Several factors lead to the deterioration of water quality and destruction of aquatic environments, exerting a profound and negative influence on the structure of fish communities. In this work, the existence of changes in physical and chemical parameters of water, diversity and composition of the fish fauna, resulting from the silting of streams, was investigated in a campinarana vegetational complex in Northwestern Acre State, Brazil. In order to perform the assessments, two stretches of 50 meters were selected from each stream; one with and the other without sedimentation. No significant differences were found in the physical and chemical parameters between silted and non-silted samples. Samples taken from streams influenced by sedimentation showed higher species richness and diversity of fishes than non-silted streams. In addition, a psammophilous species was found as an indicator in silted streams, whereas a bento-pelagic species was an indicator in non-silted streams. Results show the importance to analyse fish community attributes in evaluating the processes of degradation of the aquatic environment by human activities.