IMPACTS OF FISH FARM DAMS ON TEMPORAL AND SPATIAL DISTRIBUTION OF Astyanax cf. bimaculatus IN MICROBASINS OF THE MACHADO RIVER (RONDÔNIA, BRAZIL)

The present study evaluated the effects of fish farm dams on spatial and temporal distribution of lambari Astyanax cf. bimaculatus in five headwater streams of the Machado River basin, Rondônia State, Brazil. The results show that fish farm dams are spatially separating wild lambari populations into upstream and downstream groups. Moreover, it was observed that the dry and rainy seasons influence the abundance and presence of A. cf. bimaculatus in these areas, while limnological parameters did not differ y in the streams. Additionally, it was shown that fish farm dams built in the headwater stream areas impede the migratory routes of A. bimaculatus, and also possibly the local movements of resident fish populations. Therefore, before the implementation of new farm dams using natural streams in the future, mitigation plans should include adequate access routes for fish to travel between upstream and downstream areas, in order to avoid adversely affecting their wild populations. Keywords: Fish farm dams; lambari fish; Madeira River; microbasins; population parameters.