Department of Natural Resource Sciences, McGill University, Sainte-Anne-de-Bellevue, QC, H9X 3V9, Canada.
Department of Ecoscience, Arctic Research Centre, Aarhus University, 4000, Roskilde, Denmark.
Sci Rep. 2022 May 13;12(1):7938. doi: 10.1038/s41598-022-11660-4.
Accurate diet estimates are necessary to assess trophic interactions and food web dynamics in ecosystems, particularly for apex predators like cetaceans, which can regulate entire food webs. Quantitative fatty acid analysis (QFASA) has been used to estimate the diets of marine predators in the last decade but has yet to be implemented on free-ranging cetaceans, from which typically only biopsy samples containing outer blubber are available, due to a lack of empirically determined calibration coefficients (CCs) that account for fatty acid (FA) metabolism. Here, we develop and validate QFASA for killer whales using full blubber from managed-care and free-ranging individuals. First, we compute full, inner, and outer blubber CCs from the FA signatures across the blubber layers of managed-care killer whales and their long-term diet items. We then run cross-validating simulations on the managed-care individuals to evaluate the accuracy of diet estimates by comparing full-depth and depth-specific estimates to true diets. Finally, we apply these approaches to subsistence-harvested killer whales from Greenland to test the utility of the method for free-ranging killer whales, particularly for the outer blubber. Accurate diet estimates for the managed-care killer whales were only achieved using killer whale-specific and blubber-layer-specific CCs. Modeled diets for the Greenlandic killer whales largely consisted of seals (75.9 ± 4.7%) and/or fish (20.4 ± 2.4%), mainly mackerel, which was consistent with stomach content data and limited literature on this population. Given the remote habitats and below surface feeding of most cetaceans, this newly developed cetacean-specific QFASA method, which can be applied to outer-layer biopsies, offers promise to provide a significant new understanding of diet dynamics of free-ranging odontocetes and perhaps other cetacean species throughout the world's oceans.
准确的饮食估计对于评估生态系统中的营养相互作用和食物网动态至关重要，特别是对于鲸鱼等顶级掠食者，它们可以调节整个食物网。在过去十年中，定量脂肪酸分析（QFASA）已被用于估计海洋捕食者的饮食，但由于缺乏经验确定的校准系数（CC）来解释脂肪酸（FA）代谢，因此尚未在自由游动的鲸目动物中实施。由于缺乏经验确定的校准系数（CC）来解释脂肪酸（FA）代谢，因此尚未在自由游动的鲸目动物中实施。在这里，我们使用来自受控护理和自由游动个体的完整鲸脂来开发和验证用于虎鲸的 QFASA。首先，我们通过对受控护理虎鲸及其长期饮食项目的鲸脂各层的 FA 特征来计算完整、内部和外部鲸脂 CC。然后，我们在受控护理个体上进行交叉验证模拟，通过将全深度和深度特定的估计值与真实饮食进行比较，来评估饮食估计的准确性。最后，我们将这些方法应用于格陵兰岛的狩猎鲸，以测试该方法对自由游动的虎鲸的实用性，特别是对外部鲸脂的实用性。只有使用虎鲸特异性和鲸脂层特异性 CC，才能对受控护理虎鲸进行准确的饮食估计。对格陵兰虎鲸的模拟饮食主要由海豹（75.9±4.7%）和/或鱼类（20.4±2.4%）组成，主要是鲭鱼，这与胃内容物数据和该种群的有限文献一致。鉴于大多数鲸目动物的偏远栖息地和表面下觅食，这种新开发的鲸类特异性 QFASA 方法，可应用于外部层活检，可以提供对自由游动的齿鲸和其他可能的鲸类物种饮食动态的重要新认识，遍布全球海洋。
