Avaliação da atividade reprodutiva da comunidade de peixes dos primeiros quilômetros a jusante do reservatório de Itaipu

Abstract

The limnological and hydrological pulses instability io rivers controlled by dams may have serious cousequences oo reproduction in fish with adverse implications on fishery productioo of the basin. This paper deals with the reproductive activity of species inhabiting the first kilometers of the Paraná River, downstream from Itaipu Dam, during the period from April, 1991 to March, 1992. Comparisons were made between this result and that 1986-87 period. Gill nets and longline were used at a 24-hour/month effort. Indicators on reproductive activity were based on frequency of individuals in reproduction and on gonadosomatic relationship. The results showed a decrease in reproductive activity, for the latter period and was restrictecd to small fish. Although presenting gonad development, the big migratory species did not spawn and showed extensive ovarian atresy process. Artificial structures that favour complementation of gonadal maturation and spawning are considered important to the conservation of fish populations.