Observations of Oocyte Final Maturation and Eggs on Patin Pangasius hypophthalmus under Artificial Rearing Conditions.

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Nine females of Patin, <I>Pangasius hypophthalmus</I> (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 females were 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 the second injection at 26.0-33.5°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 22 h 45 min-34 h after fertilization at 26.0-30.0°C. The fertilization and hatching rates of nine females were 80.6±5.0% and 56.8±12.4% (mean±SD), respectively. This study concludes that high fertilization and hatching rates of <I>P. hypophthalmus</I> can be achieved by determining the optimum timing for egg stripping by monitoring oocyte final maturation.
日本水産増殖学会の論文