The Amazon is the largest and most diverse rainforest in the world. It is estimated to be home to at least 40,000 species of vertebrates alone, of which about 3,000 are freshwater fish. Despite the high diversity, much of the ichthyofauna remains unknown. Aiming to fill part of this gap, this work proposed to analyze the ichthyofauna of the Juruti region, as well as to assemble a taxonomic list and provide data for the incrementation of Amazonian knowledge. Juruti is located in the extreme west of Pará. Its vegetation is characterized by lowland and submontane ombrophilous forest formations in the plateau and slope regions, and alluvial forests in the coastal zone. Its climate is Am, according to the Kêippen classification, with few climatic variations and a rainfall index equal to 2,000 mm/year. The methodology used for the capture of specimens was: 200 throws of sieve and rapiché, 50 drags, and 5 matapis, arranged at least 1.5 m apart, for 20 h. The biological material was fixed in 10% formaldehyde solution, sorted and preserved in 70% alcohol and inserted in the scientific collection of MPEG. Collections were made in six different streams of the region, in four different hydrological periods, in the years 2006, 2007 and 2008. For the ecological analyses, the Shannon-Wiener (H') and Pielou (U) diversity indices were applied, and species richness was estimated by the jackknife estimator 1. 23,248 specimens were captured, distributed in seven orders, 26 families, 83 species and 78 morphospecies. As for the diversity indices, the dry-full period (February/2008) had the highest value H = 4.58 nets/ind. U= 0.9, in contrast to the drought (December/2006), where H'= 4.3 nets/ind.and U= 0.8. As for the richness estimate, it was calculated that the region has about 196 species of fish alone.
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