Migratory fish habitat fragmentation by hydropower dams: history and trends for the São Francisco and Paraíba do Sul River basins

Abstract

The maintenance of the longitudinal connectivity and natural flows of rivers are crucial for preserving the abundance and diversity of long distance migratory fish. Using a quantitative analysis based on maps, we analyze the fragmentation process of the rivers of the São Francisco River Basin (SFRB) and Paraíba do Sul River Basin (PSRB), in Brazil. In this work, we drew different scenarios for the fragmentation, quantifying this process in a historical and potential perspective taking into account the present and future state of the river basin. We also determined the probable number of migratory species in every reminiscent lotic extension. We observed the presence of a larger number of migratory species in fragments equal or larger than 100 km. On the future scenario, there was an increase in the number of fragments, especially the ones equal or shorter than 50 km, inadequate to hold most of the migratory species. In this work we show the history of hydroelectric development in the two basins and compare how these trends can affect the future sustainability of these rivers.