Spatial and environmental factors predict the composition of non-native fish assemblages in Neotropical reservoirs

Abstract

Hydropower dams are one of the largest sources of anthropogenic impacts on freshwater systems in the world. In addition to the modifications in environmental dynamics (i.e., fish migration barrier, water flow reduction, depth increase, flood regulation), the novel environments are favorable to the dissemination of non-native species in the basin. The lack of native species adapted to the changed environment creates occupations opportunity (i.e., available resources) for non-native species, which end up finding in these environments ideal areas to complete their life cycle. Thus, the aim of the work was identify which reservoir characteristics provide as well benefits for non-native fish species. Specifically, we tested the hypothesis that the spatial structure, reservoir productivity and morphology, and chronological characteristics are factors related to the composition and abundance of non-native fish species in reservoir. Using novel statistical techniques (Principal coordinates of neighbour matrices and Distance-based linear models), it was possible to identify the spatial patterns and to understand how the characteristics of the reservoirs influence the composition of the abundance of these species. Our results show that some reservoir characteristics provide benefits to non-native fish species, thus being localities within the hydrologic basins that can be considered as sources of non-native fish species propagules. In general, our results showed that larger and older reservoirs have a greater abundance of non-native fish species. Also, it was possible to identify spatial patterns, where in smaller scales neighboring reservoir tend to be more similar as to the composition and abundances of non-native fish species and this similarity can reach basin level.