1997 Volume 45 Issue 1 Pages 67-73
The changes in ovarian development during final oocyte maturation and ovulation induced by different hormonal treatments in cultured tiger puffer Takifugu rubripes were monitored by ovarian biopsy. Single implantation of LHRH-a (des-G1y10 [D-Ala6] -LHRH ethylamide) cholesterol pellet (LHRH-a 400, μg/kg) or osmotic pump (LHRH-a 50 μg/day/fish for 2 weeks) successfully induced ovarian maturation and ovulation in three-year-old cultured tiger puffer with yolk-laden oocytes. Repeated injections of HCG (500 IU/kg) combined with chum salmon pituitary (SP) homogenate (7 mg/kg) every 5 days also induced ovarian maturation and ovulation. Overall, the mean time span from the beginning of hormonal treatment of fish with initial oocyte size between 800 and 900 μm in diameter to ovulation was 18.8 days. In contrast, the mean time span in fish with initial oocyte size over 900μm in diameter was 10.6 days. Oocytes in the control fish receiving no hormones did not develop and became atretic. The results obtained indicate that a single implantation of LHRH-a cholesterol pellet is efficient for inducing maturation and ovulation of cultured tiger puffer. Also, the monitoring of initial oocyte diameter by ovarian biopsy was found to be important for achieving synchronous spawning of several fish.
