Through an ecomorphological study it is possible to describe possible feeding and environmental tactics of each species (position in relation to the water column, distance from shores and environments), assuming that morphological variation leads to functional and performance differences, which result in differences in resource use. Thus, the objective of this study was to analyze the spatial distribution of the fish community of the Caxiuanã National Forest - PA, based on ecomorphological measurements of the 28 most dominant species. The Caxiuanã National Forest is located in the lower portion of the Anapu River, between the Tocantins and Xingu Rivers, in the Eastern Amazon, in the municipalities of Melgaço and Portei (Pará State). Collections were carried out between the months of March/April (flood) and October/November 2004 (drought), by means of experimental collecting with a waiting net. In the laboratory, ten adult individuals of each species had 18 morphological measurements taken to calculate 15 ecomorphological attributes. The data analysis was composed by ordination techniques (Principal Component Analysis) and hierarchical cluster analysis (Cluster). The result of the ordination analysis using the first two components explained 97.78% of the variation among species. The cluster analysis showed the formation of six groups, and that regardless of taxonomic proximity, it does not segregate or integrate species by environment, but rather where the species will be inserted in the microhabitats of rivers and bays of the Caxiuanã National Forest. This probably occurs due to the morphological characteristics of the species and the waterways of this region, where the separation of lentic and lotic environment is hardly perceived, because the region is a "river ría", creating an extremely heterogeneous mosaic, making studies necessary to better understand the adaptations that over time selected the species.
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