Streams fish from Upper Araguaia and Middle Rio da Mortes basin, Brazil: generating subsidies for preservation and conservation of this critical natural resource

Abstract: The Araguaia River basin has the highest fish biodiversity within the Cerrado biome (Brazilian savannah), with many endemic and threatened species by human activities. Despite growing efforts to catalog Neotropical freshwater fish biodiversity, many regions are still undersampled. Our objective is to complement the information about stream fish in two hydrographic basins in the Cerrado. We sampled 72 streams with 50 m stretch in the Upper Araguaia (n = 32) and Middle Rio das Mortes (n = 40) basins. We collected 14,887 individuals distributed in 137 species, 81 genera, 30 families, and six orders. Characidae, Loricariidae, and Cichlidae were the families richer in species. We found a high diversity of rare fish species in the streams sampled, ca. 71.5% of the species had at least five individuals collected, and 18 species had only one collected specimen. The most frequent species were Astyanax cf. goyacensis, Knodus cf. breviceps, and Characidium cf. zebra. Both basins shared around 43% of the species. We caught 76 species in Upper Araguaia and 120 species in Middle Rio das Mortes. Seventeen exclusive fish species occurred in Upper Araguaia, whereas 61 were found in the Middle Rio das Mortes basin. Our analysis showed lower diversity of fish in Upper Araguaia than in the Middle Rio das Mortes basin. Considering the exclusive fish species of both basins, the human threats in those regions, and the few existent protected areas, we need a better look at the aquatic biodiversity conservation of this ecosystem.

摘要：阿拉瓜亚河流域是塞拉多生物群系（巴西稀树草原）内鱼类生物多样性最为丰富的区域，拥有大量受人类活动威胁的特有物种。尽管当前针对新热带区淡水鱼类生物多样性的编目工作不断推进，但诸多区域仍存在采样覆盖不足的问题。本研究旨在补充塞拉多地区两个水文流域的溪流鱼类基础数据。本次研究对阿拉瓜亚河上游（n=32）与莫尔特斯河中游（n=40）流域内的72条长度为50米的溪流开展采样，共采集到14887尾个体，隶属于6目30科81属137种。脂鲤科（Characidae）、甲鲶科（Loricariidae）与慈鲷科（Cichlidae）为物种丰富度最高的三个鱼类类群。本次采样的溪流中稀有鱼类物种多样性较高：约71.5%的物种采集到至少5尾个体，另有18个物种仅采集到1尾标本。优势物种为高氏丽脂鲤近似种（Astyanax cf. goyacensis）、短体克氏脂鲤近似种（Knodus cf. breviceps）以及条鳅鮊近似种（Characidium cf. zebra）。两个流域共享约43%的物种。阿拉瓜亚河上游共记录76种鱼类，莫尔特斯河中游则记录到120种鱼类。阿拉瓜亚河上游存在17种特有鱼类，而莫尔特斯河中游流域有61种特有鱼类。分析结果表明，阿拉瓜亚河上游的鱼类多样性低于莫尔特斯河中游流域。综合两个流域的特有鱼类物种、当地面临的人类活动威胁以及现存保护区数量稀少的现状，亟需加强该生态系统的水生生物多样性保护工作。