Data from: Humpback whales feed on hatchery-released juvenile salmon

Humpback whales are remarkable for the behavioural plasticity of their feeding tactics and the diversity of their diets. Within the last decade at hatchery release sites in Southeast Alaska, humpback whales have begun exploiting juvenile salmon, a previously undocumented prey. The anthropogenic source of these salmon and their important contribution to local fisheries makes the emergence of humpback whale predation a concern for the Southeast Alaska economy. Here, we describe the frequency of observing humpback whales, examine the role of temporal and spatial variables affecting the probability of sighting humpback whales and describe prey capture behaviours at five hatchery release sites. We coordinated twice-daily 15 min observations during the spring release seasons 2010–2015. Using logistic regression, we determined that the probability of occurrence of humpback whales increased after releases began and decreased after releases concluded. The probability of whale occurrence varied among release sites but did not increase significantly over the 6 year study period. Whales were reported to be feeding on juvenile chum, Chinook and coho salmon, with photographic and video records of whales feeding on coho salmon. The ability to adapt to new prey sources may be key to sustaining their population in a changing ocean.

座头鲸（Humpback whales）以其觅食策略的行为可塑性与食谱多样性而著称。在过去十年间，阿拉斯加东南部的孵化场放流点周边，座头鲸开始捕食幼年鲑鱼——这是此前未被记录的猎物类型。由于这些鲑鱼属于人为放养种群，且对当地渔业贡献重大，座头鲸捕食行为的出现引发了阿拉斯加东南部地区的经济担忧。本研究针对5处孵化场放流点，描述了座头鲸的观测频次，分析了影响座头鲸目击概率的时空变量作用，并记录了其捕食行为。研究团队在2010至2015年的春季放流季期间，每日开展两次、每次15分钟的观测工作。通过逻辑回归分析，我们发现座头鲸的出现概率在放流启动后上升，放流结束后下降。不同放流点的座头鲸出现概率存在差异，但在整个6年的研究周期内并未出现显著上升。据观测，座头鲸的捕食对象为幼年马苏大麻哈鱼（chum salmon）、大鳞大麻哈鱼（Chinook salmon）与银大麻哈鱼（coho salmon），且有照片与视频记录证实座头鲸捕食银大麻哈鱼的行为。在不断变化的海洋环境中，适应新猎物来源的能力或许是维持座头鲸种群存续的关键。