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 本研究对伊瓜苏河下游流域8条流域土地利用类型（林地与乡村区域）各异的溪流开展鱼类区系（fish fauna）调查，以评估其鱼类群落组成与物种丰富度。研究于2015年5月至2016年2月期间，采用电渔法（electrofishing technique）每季度开展一次鱼类采样。总计采集到4239尾鱼类个体，隶属于6目、11科、26种。鲇形目（Siluriformes）和脂鲤目（Characiformes），以及脂鲤科（Characidae）和毛鼻鲶科（Trichomycteridae）为物种最为丰富的类群。在所采集的全部物种中，65%为伊瓜苏河下游流域特有种，另有4个物种尚未被正式描述，4个为外来物种。正如伊瓜苏河流域的典型特征，本次调查的鱼类区系呈现出物种丰富度较低、特有性较高的特点，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之中。本次记录的物种仅占该流域已记录的106个物种的24.5%。不同溪流的鱼类区系存在显著差异，仅双带丽脂鲤（Astyanax bifasciatus）和斯塔氏毛鼻鲶（Trichomycterus stawiarski）这两个物种同时出现在林地和乡村溪流中。此外，位于保护地内的溪流物种丰富度更高。乡村溪流中外来物种的出现频率更高。本研究结果凸显了保护伊瓜苏河下游流域林地的重要性——该区域拥有独特的鱼类区系，同时正面临着集约化农业导致的栖息地丧失等多重生物多样性威胁。