Fish fauna in forested and rural streams from an ecoregion of high endemism, lower Iguaçu River basin, Brazil

Abstract The fish fauna of eight streams with different land uses of their watersheds (forested and rural areas) in the lower Iguaçu River basin was inventoried, in order to evaluate the composition and species richness. The fishes were sampled quarterly from May 2015 to February 2016, using the electrofishing technique. In total, 4,239 individuals were captured, belonging to six orders, 11 families and 26 species. The orders Siluriformes and Characiformes, and the families Characidae and Trichomycteridae were the most specious. Of the total species sampled, 65% were endemic to the Iguaçu River basin, four are not described and four are non-native. As expected to the Iguaçu River basin, the inventoried fauna revealed low richness and high endemism, however was highly nested within the species composition reported for main channel of Iguaçu River and their larger tributaries. The species recorded here corresponded to a subset of 24.5% of the 106 species documented for the basin. The streams presented different faunas, with only two species (Astyanax bifasciatus and Trichomycterus stawiarski) common to both forested and rural streams. In addition, higher species richness was recorded in streams inserted in conservation units. The presence of non-native species was more frequent in rural streams. These results highlight the importance of the preservation of forested areas in the watersheds of lower Iguaçu, which presents a peculiar fish fauna, along with several threats to biodiversity such as habitat loss by intensive agriculture use.

摘要：对伊瓜苏河下游流域内8条流域土地利用类型分别为森林区与乡村区的溪流开展鱼类区系普查，旨在评估其鱼类组成与物种丰富度。研究于2015年5月至2016年2月间每季度采用电渔法（electrofishing）进行鱼类采样，共计捕获4239尾个体，隶属于6目、11科共26种。其中鲇形目（Siluriformes）与脂鲤目（Characiformes），以及脂鲤科（Characidae）、毛鼻鲇科（Trichomycteridae）为物种丰富度最高的类群。在所采集的全部物种中，65%为伊瓜苏河下游流域特有种，4种尚未被正式描述，另有4种为外来物种。正如伊瓜苏河下游流域的典型特征，本次调查的鱼类区系呈现较低的物种丰富度与极高的特有性，但其物种组成高度嵌套于伊瓜苏河干流及其较大支流已报道的物种组成框架内。本次记录的物种仅占该流域已记载的106种鱼类的24.5%。两类溪流的鱼类区系存在显著分化，仅双线丽脂鲤（Astyanax bifasciatus）和斯陶尔毛鼻鲇（Trichomycterus stawiarski）这2个物种同时分布于森林区与乡村区溪流中。此外，位于保护地内的溪流物种丰富度更高。外来物种在乡村区溪流中的出现频率显著更高。本研究结果凸显了保护伊瓜苏河下游流域森林区的重要性：该区域拥有独特的鱼类区系，同时正面临着集约化农业开发导致栖息地丧失等多重生物多样性威胁。