Abstract：
Accurate diet identification of top predators is crucial to fully understand their ecological roles. Compared to terrestrial animals, gathering dietary information from cetaceans is notoriously difficult. Here, we applied a multilocus metabarcoding approach to investigate the diet of vulnerable Indo-Pacific humpback dolphins and Indo-Pacific finless porpoises from the Pearl River Estuary (PRE), China. Our analyses identified 21 prey fish species from the 42 humpback dolphin stomachs, as well as 10 species of fish and 1 species of cephalopod from the 13 finless porpoise stomachs. All of the taxa were assigned to the species level, highlighting that the multimarker approach could facilitate species identification. Most of the prey species were small- and medium-sized fishes that primarily fed on zooplankton. The calculated similarity index revealed a moderated dietary overlap between the 2 cetaceans, presumably due to the feeding of the 2 predators in association with fishing vessels in the PRE. A more diverse diet was observed in humpback dolphins in the closed fishing season compared to the fishing season, implying the influence on the dolphin diet due to the availability of commercial fishery resources. However, according to the results of species rarefaction curves, our findings on the feeding habits of the 2 cetaceans are still limited by insufficient sample size and therefore should be interpreted with caution. This study represents a first attempt to apply the multilocus DNA metabarcoding technique in the diet analysis of small cetaceans, although more efforts are needed to improve this type of analysis.
摘要：
对顶级捕食者的准确饮食识别对于充分了解其生态作用至关重要。与陆生动物相比，收集鲸目动物的饮食信息是非常困难的。这里,我们应用了一种多基因座元编码方法来调查来自珠江口（PRE）的脆弱的印度太平洋座头海豚和印度太平洋江豚的饮食，中国。我们的分析从42个座头鲸海豚胃中确定了21种猎物，以及来自13只江豚胃的10种鱼和1种头足类。所有的分类单元都被分配到物种级别，强调多标记方法可以促进物种鉴定。大多数猎物是小型和中型鱼类，主要以浮游动物为食。计算的相似性指数显示2个鲸类之间的饮食重叠有所缓和，大概是由于PRE中与渔船有关的2个捕食者的摄食。与捕鱼季节相比，封闭捕鱼季节的座头海豚的饮食更加多样化，暗示由于商业渔业资源的可用性对海豚饮食的影响。然而,根据物种稀疏曲线的结果，我们对2种鲸目动物摄食习惯的研究结果仍然受到样本量不足的限制，因此应谨慎解释。这项研究代表了首次尝试将多位点DNA代谢编码技术应用于小型鲸目动物的饮食分析中，尽管需要更多的努力来改进这种类型的分析。
