Observations of oocyte final maturation and eggs on patin Pangasius hypophthalmus under artificial rearing conditions

摘要

Nine females of Patin, Pangasius hypophthalmus (1.3-2.9 kg) were treated with human chorionic gonadotropin (HCG). Two HCG injections (500 and 1500 IU/kg at a 14-h interval) induced oocyte final maturation for all females. Oocytes from three femaleswere continuously monitored by cannulation. The oocyte final maturation was grade I prior to hormone treatment and the fish released eggs at grade VI. Newly ovulated eggs (40-300 g) from nine females were stripped during 7 h 30 min-14 h 30 min after thesecond injection at 26.0-33.5 deg C. The number of eggs was 1423-2052 eggs/g. The mean diameter of the newly ovulated eggs of nine females ranged from 1.06-1.12 mm. The stages of egg development were observed in three females. The eggs hatched during 22h 45 min-34 h after fertilization at 26.0-30.0 deg C. The fertilization and hatching rates of nine females were 80.6+-5.0 percent and 56.8+-12.4 percent (mean+-SD), respectively. This study concludes that high fertilization and hatching rates of P. hypophthalmus can be achieved by determining the optimum timing for egg stripping by monitoring oocyte final maturation.