Estrutura trófica das assembléias de peixes em biótopo de herbáceas aquáticas nos rios Araguaia (Tocantins) e Trombetas (Pará), Brasil.

Abstract

This study aimed to perform a characterization and a comparison of the trophic structure of fish assemblages in aquatic herbaceous stands between Araguaia and Trombetas rivers and among different phases of hydrological cycle. A total of 125 fish species were collected in the Araguaia River and 94 in the Trombetas River. The fish assemblage composition analysis revealed that Araguaia and Trombetas rivers have somewhat dissimilar faunas, and that temporal variation was more significant in Trombetas than in Araguaia River. Taxonomic differences were attributed to the low connectivity of the studied rivers, whereas temporal variation in the assemblage composition were related to environmental peculiarities influencing herbaceous plant and the fish assemblages. The ordination analysis revealed that trophic structure wasn t very similar between rivers. Fish assemblages in Araguaia s herbaceous plant stands showed a higher number of trophic categories, higher number of elements trophics in food webs, total number of links, linkage density, and lower temporal variation. In Trombetas river the fish assemblages presented a pronounced temporal variation with lower numbers of trophic categories, lower number of elements trophics in food webs, total number of links, linkage density, except during the falling season, in which the trophic structure and food webs are more similar to those of Araguaia River. Differences in trophic structure were suggested to result from peculiarities of the two river systems, which influence the availability of resources, and other local conditions related to the structure of aquatic herbaceous biotopes in each river.