Wang Sai, Wang Tuan-Tuan, Tang Jin-Peng, Wang Lin, Yang Yang, Lin Hsing-Juh, Chang Hao-Yen, Zhou Xing-An, Li Xing, Wang Ming
Research Center of Hydrobiology Department of Ecology Jinan University Guangzhou China.
Research Center of Tropical and Subtropical Aquatic Ecological Engineering Ministry of Education Engineering Jinan University Guangzhou China.
Ecol Evol. 2018 Nov 26;8(23):11467-11483. doi: 10.1002/ece3.4577. eCollection 2018 Dec.
Due to the heterogeneous distribution of resources along large rivers, understanding prey utilization by basin-scale fish assemblages remains a challenge, and thus, recognizing regional fish trophic guilds and indicator species is important. We analyzed the stomach contents of 96 fish species along the subtropical East River in China and identified 8 prey items (29 subcategories). Site-specific differences in fish diet composition (DC) revealed longitudinal shifts in utilized prey taxa, from upstream lotic to downstream semi-lentic items, and these were characterized by a decrease in the proportions of epilithic diatoms and aquatic insect larvae (Ephemeroptera and Chironomidae) accompanied by an increase in bivalves ( and ), shrimps and fishes, and organic sediments. The relative prey consumption weighted by fish abundance and biomass indicated that decreasing insect consumption and increasing detritus consumption were two fundamental vectors governing fish-centered feeding pathways. Seventeen prey-oriented fish guilds that were clustered based on DC matrix determined the spatial variation in the fish trophic structure. The cumulative presence of (a) upstream guilds reliant on insects and epiphytes, (b) midstream guilds reliant on hydrophytes, molluscs, and nekton, and (c) downstream guilds reliant on detritus, annelids, and plankton resulted in a longitudinal increase in guild richness, but this continuity was interrupted near the industrialized estuary. The most abundant 28 fish species across the guilds were selected as trophic indicator species; their spatial distribution significantly (0.05) explained >80% of the environmental and prey variables identified. These species signified the availability of predator-prey links in distinct habitats and the key environmental factors supporting these links. With a high contribution (>51%) of exotic species, an increase in detritivores downstream distinguishes the subtropical East River from temperate rivers. Particularly, in the disturbed lower reaches, the dominance of detritivores prevailed over the predicted increase in other feeding groups (e.g., omnivores and carnivores).
由于大型河流沿线资源分布不均，了解流域尺度鱼类群落对猎物的利用情况仍然是一项挑战，因此，识别区域鱼类营养类群和指示物种很重要。我们分析了中国亚热带东江沿线96种鱼类的胃内容物，识别出8种猎物类型（29个亚类）。鱼类饮食组成（DC）的特定地点差异揭示了所利用猎物类群的纵向变化，从上游流水型猎物到下游半静水型猎物，其特征是附生硅藻和水生昆虫幼虫（蜉蝣目和摇蚊科）的比例下降，同时双壳类（和）、虾类、鱼类以及有机沉积物的比例增加。以鱼类丰度和生物量加权的相对猎物消费量表明，昆虫消费量的减少和碎屑消费量的增加是主导以鱼类为中心的摄食路径的两个基本向量。基于DC矩阵聚类的17个以猎物为导向的鱼类类群决定了鱼类营养结构的空间变化。（a）依赖昆虫和附生植物的上游类群、（b）依赖水生植物、软体动物和自游生物的中游类群以及（c）依赖碎屑、环节动物和浮游生物的下游类群的累积出现导致类群丰富度沿纵向增加，但这种连续性在工业化河口附近被打断。在这些类群中最丰富的28种鱼类被选为营养指示物种；它们的空间分布显著（0.05）解释了所识别的>80%的环境和猎物变量。这些物种表明了不同栖息地中捕食者 - 猎物联系的可用性以及支持这些联系的关键环境因素。外来物种的贡献率很高（>51%），下游碎屑食性动物的增加使亚热带东江有别于温带河流。特别是在受到干扰的下游，碎屑食性动物的优势超过了其他摄食群体（如杂食动物和肉食动物）预计的增加。
