Dick Cory, Larson Wesley A, Karpan Kirby, Baetscher Diana S, Shi Yue, Sethi Suresh, Fangue Nann A, Henderson Mark J
California Cooperative Fish and Wildlife Research Unit, Department of Fisheries Biology, Humboldt State University, Arcata, California, USA.
Alaska Fisheries Science Center, Auke Bay Laboratories, National Oceanographic and Atmospheric Administration, National Marine Fisheries Service, Juneau, Alaska, USA.
Mol Ecol Resour. 2025 Jul;25(5):e13849. doi: 10.1111/1755-0998.13849. Epub 2023 Aug 9.
Diet analysis is a vital tool for understanding trophic interactions and is frequently used to inform conservation and management. Molecular approaches can identify diet items that are impossible to distinguish using more traditional visual-based methods. Yet, our understanding of how different variables, such as predator species or prey ration size, influence molecular diet analysis is still incomplete. Here, we conducted a large feeding trial to assess the impact that ration size, predator species, and temperature had on digestion rates estimated with visual identification, qPCR, and metabarcoding. Our trial was conducted by feeding two rations of Chinook salmon (Oncorhynchus tshawytscha) to two piscivorous fish species (largemouth bass [Micropterus salmoides] and channel catfish [Ictalurus punctatus]) held at two different temperatures (15.5 and 18.5°C) and sacrificed at regular intervals up to 120 h from the time of ingestion to quantify the prey contents remaining in the digestive tract. We found that ration size, temperature, and predator species all influenced digestion rate, with some indication that ration size had the largest influence. DNA-based analyses were able to identify salmon smolt prey in predator gut samples for much longer than visual analysis (~12 h for visual analysis vs. ~72 h for molecular analyses). Our study provides evidence that modelling the persistence of prey DNA in predator guts for molecular diet analyses may be feasible using a small set of controlling variables for many fish systems.
饮食分析是理解营养级相互作用的重要工具，并且经常被用于为保护和管理提供信息。分子方法能够识别出使用更传统的基于视觉的方法无法区分的饮食项目。然而，我们对于不同变量（如捕食者种类或猎物定量大小）如何影响分子饮食分析的理解仍不完整。在此，我们进行了一项大型摄食试验，以评估定量大小、捕食者种类和温度对通过视觉识别、定量聚合酶链反应（qPCR）和宏条形码分析估计的消化率的影响。我们的试验通过将两种定量的奇努克鲑鱼（Oncorhynchus tshawytscha）投喂给两种食鱼性鱼类（大口黑鲈[Micropterus salmoides]和斑点叉尾鮰[Ictalurus punctatus]）来进行，这两种食鱼性鱼类被饲养在两种不同温度（15.5和18.5°C）下，并在摄食后每隔一定时间处死，最长至120小时，以量化消化道中剩余的猎物含量。我们发现定量大小、温度和捕食者种类均影响消化率，有迹象表明定量大小的影响最大。基于DNA的分析能够在捕食者肠道样本中识别出鲑鱼幼鱼猎物的时间比视觉分析长得多（视觉分析约为12小时，而分子分析约为72小时）。我们的研究提供了证据，表明对于许多鱼类系统而言，使用一小部分控制变量来模拟分子饮食分析中猎物DNA在捕食者肠道中的持久性可能是可行的。
