Efeito de bacias e de variáveis ambientais na estrutura de comunidades de peixes de igarapés na região do interflúvio Madeira-Purus

Abstract

The main objective of this study was to investigate the richness and composition of the fish fauna in headwaters of streams in the Madeira-Purus interfluvial region, and if they are related to environmental variables and / or watersheds. Data was collected along two field campaigns, lasting approximately 20 days each, between the months of April and July 2007. A total of 22 streams were sampled, belonging to five different watersheds. Fish were captured with hand nets and small seine nets. Information on the structural characteristics of the streams and physical-chemical of water was also obtained. A total of 5509 fish were captured, belonging to 86 species, 22 families and six orders. Characiformes was the most diversified taxonomic group, followed by Gymnotiformes and Siluriformes. The species composition was influenced mostly by the width and depth of the channel, discharge and substrate. The presence of different environments around creeks has also contributed to the differences in fish species composition. The watersheds had strong effect on communities of fish. However, the results cannot allow to assert with certainty if differences in fish composition among watersheds are reflecting historical effects or environmental conditions.