Padrões de dominância e raridade da assembléia de peixes ao longo de gradientes espaciais no reservatório de Itaipu, Estado do Paraná, Brasil

Abstract

Patterns of dominance and rarity of fish assemblage in the Itaipu Reservoir were evaluated and related to a longitudinal or river-dam gradient (composed of riverine, transitional and lacustrine zones) and to a transversal or upstream-downstream gradients of the tributaries (composed of lotic and lentic stretches of tributaries and reservoir shores). Thirteen sampling stations were sampled quarterly during 2 years. Patterns of species dominance were investigated using Whittaker plots and patterns of rarity using analysis of variance. A total of 85 fish species were caught. In the reservoir shores of riverine zone, the dominant species was the migratory Prochilodontidae curimba Prochilodus lineatus that uses the upstream floodplain as a spawning and nursery area. In the reservoir shores of transitional and lacustrine zones (i.e. close to the dam) the dominant species was the introduced Sciaenidae curvina Plagioscion squamosissimus . Loricarids dominated the tributaries. The proportion of rare species presented significant differences along longitudinal gradient. Lowest proportion of rare species was found close to the dam indicating a loss of ecological integrity in this zone