Changes in diet of a neotropical cichlid in response to river damming

Changes in diet of Laetacara araguaiae Ottoni and Costa, 2009 were evaluated in the Sucuriú River (Upper Paraná basin, Brazil) in an area with a small hydroelectric power plant, both before and after the formation of the reservoir, in order to answer: Did the construction of the reservoir affected the diet of this species? The results showed greater change of diet composition in the upstream section of the reservoir. It was observed that before the formation of the reservoir and the first year after, the individuals from upstream section formed a group characterized by an insectivorous diet. With the dam construction and habitat change we observed that aquatic plant material, sediment, and algae predominated in the diet. These results show the opportunistic feeding habit of L. araguaiae and contribute to the understanding of how the impoundment of rivers can influence the trophic dynamics of the ichthyofauna.

Registro de ocorrência de duas espécies de potamotrigonídeos na região do Alto Rio Paraná e algumas considerações sobre sua biologia / Occurrence record of two potamotrigonids species in the Upper Paraná River and some aspects about their biology

A distribuição geográfica das raias da família Potamotrygonidae é restrita aos principais sistemas fluviais da América do Sul. No Brasil, a ocorrência de potamotrigonídeos é conhecida em toda a Bacia Amazônica, em alguns rios da região Nordeste e na Bacia Paraguai-Paraná. O alto curso do Rio Paraná, separado no passado dos trechos médio e baixo pelas Cachoeiras de Sete-Quedas, hoje está conectado a essas áreas devido ao represamento de grande parte de seu curso. A construção das barragens destruiu obstáculos naturais, possibilitando a dispersão de diversas espécies de organismos aquáticos rumo ao alto curso do Rio Paraná. Reportamos aqui o registro da ocorrência de duas espécies de raias no Alto Rio Paraná, as quais não faziam parte da fauna nativa da região há pouco mais de duas décadas atrás.

The freshwater stingrays of the Potamotrygonidae family are elasmobranchs restricted to the major river systems of South America. In Brazil, the occurrence of potamotrigonids is known in all the Amazonian Basin, some rivers of the Northeastern region and in the Paraguay-Paraná Basin. The upper course of the Paraná River, separated in the past from the medium and low courses by Sete-Quedas Waterfalls, today is connected to these areas due to the dams constructed in great part of its course. The dams had destroyed natural barriers, making possible the dispersion of many species of aquatic organisms to the headwaters of the Paraná River. We report the occurrence record of two species of stingrays in the Upper Paraná River, which were not part of native fauna about two decades ago.