Efeitos do assoreamento sobre as comunidades de peixes de igarapés da bacia do Rio Urucu, Coari, Amazonas, Brasil.

Abstract

The siltation and the soil use effects on the fish assemblages were evaluated in Província Petrolífera de Urucu streams, between the months of September and December of 2004. The fish were collected in open water and in litter benches located in meanders. Fishnests, dipnets (rapiché) and traps were utilized to sample 27 streams with a total of 108 collection. The Siltation Index (IA) and the Total Sedments in Suspension (TSS) content were utilized to quantify the degree of stream siltation. To estimate the Anthropic Area (AA) percentage, images of satellite LANDSAT -7, sensor ETM were classified. Limnological variables were also estimated, which included pH, conductivity, temperature, and dissolved oxygen; morphometric variables that weremeasured included stream width, stream depth, medium current speed, outflow and canopy opening. A total of 2.228 fish were collected that were distributed in 71 species, 5 orders and 20 families. Characiformes constituted the largest, most diverse and most abundant group, representing 82,9% of the total number of fishes collected. Hemigrammus belottii and Hyphessobrycon copellandi were the most abundant species, both in the interior base streams and in the control streams. The IA did not influence the fish assemblages when analyzed independently; however, when associated with pH and conductivity, it exerted influence on the diversity and on the dominant species. The MPS, when associated with current speed, depth, width, AD and outflow, appeared to significantly influence fish species composition. Althought the AA percentages did not present an influence on the IA, they were correlated with TSS quantities in the streams.