ABSTRACT: Killer whales Orcinus orca have a cosmopolitan distribution with a broad diet ranging from fish to marine mammals. In Norway, killer whales are regularly observed feeding on overwintering Norwegian spring-spawning (NSS) herring Clupea harengus inside the fjords. However, their offshore foraging behavior and distribution are less well understood. In particular, it is not known to what degree they rely on the NSS herring stock when the herring move to deeper offshore waters. Satellite telemetry data from 29 male killer whales were analyzed to assess whether their offshore foraging behavior is linked to herring distribution. Unlike most marine predator-prey studies that use indirect proxies for prey abundance and distribution, our study utilized 2 herring density estimates based on (1) direct observations from acoustic trawl survey data and (2) simulations from a fully coupled ecosystem model. Mixed effects models were used to infer the effect of herring density and light intensity on whale movement patterns. Our results suggest that killer whales follow NSS herring over long distances along the coast from their inshore overwintering areas to offshore spawning grounds. All whales changed from fast, directed, to slow, non-directed movement when herring density increased, although individuals had different propensities towards movement. Our data indicated that whales continue to feed on herring along the Norwegian shelf. We conclude that NSS herring constitute an important prey resource for at least some killer whales in the northeastern Atlantic, not only during the herring overwintering period, but also subsequently throughout the herring spawning migration.

中文翻译：

---

挪威架子上的虎鲸运动与鲱鱼密度有关

摘要：虎鲸Orcinus orca具有世界性的分布，饮食范围广泛，从鱼类到海洋哺乳动物。在挪威，经常观察到虎鲸以越冬的挪威春季产卵鲱鱼Clupea harengus为食在峡湾里。然而，人们对它们的近海觅食行为和分布知之甚少。尤其是，当鲱鱼移至更深的近海水域时，他们在多大程度上依赖NSS鲱鱼种群尚不清楚。分析了来自29只雄性虎鲸的卫星遥测数据，以评估其近海觅食行为是否与鲱鱼分布有关。与大多数使用间接代理进行猎物丰富度和分布的海洋捕食者-猎物研究不同，我们的研究基于（1）声学拖网调查数据的直接观测值和（2）完全耦合的生态系统模型的模拟，使用了2种鲱鱼密度估计值。使用混合效应模型来推断鲱鱼密度和光照强度对鲸鱼运动模式的影响。我们的结果表明，虎鲸跟随NSS鲱鱼从沿海越冬地区到近海产卵场沿海岸长途航行。当鲱鱼密度增加时，所有鲸鱼都从快速，定向运动变为缓慢，非定向运动，尽管个体对运动的倾向不同。我们的数据表明，鲸鱼继续在挪威架子上以鲱鱼为食。我们得出的结论是，NSS鲱鱼不仅在鲱鱼越冬期间，而且在随后的整个鲱鱼产卵迁徙中，都是东北大西洋至少某些虎鲸的重要猎物资源。尽管个人对运动有不同的倾向。我们的数据表明，鲸鱼继续在挪威架子上以鲱鱼为食。我们得出的结论是，NSS鲱鱼不仅在鲱鱼越冬期间，而且在随后的整个鲱鱼产卵迁徙中，都是东北大西洋至少某些虎鲸的重要猎物资源。尽管个人对运动有不同的倾向。我们的数据表明，鲸鱼继续在挪威架子上以鲱鱼为食。我们得出的结论是，NSS鲱鱼不仅在鲱鱼越冬期间，而且在随后的整个鲱鱼产卵迁徙中，都是东北大西洋至少某些虎鲸的重要猎物资源。