Fish community structure of Juramento reservoir, Sao Francisco river basin, Minas Gerais, Brazil

Many rivers in Brazil as the Sao Francisco (SFR) have been impounded for reservoirs construction purposes. However, there is a lack of knowledge on their fish fauna in many areas, including headwaters. The present study aimed to describe the fish community structure from Juramento reservoir, located on juramento River, a branch of SFR basin. Six bimonthly samplings were made in four different sites. Gill and cast nets, beach seines and sieves were used to collect Fish. Ecological indexes as well as the relationship between fish abundance and some limnological variables were determined. 3288 fish belonging to 33 species (16.5% of the total described for SFR basin) were captured, being 75.7% Characiformes, 18.1% Siluriformes, 3% Cyprinodontiformes and 3% Gymnotiformes. Only two non-native species, 'tamboata' - Hoplosternum littorale (Hancock, 1828) and 'trairao'- Hoplias lacerdae Ribeiro, 1908 were found. The highest catches in number occurred in the dry period (March-October) and the lowest one in the wet season (November-February). Diversity was higher at Barragem station and richness did not vary between reservoir zones. Five migratory species were found downstream of the dam (four exclusively there), whereas only the'curimbata-pioa' - Prochilodus costatus Valenciennes, 1850 occurred in the reservoir. The low observed correlations between fish abundance and the limnological variables utilized suggest that the local fish fauna is not strongly affected by their variation.