Fish distribution in a basin affected by damming: spatial and local effects shaping fish assemblages in streams and reservoir

Abstract

The impacts of hydroelectric reservoirs on fish assemblages can be influenced by several local and spatial factors. In addition to the biotic changes caused by the formation of the reservoir itself, other water bodies in the basin, such as streams, can also be affected by damming. The main goal of this study is to investigate the structure and distribution of fish assemblages in the UHE FURNAS reservoir and its tributary streams. In the chapter 1 we assesses how native and non-native assemblages respond to the effects of distance from the dam and local variables related to water quality and physical habitat. The aim of chapter 2 was identify, on streams, the role of connectivity (measured by distance to the reservoir) and local and regional disturbance indices on the occurrence of non-native species and their shared richness with the reservoir. Data were collected at 40 sites along the reservoir's shoreline and at 40 streams within the corresponding drainage basin. In the reservoir, distance from the dam was the main explanatory variable for species richness and abundance. For native species, both richness and abundance decreased towards to the dam. A similar pattern was observed for the abundance of non-native species. In the streams, local impacts increased the probability of non-native species occurrence and shared richness, regardless of distance from the reservoir. This highlights the importance of incorporating local and spatial variables in studies of reservoir’s ichthyofauna, as well as considering the dynamics of streams and reservoirs in an integrated manner.