O papel de ribeirões para a manutenção da diversidade de peixes no Alto São Francisco

Abstract

In the tropical region, among the lotic freshwater ecosystems, the intermediate-sized rivers are little known compared to headwaters and large rivers. They seem to play a crucial role in the life cycle of migratory fishes and possibly harbor an important part of the fish community in their basin. However, few studies have investigated these matters for different river sizes and recent publications are absent. Therefore, this study aimed to assess if the river size influences the juveniles of migratory species (chapter one) and the diversity patterns (alpha and beta diversities) of the region along rivers of different sizes (chapter two). Fish communities from 16 and 48 rivers were analyzed for chapters one and two, respectively, in the upper São Francisco River basin. The results showed that smaller rivers, especially when draining regions close to floodplains, seem to be the first places where juveniles of migratory species move after leaving the floodplain lagoons. Information indicating that individuals gradually move towards larger rivers as they grow were also raised. The analyzed rivers showed high values for alpha and beta diversities, with turnover being the main process leading to species variation among the rivers of all sizes. The alpha diversity showed an increase with the size of the river while the beta diversity does not seem to have a clear pattern related to the river size. 34 additional species from lotic stretches that had not been registered yet for this region were added and it was shown that several additional species can still be recorded. This study concluded that intermediate-sized rivers, despite little studied, are essential in maintaining biodiversity of the entire basin, including for large species, such as migratory.