Composição, riqueza e diversidade de peixes de igarapés no plató bacaba, flona de saracá-taquera, município de Oriximiná (Pa)

Abstract

The Amazon basin is the largest river basin in terms of fish species richness in the world, however, ichthyological studies focus on large rivers and species of commercial interest, which often exclude smaller habitats such as igarapés. The present study investigated the structure of the ichthyocenosis in the lowland igarapés of the Bacaba Plateau, tributaries of the Trombetas River. The specimens were captured using traditional collection methods that included sieves and trawls. A total of 552 specimens representing 33 species were captured, distributed in ten families and six orders. The most diverse and abundant order in both phases (flood and dry) was Characiformes, followed by Perciformes. One of these species is probably new to science and belongs to the genus Pyrrhulina. The total richness rarefaction curve did not reach the asymptote, however, this was reached by the curve of the families Cichlida and Lebiasinidae. From the ANOVA test (gl=l; n=8 p=0, 01; f = 4.208) it can be concluded that the composition of the ichthyofauna suffers strong influences of the annual variation of the waters and the abundance of species presents tendency to variations in function of the volume of water in the streams resulting from rains. The four collection stations studied did not present environmental differences. The composition found is in accordance with the composition pattern for neotropical streams. Variations in composition and richness between seasons are probably related to the intensification of biotic interactions especially in the dry season.