1. Providing taxonomically precise dietary characterisations for freshwater fish species is critical for gaining a deeper understanding of the trophic dynamics present in freshwater ecosystems. However, our current understanding of freshwater trophic ecology has relied almost entirely upon direct observation of foraging attempts or morphological identification of partially digested prey. Due to the limitations of morphological dietary characterisations of soft‐bodied arthropod prey, these techniques offer dietary descriptions that can lack satisfactory taxonomic resolution and may bias our interpretations of freshwater food webs.
2. Recent advancements in DNA‐based prey identification have allowed for species‐level prey characterisations for many terrestrial insectivores, although these techniques have seldom been applied to understand the diets of freshwater fish. This study used DNA metabarcoding with high‐throughput, next‐generation sequencing to provide species‐level descriptions of prey composition for three naturally reproducing, syntopic freshwater trout species.
3. Our study supports previous findings that suggested that brook trout (Salvelinus fontinalis), brown trout (Salmo trutta), and rainbow trout (Oncorhynchus mykiss) are generalist predators that display a high degree of seasonal dietary flexibility. Prey composition varied significantly across sampling periods, with detection frequency of terrestrial prey greater in the spring/summer period compared to the autumn period.
4. Pollution‐sensitive aquatic macroinvertebrates were detected frequently across both sampling periods, highlighting the importance of high‐quality streams that support such arthropod prey. DNA metabarcoding also detected a high richness of soft‐bodied, Lepidoptera prey species, a taxonomic group that has been largely underrepresented in previous trout dietary studies that used traditional morphological techniques.
5. This study demonstrates the applicability of dietary DNA metabarcoding for the detection and species‐level identification of arthropods found in freshwater fish lavage samples and highlights the importance of taxonomically precise techniques when attempting to better understand trophic interactions within freshwater communities.

中文翻译：

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饮食DNA元条形码揭示了三种同位淡水鳟鱼物种的季节性营养变化

1. 为淡水鱼类提供分类学上精确的饮食特征对于深入了解淡水生态系统中的营养动态至关重要。但是，我们目前对淡水营养生态学的理解几乎完全依赖于对觅食尝试的直接观察或对部分消化的猎物的形态学鉴定。由于软体动物节肢动物猎物的形态学饮食特征存在局限性，因此这些技术提供的饮食描述可能缺乏令人满意的分类学分辨率，并可能使我们对淡水食物网的解释产生偏差。
2. 尽管很少使用这些技术来了解淡水鱼的饮食，但基于DNA的猎物识别技术的最新进展已使许多陆生食虫动物的物种级猎物得以表征。这项研究使用了具有高通量下一代测序的DNA元条形码技术，为三种天然繁殖的同位淡水鳟鱼物种提供了猎物组成的物种级描述。
3. 我们的研究支持以前的发现，表明溪鳟（Salvelinus fontinalis），褐鳟（Salmo trutta）和虹鳟（Oncorhynchus mykiss）是通才动物，它们显示出高度的季节性饮食灵活性。在整个采样周期内，猎物的组成变化很大，与秋季相比，春季/夏季的陆地猎物检测频率更高。
4. 在两个采样期间内，经常检测到对污染敏感的水生无脊椎动物，这突出了支持这种节肢动物猎物的高质量水流的重要性。DNA元条形码技术还检测到了丰富的鳞翅目捕食者，这是一个分类组，在以前使用传统形态学技术进行的鳟鱼饮食研究中，该分类组的代表性不足。
5. 这项研究证明了饮食DNA元条形码技术在淡水鱼灌洗样品中发现和检测节肢动物的适用性，并强调了试图更好地了解淡水群落中营养相互作用的分类学精确技术的重要性。