Distribution of Siluriformes in a river under the influence of a small hydroelectric power plant of the Paraná River Basin, Brazil

ABSTRACT When a river is dammed, impacts differ according to distance from the dam under consideration, and sites closer to the dam are more affected than distant ones. Damming a river changes the flow and landscape characteristics, which, in turn, change the hydrological, limnological and ecological dynamics, such as biological production, species distribution, and ecosystem structuring, functioning and services. This study evaluates the distribution pattern of the Siluriformes (catfish) fish species near a small hydroelectric power plant in the Jaguariaíva River, considering three distinct distances from the dam: upstream region, reservoir and downstream region. Samples were taken with gillnets between March 2013 and December 2014. The abundance and richness of the Siluriformes species were evaluated. A permutational multivariate analysis of variance was used to access possible differences in species composition among sites. Finally, a permutational analysis of multivariate dispersion was used to assess possible differences among sampling sites and to examine composition similarities among sites. A total of 840 Siluriformes individuals were captured, distributed among ten species and four families. The highest richness was observed in the downstream region, while the lowest richness was observed in the reservoir area. Differences in the abundance of species were observed between the three distinct regions; the downstream region presented the highest species abundance (CPUE), whereas the lowest abundance was observed in the dam region. Hypostomus paulinus and Hypostomus strigaticeps were abundant species, but exclusively sampled in the downstream region, while Corydoras ehrhardti and Cambeva diabola presented their highest abundance in the upstream region. The distinct longitudinal distribution of Siluriformes observed in this study can be interpreted as indicative of the negative effects of damming. Our study suggests that building small dams may result in negative impacts on the fish assemblage, impacts comparable to those of large reservoirs in terms of spatial changes. It is fundamentally necessary to better evaluate the environmental impacts of small dams in the Neotropical region, especially because few is known about them and how such impacts are comparable to impacts of larger reservoirs.

摘要：当河流筑坝后，其影响程度随与大坝的距离发生变化，距大坝越近的位点受影响程度显著高于远端位点。筑坝会改变河流的水文情势与景观特征，进而引发水文、湖沼学及生态动态的改变，包括生物生产力、物种分布格局以及生态系统的结构、功能与服务供给。本研究以雅瓜里亚伊瓦河（Jaguariaíva River）上的小型水力发电厂周边区域为研究场景，选取距大坝的三个不同距离梯度：上游区域、库区与下游区域，评估鲇形目（Siluriformes）的物种分布格局。研究于2013年3月至2014年12月期间采用刺网开展采样工作。本研究对鲇形目物种的丰度与物种丰富度进行了评估：采用置换多元方差分析（permutational multivariate analysis of variance）检验不同采样位点间的物种组成差异；最后通过置换多元离散度分析（permutational analysis of multivariate dispersion）评估采样位点间的潜在差异，并检验各采样位点间的组成相似性。本次研究共捕获840尾鲇形目个体，隶属于4科10种。下游区域的物种丰富度最高，库区的物种丰富度最低。三个区域的物种丰度存在显著差异：下游区域的单位捕捞努力量渔获量（Catch Per Unit Effort, CPUE）最高，大坝区域的丰度最低。豹纹下口鲶（Hypostomus paulinus）与条纹下口鲶（Hypostomus strigaticeps）为优势物种，但仅在下游区域被采集到；而埃氏兵鲶（Corydoras ehrhardti）与坎贝瓦鲶（Cambeva diabola）的丰度峰值出现在上游区域。本研究观测到的鲇形目物种独特的纵向分布格局，可作为筑坝产生负面影响的佐证。本研究表明，修建小型水坝可能对鱼类群落造成负面影响，其引发的空间变化影响程度可与大型水库相媲美。鉴于目前对新热带区（Neotropical region）小型水坝的环境影响研究匮乏，且此类影响与大型水库影响的对比机制尚不明确，因此对小型水坝的环境影响开展更全面的评估具备重要的科学意义。