As apex predators, cetaceans play an essential ecological role in marine ecosystems. Fluctuations in the abundance of these top predators linked to human activities can have detrimental consequences for the entire ecosystem. Cetaceans face numerous anthropogenic threats that can have both short and long-term effects. To ensure their conservation, it is necessary to identify changes in seasonal distributions at small and large scales. We aimed to model the seasonal distribution of the most abundant cetacean species in the European Atlantic waters and the Mediterranean Sea by assembling datasets collected over 16 years of surveys using a standardised line-transect protocol. Data were homogenised, detection functions fitted and effective strip widths estimated. We extracted environmental variables integrated over the water column, which we transformed using a principal component analysis (PCA). The dimensions of the PCA were then integrated as explanatory variables in a generalised additive model, taking seasonal and spatial effects into account to predict the seasonal cetacean distribution. We were able to highlight changes in the spatial distribution and/or density of cetaceans throughout the year at a large scale, considering environmental extrapolation areas to predict where environmental variables were sampled during the surveys. For minke (Balaenoptera acutorostrata) and fin (B. physalus) whales, densities varied over the seasons but not the distribution, suggesting a seasonal migration outside the survey areas. For common dolphins (Delphinus delphis), bottlenose dolphins (Tursiops truncatus) and harbour porpoises (Phocoena phocoena), densities varied little but distributions did over the seasons. Finally, pilot whales (Globicephala spp), Risso’s (Grampus griseus) and striped (Stenella coeruleoalba) dolphins showed little seasonal variation in their distribution. Using monthly dynamic environmental variables at depth and PCA dimensions in habitat models, we produced maps of the seasonal distribution of cetaceans in the Mediterranean Sea and the European Atlantic waters to help fill gaps in our knowledge of cetacean distribution.

中文翻译：

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鲸类动物在欧洲大西洋和地中海水域的季节性分布


作为顶级捕食者，鲸类动物在海洋生态系统中发挥着重要的生态作用。这些与人类活动相关的顶级捕食者数量的波动可能会对整个生态系统产生不利影响。鲸类动物面临许多人为威胁，这些威胁可能产生短期和长期影响。为了确保它们的守恒性，有必要识别小尺度和大尺度的季节性分布变化。我们旨在通过使用标准化的线-样带协议收集 16 年调查中收集的数据集，对欧洲大西洋水域和地中海最丰富的鲸类物种的季节性分布进行建模。数据均质化，拟合检测函数并估计有效带材宽度。我们提取了在水柱上集成的环境变量，并使用主成分分析 （PCA） 对其进行转换。然后将 PCA 的维度作为解释变量整合到广义加法模型中，同时考虑季节性和空间效应以预测季节性鲸类分布。我们能够大尺度地突出鲸类动物全年空间分布和/或密度的变化，考虑环境外推区域以预测调查期间环境变量的采样位置。对于小须鲸 （Balaenoptera acutorostrata） 和长须鲸 （B. physalus） 来说，密度随季节变化，但分布不变化，这表明在调查区域之外进行了季节性迁移。对于普通海豚 （Delphinus delphis）、宽吻海豚 （Tursiops truncatus） 和港湾鼠海豚 （Phocoena phocoena），密度变化不大，但分布随季节变化。 最后，领航鲸 （Globicephala spp）、里索海豚 （Grampus griseus） 和条纹海豚 （Stenella coeruleoalba） 的分布几乎没有季节性变化。使用栖息地模型中的每月深度动态环境变量和 PCA 维度，我们制作了地中海和欧洲大西洋水域鲸类季节性分布图，以帮助填补我们对鲸类分布知识的空白。