Klöcker C Antonia, Albert Ole Thomas, Ferter Keno, Bjelland Otte, Lennox Robert J, Albretsen Jon, Pohl Lotte, Dahlmo Lotte Svengård, Queiroz Nuno, Junge Claudia
Havforskningsinstituttet (Institute of Marine Research, IMR), P.O. Box 1870, 5817, Nordnes, Bergen, Norway.
Ocean Tracking Network, Dalhousie University, 1355 Oxford St, Halifax, NS, Canada.
Mov Ecol. 2024 Sep 6;12(1):62. doi: 10.1186/s40462-024-00498-2.
Studying habitat use and vertical movement patterns of individual fish over continuous time and space is innately challenging and has therefore largely remained elusive for a wide range of species. Amongst sharks, this applies particularly to smaller-bodied and less wide-ranging species such as the spurdog (Squalus acanthias Linnaeus, 1758), which, despite its importance for fisheries, has received limited attention in biologging and biotelemetry studies, particularly in the North-East Atlantic.
To investigate seasonal variations in fine-scale niche use and vertical movement patterns in female spurdog, we used archival data from 19 pregnant individuals that were satellite-tagged for up to 365 days in Norwegian fjords. We estimated the realised niche space with kernel densities and performed continuous wavelet analyses to identify dominant periods in vertical movement. Triaxial acceleration data were used to identify burst events and infer activity patterns.
Pregnant females frequently utilised shallow depths down to 300 m at temperatures between 8 and 14 °C. Oscillatory vertical moments revealed persistent diel vertical migration (DVM) patterns, with descents at dawn and ascents at dusk. This strict normal DVM behaviour dominated in winter and spring and was associated with higher levels of activity bursts, while in summer and autumn sharks predominantly selected warm waters above the thermocline with only sporadic dive and bursts events.
The prevalence of normal DVM behaviour in winter months linked with elevated likely foraging-related activity bursts suggests this movement behaviour to be foraging-driven. With lower number of fast starts exhibited in warm waters during the summer and autumn months, habitat use in this season might be rather driven by behavioural thermoregulation, yet other factors may also play a role. Individual and cohort-related variations indicate a complex interplay of movement behaviour and habitat use with the abiotic and biotic environment. Together with ongoing work investigating fine-scale horizontal movement as well as sex- and age-specific differences, this study provides vital information to direct the spatio-temporal distribution of a newly reopened fishery and contributes to an elevated understanding of the movement ecology of spurdog in the North-East Atlantic and beyond.
研究个体鱼类在连续的时间和空间中的栖息地利用和垂直运动模式具有内在的挑战性，因此，对于许多物种来说，这在很大程度上仍然难以捉摸。在鲨鱼中，这尤其适用于体型较小、活动范围较窄的物种，如角鲨（Squalus acanthias Linnaeus，1758），尽管它对渔业很重要，但在生物记录和生物遥测研究中受到的关注有限，特别是在东北大西洋。
为了研究雌性角鲨在精细尺度生态位利用和垂直运动模式的季节性变化，我们使用了19只怀孕个体的存档数据，这些个体在挪威峡湾被卫星标记长达365天。我们用核密度估计实际生态位空间，并进行连续小波分析以确定垂直运动的主导周期。利用三轴加速度数据识别爆发事件并推断活动模式。
怀孕的雌性角鲨经常在温度为8至14摄氏度的浅水区活动，深度可达300米。振荡垂直运动显示出持续的昼夜垂直迁移（DVM）模式，黎明时下降，黄昏时上升。这种严格的正常DVM行为在冬季和春季占主导地位，并且与较高水平的活动爆发相关，而在夏季和秋季，鲨鱼主要选择温跃层以上的温暖水域，只有零星的潜水和爆发事件。
冬季正常DVM行为的普遍存在以及与觅食相关的活动爆发增加表明这种运动行为是由觅食驱动的。在夏季和秋季的温暖水域中快速启动的次数较少，这个季节的栖息地利用可能更多地是由行为体温调节驱动的，但其他因素也可能起作用。个体和群体相关的差异表明运动行为和栖息地利用与非生物和生物环境之间存在复杂的相互作用。连同正在进行的调查精细尺度水平运动以及性别和年龄特异性差异的工作，本研究提供了重要信息，以指导新重新开放渔业的时空分布，并有助于提高对东北大西洋及其他地区角鲨运动生态学的理解。
