The scalloped hammerhead shark Sphyrna lewini is a migratory species that exhibits complex patterns of spatial organization associated with the use of both coastal and oceanic habitats. Information about its movements and habitat use is fragmentary and recent study showed that elemental signatures deposited in its vertebrae served as reliable site-specific markers. Age-related movements of S. lewini in the Mexican Pacific were examined using vertebral microchemistry. Vertebrae were obtained from 48 sharks captured in 2016. Elemental signatures were quantified using laser ablation-inductively coupled plasma mass spectrometry. Spatial variability of the vertebral edge elemental signatures was first assessed to verify that microchemistry could distinguish among sharks based on recent habitat use before inferences on environmental histories could be made. Age-related movements were then assessed by quantifying changes in the Sr:Ca, Ba:Ca, Sr:Ba and Pb:Ca ratios along vertebral transects encompassing complete life histories. Analysis of elemental profiles suggested that S. lewini exhibits movements that are likely more plastic than previously assumed, with a stronger association to coastal habitats than expected. Females used highly variable habitats over their lifetime and males alternated between two migratory patterns, coastal or pelagic, as they either remained nearshore for their entire life or migrated offshore to later return to coastal habitats. Migratory contingents or partial migration might be a strategy of S. lewini to reduce vulnerability to stressors among regions. Scalloped hammerhead persistence in the Mexican Pacific, despite being heavily fished, may be linked to behavioral plasticity of movement rather than its life history characteristics.

中文翻译：

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基于脊椎微化学对扇形双髻鲨 Sphyrna lewini 迁移模式的新见解

扇形双髻鲨 Sphyrna lewini 是一种迁徙物种，表现出与利用沿海和海洋栖息地相关的复杂空间组织模式。关于其运动和栖息地使用的信息是零碎的，最近的研究表明，沉积在其椎骨中的元素特征是可靠的特定地点标记。使用脊椎微化学检查了墨西哥太平洋地区 S. lewini 与年龄相关的运动。从 2016 年捕获的 48 条鲨鱼中获得了椎骨。使用激光烧蚀电感耦合等离子体质谱法对元素特征进行了量化。首先评估脊椎边缘元素特征的空间变异性，以验证微化学可以根据最近的栖息地使用情况区分鲨鱼，然后才能对环境历史进行推断。然后通过量化 Sr:Ca、Ba:Ca、Sr:Ba 和 Pb:Ca 比率的变化来评估与年龄相关的运动，这些比率包括完整的生活史。元素剖面分析表明，S. lewini 表现出的运动可能比以前假设的更具可塑性，与沿海栖息地的关联比预期的要强。雌性在其一生中使用高度可变的栖息地，而雄性则在沿海或远洋两种迁徙模式之间交替，因为它们要么终生留在近岸，要么迁徙离岸，后来又返回沿海栖息地。迁徙队伍或部分迁徙可能是 S. lewini 减少区域间压力源脆弱性的一种策略。尽管被大量捕捞，墨西哥太平洋的扇形锤头鱼的持久性可能与运动的行为可塑性而不是其生活史特征有关。