The Yarlung Zangbo River is the largest river on the Tibetan Plateau, which is considered a hotspot of biodiversity conservation efforts. In this study, the fish fauna of the middle and lower Yarlung Zangbo River was investigated, to explore the species composition and spatial patterns of fish assemblages as well as the associated environmental factors. Thirty-four sites across an elevation of 589 to 3410 m were sampled in 2015 and 2016. A total of 35 species—28 native and seven exotic—was collected. Of these species, four were described for the first time, 14 were endemic to the Yarlung Zangbo-Brahmaputra River drainage and five are considered endangered. Cluster analysis revealed significant spatial changes in fish assemblages along the longitudinal gradient. Two site-groups separated by the Yarlung Zangbo Grand Canyon were identified, corresponding to midstream and downstream. In the midstream, fish assemblages were characterized by typical plateau fish species (e.g., Schizopygopsis younghusbandi, Schizothorax oconnori, Triplophysa stenura, Triplophysa brevicauda, Schizothorax macropogon, Triplophysa tibetana and Ptychobarbus dipogon), while in the downstream fish assemblages were characterized jointly by plateau species (e.g., Schizothorax curilabiatus and Schizothorax molesworthi) and oriental species (e.g., Garra tibetana, Psilorhynchus homaloptera, Pseudecheneis sulcata, Exostoma tenuicaudata, Parachiloglanis hodgarti, Neolissochilus hexagonolepis and Garra yajiangensis). Canonical correspondence analysis (CCA) showed that altitude, channel width and the density of macroinvertebrates were the main environmental factors determining the spatial distribution of fish assemblages. This study is an important step towards understanding fish assemblages in the middle and lower Yarlung Zangbo River and will help with future efforts to protect aquatic communities and their habitats.

雅鲁藏布江是青藏高原最大的河流，被认为是生物多样性保护工作的热点。本研究对雅鲁藏布江中下游鱼类区系进行了调查，以探讨鱼类种群的种类组成和空间格局以及相关的环境因素。在2015年和2016年，对海拔589至3410 m的34个地点进行了采样。总共采集了35种，其中28种为本地物种，而7种为外来物种。在这些物种中，首次描述了四种，雅鲁藏布江-布拉马普特拉河流域特有的14种，其中五种被认为是濒临灭绝的。聚类分析揭示了沿纵向梯度的鱼类组合的显着空间变化。确定了由雅鲁藏布江大峡谷隔开的两个遗址群，对应于中游和下游。在中游，鱼类种群的特征是典型的高原鱼类（例如，拉萨裸裂尻鱼，裂oconnori，鳅stenura，鳅brevicauda，裂macropogon，鳅tibetana和Ptychobarbus dipogon），而在下游鱼组合物共同通过高原物种（例如，其特征在于裂curilabiatus和裂molesworthi）和东方物种（例如，墨头tibetana，Psilorhynchus homaloptera，Pseudecheneis苏卡达，Exostoma tenuicaudata，平唇鮡，Neolissochilus hexagonolepis和Garra yajiangensis（）。典型对应分析（CCA）表明，高度，河道宽度和大型无脊椎动物的密度是决定鱼群空间分布的主要环境因素。这项研究是了解雅鲁藏布江中下游鱼群的重要一步，并将有助于未来保护水生生物及其栖息地的努力。