In the Amazon region there is a lack of understanding in regards to the dynamics of mercury contamination in stream ecosystems that drain forested upland soils, and which are independent of the hydrological pulse of major rivers. This study investigated the importance of limnological aspects in relation to mercury bioaccumulation in fish species collected in September, 2009 in ten streams draining the Mamuru Arapiuns interfluvial region, part of the Mamuru river basin. Characidium sp1 presented the highest Hg concentration (515.6 ng.g-1) and Carnegiella strigata the lowest (155 ng.g-1). Hyphessobrycon sp1 was the most frequently encountered fish species in the streams studied, and dissolved oxygen and pH were the only limnological parameters that correlated positively among the streams. Most species did not present a significant relation between total Hg bioaccumulation and weight, nor as a function of standard length. In relation to the latter variable, Hyphessobrycon sp1 from Abiduina stream was the only species which showed positive accumulation of total Hg, serving as the best Hg bioindicator in the streams studied. Trophic categories for the fish species were determined in relation to feeding strategies and mean total Hg concentrations, in ascending order: herbivore (202.8 ng.g-1), carnivore (236.5 ng.g-1), omnivorore (295.8 ng.g-1), general insectivore (336.3 ng.g-1), allochthonous insectivore (347.9 ng.g-1) and autochthonous insectivore (429.2 ng.g-1). The importance of insects as a mercury transfer link from streams sediments to fish of varying trophic levels was clearly evident. Total Hg levels total found in fish from remote streams investigated in this study reinforce the theory of naturally occurring mercury in regional soils. Furthermore, the results also suggest that Hg ecotoxicology of in fish can have an influence the structure of aquatic communities.
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