The Cupari River is the main tributary of the right margin of the lower Tapajós River,
which are planned deployments of 13 Small Hydroelectric Plants (SHP). This study aimed to
investigate environmental factors that may influence the structure of fish assemblages in Cupari
River and analyze the efficiency of two methods of fish sampling. Sampling of fish and
environmental variables were realized in 11 sampling points in the months of December 2014
(low water) and May 2015 (high water), using gillnet and manual traction seine. Were collected
3.273 specimens, representing 144 species, distributed in 80 genus, 34 families and nine order.
The most abundant species were Moenkhausia aff. ceros, Rhinopetitia potamorhachia and
Knodus sp. 1. There was not statistically significant difference in species composition between
sampling periods. The abundance was positively correlated to temperature. The richness and
diversity were positively correlated with dissolved oxygen. The dominance was negatively
correlated with dissolved oxygen. The distance of sampling points for the mouth of Cupari
River and altitude did not affect significantly the values of the ecological descriptors. Three
species were recognized as new and were recorded two endangered. There was significant
difference in composition, richness and abundance of species caught by different methods. The
results are of relevance for the conservation and allow the proposition of management measures
for ichthyofaunistic resources in Cupari River.
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