Population structure, condition factor and reproductive period of Astyanax paranae (Eigenmann, 1914) (Osteichthyes: Characidae) in a small and old Brazilian reservoir

Abstract

The population structure, condition and reproductive period of Astyanax paranae adult individuals inhabiting a small reservoir were investigated. The fishes were quarterly captured from the riverine and lacustrine zones of the Alagados Reservoir, Paraná, Brazil, during 1996/1997 and 1998/1999. The sex ratio differed from 1:1 with the predominance of the females in all standard length classes and total population sample. The females showed higher condition than the males. Both the sexes presented lower mean condition values in April and higher mean condition values in July. The estimated values of the regression coefficient indicated isometric growth for the females and males. The gonadosomatic relationship reached a maximum value of 14.80% for the females and 8.43% for the males. The reproductive period possibly occurred from October to April.