Scripps Institution of Oceanography, La Jolla, CA, USA; North Coast Cetacean Society, Hartley Bay, British Columbia, Canada.
North Coast Cetacean Society, Hartley Bay, British Columbia, Canada.
Mar Environ Res. 2018 Sep;140:180-189. doi: 10.1016/j.marenvres.2018.06.014. Epub 2018 Jun 18.
We used ecosystem sampling during systematic surveys and opportunistic focal follows, comparison tests, and random forest models to evaluate fin whale (Balaenoptera physalus) and humpback whale (Megaptera novaeangliae) habitat associations within an inland feeding ground (Kitimat Fjord System, British Columbia, Canada). Though these species are sympatric and share a common prey source, they were attuned to different aspects of the local habitat. The fin whales were associated with habitat properties reminiscent of the open ocean. Humpback whales, in contrast, were associated with features more commonly associated with the inland waters of fjords. Fixed habitat features, such as seafloor depth and distance from the fjord mouth, were the most important predictors of fin whale presence, but fixed and dynamic variables, such as surface properties, predicted humpback whale presence with equal (moderate) success. With the exception of strong salinity gradients for humpback whales, habitat conditions were poor predictors of feeding state. Fin whales practiced a spatially confined, seasonally stable, and thus more predictable use of certain channels within the fjord system. These findings are compatible with site loyal behavior, which is interesting in light of the species' historical, unique use of this fjord system. The relatively lackluster performance of humpback-habitat models, coupled with the importance of oceanographic properties, makes the humpback's habitat use strategy more uncertain. The fact that two sympatric species sharing a common prey source exhibited different habitat use strategies suggests that at least one species was informed by something in addition to prey. Given that the two species are attuned to different aspects of the fjord habitat, their responses to habitat changes, including anthropogenic impacts, would likely be different in both nature and degree. Our findings highlight the value of comparative studies and the complexity of rorqual habitat use, which must be understood in order for critical habitat to be identified and protected.
我们在系统调查中使用了生态系统采样以及机会性焦点跟踪、对比测试和随机森林模型，以评估在一个内陆觅食场（不列颠哥伦比亚省基蒂马特峡湾系统，加拿大）内长须鲸（Balaenoptera physalus）和座头鲸（Megaptera novaeangliae）的栖息地关联。尽管这两个物种是同域的，并且共享共同的猎物来源，但它们对当地栖息地的不同方面有所适应。长须鲸与具有开阔海洋特征的栖息地特征相关，而座头鲸则与峡湾内陆水域相关的特征相关。固定的栖息地特征，如海底深度和与峡湾口的距离，是长须鲸存在的最重要预测因子，但固定和动态变量，如地表特征，也以同样（中等）的成功率预测了座头鲸的存在。除了座头鲸的强盐度梯度外，栖息地条件对觅食状态的预测能力较差。长须鲸在峡湾系统内的某些通道中表现出空间受限、季节性稳定的、因此更可预测的使用模式。这些发现与该物种对该峡湾系统的历史上独特的使用有关，与基于地点的行为一致。座头鲸栖息地模型相对较差的性能，再加上海洋学特性的重要性，使得座头鲸的栖息地使用策略更加不确定。两个同域的物种共享共同的猎物来源，但表现出不同的栖息地使用策略，这表明至少有一种物种的行为不仅受到猎物的影响。鉴于这两个物种对峡湾栖息地的不同方面有所适应，它们对栖息地变化的反应（包括人为影响）在性质和程度上可能会有所不同。我们的研究结果突出了比较研究的价值和须鲸栖息地使用的复杂性，为了确定和保护关键栖息地，必须了解这些内容。
