Global warming is causing rapid change in marine food webs, particularly at northern latitudes where temperatures are increasing most rapidly. In this study, the diet of common minke whales was assessed both in terms of short-term (morphological analyses of digestive tract contents) and longer-term (tissue chemical markers: fatty acids and stable isotopes) prey use in the northern Barents Sea to see if they are prey shifting. Samples (blubber cores, muscle, and stomach contents) were obtained from 158 common minke whales taken during Norwegian commercial whaling operations during summer over the period 2016–2020. Two prey items, capelin and krill (primarily sp.), dominated the stomach contents in the entire period of investigation, which included sampling both in June and in August, similar to findings from earlier studies. A few gadoids were also observed in the whale stomachs. Lower blubber fatty acid (FA) contents in 2016/2017 as compared with 2018/2019 were observed. This is most likely explained by differences in sampling time (June in 2016/2017 vs August in 2018/2019, i.e., after a longer feeding period during the summer in the latter case). This explanation also fits with the fact that FA profiles of the 2018/2019 whales were more similar to the FA profiles of the potential prey, presumably reflecting the two months longer assimilation time for these whales. Multidimensional mixing models based on carbon and nitrogen isotope composition of the most likely prey groups suggested that the whales ate mostly krill in four of the five sampling years. In 2018 there were indications of a higher proportion of gadoid fish, showing some dietary flexibility. The trophic level of the whales’ feeding, as interpreted from the nitrogen isotope values, was positively correlated with blubber thickness suggesting that fish-eaters tended to assimilate more energy than whales that focused more exclusively on lower trophic prey. The variation suggested by different dietary analyses methods − stomach contents, fatty acids, and stable isotopes – most likely reflects different turnover times, with muscle stable isotopes likely representing several months of dietary integration, while lipid stores are more dynamic and may represent weeks, and stomach contents represent feeding events during the last few hours. The change in diet of minke whales from small pelagic fishes (in the past) to a greater quantity of krill and demersal fish (seen in this study) suggests that the whales are responding to the ongoing borealization of the Barents Sea ecosystem.

中文翻译：

---

夏季巴伦支海北部常见小须鲸（Balaenoptera acutorostrata）与其猎物之间的营养相互作用


全球变暖正在导致海洋食物网迅速变化，特别是在气温上升最快的北纬地区。在这项研究中，从巴伦支海北部的短期（消化道内容物的形态分析）和长期（组织化学标记：脂肪酸和稳定同位素）猎物使用方面评估了普通小须鲸的饮食，以看看它们是否正在转移猎物。样本（鲸脂核、肌肉和胃内容物）取自 2016 年至 2020 年夏季挪威商业捕鲸作业期间采集的 158 头普通小须鲸。在整个调查期间（包括六月和八月的采样），两种猎物，毛鳞鱼和磷虾（主要是磷虾）在胃内容物中占主导地位，这与早期研究的结果相似。在鲸鱼的胃中也观察到了一些鲹鱼。与 2018/2019 年相比，2016/2017 年的鲸脂脂肪酸 (FA) 含量较低。这很可能是由于采样时间的差异所致（2016/2017 年 6 月与 2018/2019 年 8 月，即后一种情况是在夏季较长的喂养期之后）。这一解释也符合这样一个事实，即 2018/2019 年鲸鱼的 FA 特征与潜在猎物的 FA 特征更相似，大概反映了这些鲸鱼的同化时间延长了两个月。基于最有可能的猎物群体的碳和氮同位素组成的多维混合模型表明，鲸鱼在五个采样年中有四年主要吃磷虾。 2018 年，有迹象表明鲹科鱼的比例较高，显示出一定的饮食灵活性。 根据氮同位素值的解释，鲸鱼摄食的营养级与鲸脂厚度呈正相关，这表明食鱼者往往比更专注于低营养级猎物的鲸鱼吸收更多的能量。不同饮食分析方法（胃内容物、脂肪酸和稳定同位素）所显示的变化很可能反映了不同的周转时间，肌肉稳定同位素可能代表几个月的饮食整合，而脂质储存则更具动态性，可能代表几周，并且胃内容物代表过去几个小时内的进食事件。小须鲸的饮食变化从小型中上层鱼类（过去）到更多的磷虾和底层鱼类（在本研究中看到）表明鲸鱼正在对巴伦支海生态系统持续的北方化做出反应。