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Abstract：
Masu salmon, Oncorhynchus masou (Brevoort 1856), a commercially important fish species endemic to the North Pacific Ocean, attained national second-level protected animal status in China in 2021. Despite this recognition, knowledge about the trophic ecology of this fish remains limited. This study investigated the diet diversity of fluviatile Masu salmon in the Mijiang River, China, utilizing the gastrointestinal tract environmental DNA (GITeDNA) metabarcoding and morphological identification. The results revealed a diverse prey composition, ranging from terrestrial and aquatic invertebrates to small fishes. The fluviatile Masu salmon in general consumed noteworthily more aquatic prey than terrestrial prey. There were much more prey taxa and a higher diet diversity detected by GITeDNA metabarcoding than by morphological identification. GITeDNA metabarcoding showed that larger and older Masu salmon consumed significantly more terrestrial insects than aquatic prey species did, with 7366 verses 5012 sequences in the group of ≥20 cm, 9098 verses 4743 sequences in the group of ≥100 g and 11,540 verses 729 sequences in the group of age 3+. GITeDNA metabarcoding also showed size- and age-related diet diversity, indicating that the dietary niche breadth and trophic diversity of larger and older Masu salmon increased with food resources expanding to more terrestrial prey. Terrestrial invertebrates of riparian habitats play a vital role in the diet of fluviatile Masu salmon, especially larger individuals, highlighting their importance in connecting aquatic and terrestrial food webs. Conservation plans should prioritize the protection and restoration of riparian habitats. This study advocates the combined use of GITeDNA metabarcoding and morphological observation for a comprehensive understanding of fish diet diversity.
摘要：
马苏鲑鱼,Oncorhynchusmasou（Brevoort1856），一种商业上重要的北太平洋特有的鱼类，2021年在中国获得国家二级保护动物地位。尽管有这样的认可,关于这种鱼的营养生态学的知识仍然有限。本研究调查了Mijiang河中轻浮的Masu鲑鱼的饮食多样性，中国,利用胃肠道环境DNA(GITeDNA)的元编码和形态学鉴定。结果显示了不同的猎物组成，从陆地和水生无脊椎动物到小鱼。一般来说，轻盈的Masu鲑鱼比陆地猎物消耗的水生猎物要多。与通过形态学鉴定相比，通过GITeDNAmetabarcoding检测到的猎物类群更多，饮食多样性更高。GITeDNA元编码表明，较大和较老的Masu鲑鱼比水生猎物物种消耗的陆生昆虫明显更多，在≥20厘米的组中有7366节和5012节序列，≥100g组中的9098对4743序列，3岁以上组中的11,540对729序列。GITeDNA代谢编码还显示了大小和年龄相关的饮食多样性，表明较大和较老的Masu鲑鱼的饮食生态位宽度和营养多样性随着食物资源的扩展而增加。河岸栖息地的陆地无脊椎动物在轻浮的Masu鲑鱼的饮食中起着至关重要的作用，尤其是较大的个体，强调它们在连接水生和陆地食物网中的重要性。保护计划应优先考虑保护和恢复河岸栖息地。本研究主张结合使用GITeDNA元转录编码和形态学观察，以全面了解鱼类饮食多样性。
