Animal dietary information provides the foundation for understanding trophic relationships, which is essential for ecosystem management. Yet, in marine systems, high‐resolution diet reconstruction tools are currently under‐developed. This is particularly pertinent for large marine vertebrates, for which direct foraging behaviour is difficult or impossible to observe and, due to their conservation status, the collection of stomach contents at adequate sample sizes is frequently impossible. Consequently, the diets of many groups, such as sharks, have largely remained unresolved. To address this knowledge gap, we applied metabarcoding to prey DNA in faecal residues (fDNA) collected on cotton swabs from the inside of a shark's cloaca. We used a previously published primer set targeting a small section of the 12S rRNA mitochondrial gene to amplify teleost prey species DNA. We tested the utility of this method in a controlled feeding experiment with captive juvenile lemon sharks (Negaprion brevirostris) and on free‐ranging juvenile bull sharks (Carcharhinus leucas). In the captive trial, we successfully isolated and correctly identified teleost prey DNA without incurring environmental DNA contamination from the surrounding seawater. In the field, we were able to reconstruct high‐resolution teleost dietary information from juvenile C. leucas fDNA that was generally consistent with expectations based on published diet studies of this species. While further investigation is needed to validate the method for larger sharks and other species, it is expected to be broadly applicable to aquatic vertebrates and provides an opportunity to advance our understanding of trophic interactions in marine and freshwater systems.

中文翻译：

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用泄殖腔拭子的 DNA 元条形码阐明鲨鱼的饮食

动物饮食信息为理解营养关系提供了基础，这对生态系统管理至关重要。然而，在海洋系统中，高分辨率饮食重建工具目前尚未开发。这对于大型海洋脊椎动物尤其重要，因为它们很难或不可能观察到直接觅食行为，而且由于它们的保护状态，通常不可能以足够的样本量收集胃内容物。因此，鲨鱼等许多群体的饮食在很大程度上仍未得到解决。为了解决这一知识差距，我们将元条形码应用于从鲨鱼泄殖腔内部的棉签上收集的粪便残留物 (fDNA) 中的猎物 DNA。我们使用以前发表的引物组靶向 12S rRNA 线粒体基因的一小部分来扩增硬骨鱼猎物物种 DNA。我们在圈养幼年柠檬鲨的控制喂养实验中测试了这种方法的实用性。Negaprion brevirostris）和自由放养的幼年牛鲨（Carcharhinus leucas）。在圈养试验中，我们成功地分离并正确识别了硬骨鱼猎物 DNA，而没有受到周围海水的环境 DNA 污染。在现场，我们能够从幼鱼C重建高分辨率硬骨鱼饮食信息。 leucas fDNA 与基于已发表的该物种饮食研究的预期基本一致。虽然需要进一步调查来验证大型鲨鱼和其他物种的方法，但预计该方法将广泛适用于水生脊椎动物，并提供机会促进我们对海洋和淡水系统中营养相互作用的理解。