The objective of this study was to induce spawning in pirapitinga-do-sul, Brycon opalinus, with the application of hormones and to determine the pattern of oocyte diameter frequency distribution in females prepared to induction. One hundred and twenty spawners with 25.5 to 32.0 cm of length were placed in circular ponds of 10 m of diameter, at Estação de Aqüicultura de Paraibuna-SP of CESP. In order to determine the females apt to reproduction, samples of oocytes were obtained with plastic catheter and analysed. These oocytes were valued by colour, size, position of nucleus and oocyte diameter percentual frequency distribution. The males were selected by quality of semen. Twenty-nine females were selected and received two injections of SPE (salmon pituitary extract): the first, of 5 mg/kg and the other, of 10 mg/kg, with 12 hours of interval. The males that showed 90% of spermatic motility and 85% of life spermatozoa were selected and received 5 IU/g of hCG (human chorionic gonadotropin) when the females received the second dose. The oocytes of the 14 females that responded to the hormone treatment were gray or wine in colour, and in the females that presented high rates of fertilization, the oocyte diameter percentual frequency distribution showed mode of 1,900 mm. The average rate of fertilization was of 90% and that of hatching was 40%.
fish; Brycon opalinus; pirapitinga-do-sul; induced spawning
