Fish fauna of the Pelotas River, Upper Uruguay River, southern Brazil

Abstract: The fish fauna of the Pelotas River, in the Upper Uruguay ecoregion of southern Brazil was inventoried. Samplings were performed quarterly between August 2013 and May 2014 at 14 sites in the Pelotas River and its tributaries, using gill nets of different mesh sizes, sein nets, cast nets and electrofishing. In total, 7,745 specimens were recorded, comprising 46 species, belonging to 13 families and five orders. Approximately 80% of the species belonged to the orders Characiformes and Siluriformes, as well as the families Characidae and Loricariidae, which included a greater number of species. Of the total species, 24% were endemic to the Upper Uruguay River, four were identified only at the genus level and none was considered non-native. Approximately, half of the 98 species previously recorded for the Upper Uruguay basin were also detected in this study. The tributaries of the Pelotas River exhibited different faunas with five exclusive species. Thirty species were present in both the tributaries and the main channel. In addition, higher species richness, as well as the presence of larger-sized species were observed in the main channel. Many of the species not restricted to the Upper Uruguay River have already been reported as part of the Taquari-Antas River fauna. However, the local biodiversity of this region is under several threats, such as land use and installation of small hydroelectric plants. These results highlight the importance of the conservation of plateau/upland rivers, especially in the Upper Uruguay ecoregion, which shows a peculiar fish fauna and endemism.

摘要：本研究对巴西南部乌拉圭河上游生态区内的佩洛塔斯河（Pelotas River）鱼类区系开展了系统性清查。研究于2013年8月至2014年5月期间按季度在佩洛塔斯河及其支流的14个采样点开展采样，采用不同网目尺寸的刺网、围网、撒网及电捕鱼法。本次调查共记录标本7745尾，隶属于5目13科46种。其中约80%的物种隶属于脂鲤目（Characiformes）与鲇形目（Siluriformes），物种丰富度最高的类群为脂鲤科（Characidae）与甲鲶科（Loricariidae）。在所记录的全部物种中，24%为乌拉圭河上游特有种，4个类群仅鉴定至属级水平，未发现外来物种。此前乌拉圭河上游流域曾记录98个物种，本次调查中约半数被再次检出。佩洛塔斯河支流的鱼类区系组成与干流存在显著差异，共包含5种仅分布于支流的特有物种；另有30种同时存在于支流与干流河道中。此外，干流的物种丰富度更高，且栖息有体型更大的鱼类类群。诸多分布范围不限于乌拉圭河上游的物种，此前已有记录见于塔夸里-安塔斯河（Taquari-Antas River）的鱼类区系中。但该区域的本地生物多样性正面临多重威胁，包括土地利用方式变更与小型水电站的建设。本研究结果凸显了高原/高地河流保护的重要性，尤其是乌拉圭河上游生态区——该区域拥有独特的鱼类区系与特有物种分布格局。