ALTERAÇÕES TEMPORAIS SOBRE A ESTRUTURA FUNCIONAL DAS ASSEMBLEIAS DE PEIXES DURANTE ONZE ANOS DE FORMAÇÃO DE UM RESERVATÓRIO DO MÉDIO RIO TOCANTINS, BRASIL

Abstract

The damming of rivers for the construction of hydroelectric dams represents an important generator of environmental impact in the aquatic ecosystem, affecting the composition and the diversity of the fish fauna. This work aims to evaluate the temporal changes in the functional structure of fish assemblages in the Tocantins River before and after the construction of the Lajeado dam. Were used fourteen functional attributes measured from the fauna of fish collected with gillnet during eleven hydrological periods. Functional attributes related to size, body size, habitat use and reproductive strategy were more sensitive to the formation of fifteen functional groups. In general, there was an increase in the abundance of all groups after the reservoir, with more occurrence of small species, fusiform or compressed body and pelagic or benthopelagic habitat. Demersal habitat species, long-distance migrators and body size large were the most affected by the reservoir, with a strong reduction of abundance (less than 1% of the total). The analysis based on the construction of functional groups helps to identify the traits that are more sensitive to the new condition imposed by the reservoirs. So that the upstream area, of lotic nature, are recognized the priority conservation areas and free of new hydroelectric projects, in order to ensure the survival of species that share the most sensitive traits. Keywords: Tocantins River; reservoirs; environmental impact; neotropical fish; functional diversity.