Reproductive biology of females of cachara, Pseudoplatystoma fasciatum (Teleostei, Siluriformes, Pimelodidae), kept in captivity

Abstract

The present work was developed in the Polo Regional de Desenvolvimento Sustentável dos Agronegócios do Vale do Ribeira - APTA, in the city of Pariquera-Açu, São Paulo state, Brazil, during January 1999 to June 2001. Four months old alevins were distributed in four 600 m²- earthen fishponds, at the ratio of 1,0 fish/2 m². Four stages of ovarian maturation were established: Young, Resting, Maturation, and Regression, based on the macrocospic features and bimonthly average values of the gonadosomatic (GSI), hepatosomatic (HSI), viscerosomatic (VSI) and celomatic fat (GCI) indices. The time and the average length of the first ovarian maturation were also determined. The bimonthly values of VSI, HSI and GCI per stage of maturation indicated an inverse variation in relation to the average values of GSI, with the highest ones in stages Young and Resting females, and the lowest ones, in the end of Maturation and beginning of Regression. During the reproductive cycle, the variation of these indices was discrete and the lowest values occurred in January-February. The reproductive period of this species occurs, in conditions of captivity, from the end of November to February, coinciding with the highest values of water temperature (30.0 - 32.8°C). The value of the standard average length in which 50% of the females reached the first maturation (L₅₀) was 37.65 cm.