productive marine zones for extended periods and structure diel activity patterns across multiple spatio-temporal scales in response to particular habitat types. In so doing, sharks occupied an extraordinarily broad vertical depth range for their size (1.0-2.0 m fork length), from the surface into the bathypelagic realm (max. dive depth, 1160 m). The space-use patterns of blue sharks indicated they spend much of the time in areas where pelagic longlining activities are often highest, and in depth zones where these fisheries particularly target other species, which could account for the rapid declines recently reported for blue sharks in many parts of the world's oceans. Our results provide habitat targets for blue shark conservation that may also be relevant to other pelagic species.
由于过度捕捞，远洋鲨鱼物种的数量急剧减少，有些物种的数量现在只有历史生物量的一小部分。先进的遥测技术能够跟踪空间动态和行为，为受威胁物种的栖息地偏好提供基本信息，以帮助保护。我们使用弹出式卫星连接的档案标签跟踪东北大西洋最高的远洋渔业兼捕物种蓝鲨（Prionace glauca）的运动，以确定与栖息地相关的空间利用程度，并研究垂直生态位。总的来说，蓝鲨向标记地点（英吉利海峡；葡萄牙南部）的西南方向移动，表现出与局部生产力锋区相关的显著地点忠诚度，估计的空间利用模式与随机游动显著不同。跟踪的雌性鲨鱼在昼夜深度偏好方面表现出行为可变性，无论是个体内部还是个体之间。昼夜深度使用范围从正常昼夜垂直移动（nDVM；黎明下降，黄昏上升）到反向昼夜垂直移动（rDVM；黎明上升，黄昏下降），再到没有昼夜差异的行为模式。结果表明，蓝鲨在很长一段时间内占据了一些最具生产力的海洋区域，并在多个时空尺度上构建昼夜活动模式，以响应特定的栖息地类型。这样做，鲨鱼占据了与其大小相称的非常广泛的垂直深度范围（1.0-2.0 米叉长），从表面到深海区（最大潜水深度 1160 米）。蓝鲨的空间利用模式表明，它们大部分时间都在远洋延绳钓活动通常最高的区域，以及这些渔业特别针对其他物种的深度区域，这可能是最近在世界许多海洋地区报告的蓝鲨迅速减少的原因。我们的研究结果为蓝鲨保护提供了栖息地目标，这些目标可能也与其他远洋物种有关。
