Abstract With global increases in anthropogenic pressures on wildlife populations comes a responsibility to manage them effectively. The assessment of marine ecosystem health is challenging and often relies on monitoring indicator species, such as cetaceans. Most cetaceans are however highly mobile and spend the majority of their time hidden from direct view, resulting in uncertainty on even the most basic population metrics. Here, we discuss the value of long-term and internationally combined stranding records as a valuable source of information on the demographic and mortality trends of the harbour porpoise (Phocoena phocoena) in the North Sea. We analysed stranding records (n = 16,181) from 1990 to 2017 and demonstrate a strong heterogeneous seasonal pattern of strandings throughout the North Sea, indicative of season-specific distribution or habitat use, and season-specific mortality. The annual incidence of strandings has increased since 1990, with a notable steeper rise particularly in the southern North Sea since 2005. A high density of neonatal strandings occurred specifically in the eastern North Sea, indicative of areas important for calving, and large numbers of juvenile males stranded in the southern parts, indicative of a population sink or reflecting higher male dispersion. These findings highlight the power of stranding records to detect potentially vulnerable population groups in time and space. This knowledge is vital for managers and can guide, for example, conservation measures such as the establishment of time-area-specific limits to potentially harmful human activities, aiming to reduce the number and intensity of human-wildlife conflicts.

中文翻译：

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小型鲸类的时空死亡率和人口趋势：搁浅以告知保护管理

摘要 随着全球人为压力对野生动物种群的增加，有效管理它们的责任随之而来。海洋生态系统健康的评估具有挑战性，通常依赖于监测指标物种，例如鲸类。然而，大多数鲸类动物的移动性很强，大部分时间都隐藏在视线之外，导致即使是最基本的种群指标也存在不确定性。在这里，我们讨论了长期和国际合并搁浅记录作为有关北海港湾鼠海豚 (Phocoena phocoena) 人口统计和死亡率趋势的宝贵信息来源的价值。我们分析了 1990 年至 2017 年的搁浅记录（n = 16,181），并展示了整个北海搁浅的强烈异质季节性模式，指示特定季节的分布或栖息地使用，以及特定季节的死亡率。自 1990 年以来，搁浅的年发生率一直在增加，自 2005 年以来，尤其是在北海南部出现了显着的急剧上升。尤其是在北海东部，新生儿搁浅的发生率很高，这表明该地区对产犊很重要，而且大量的幼仔男性滞留在南部，表明人口下降或反映男性分散程度更高。这些发现突出了搁浅记录在时间和空间上检测潜在脆弱人群的能力。这些知识对管理人员至关重要，例如可以指导保护措施，例如为可能有害的人类活动建立特定时间区域的限制，