Induced Gonadal Development and Spawning of Immature Red Sea Bream Pagrus major with LHRH-a Administration in Different Ways during Winter Season

The response of sexually regressed red sea bream Pagrus major to LHRH-a (des Gly₁₀-[D-Ala₆] LHRH ethylamide) was investigated during the non-spawning season, from November to December. Fifty-five fish were divided into five groups and the following treatments were accomplished: initial and final controls (not treated), LHRH-a 200 fig cholesterol pellet (group CP200), LHRH-a 1 μg/day osmotic pump (group OP1), and LHRH-a 5μg/day osmotic pump (group OPS). In all females in the three experimental groups, gonadal maturation and spawning were induced 12 to 14 days after implantation. The cumulative amounts of LHRH-a released from each mold during the period from pellet or pump implantation were about 11 fig (CP200), 14 μg (OP1), and 60 fig (OP5), respectively. These results suggest that all treatments of LHRH-a were found to be equipotent in inducing red sea bream females to mature and spawn. It seems that the amounts of sustaining release of LHRH-a from LHRH-a 200 fig cholesterol pellet are enough to induce ovarian maturation, and a higher dosage of LHRH-a is not necessary. On the contrary, every treatment of LHRH-a showed insufficient effects on testicular maturation, and the possible cause was discussed. The results of the present study may be used as a basis for producing eggs and fingerlings all year round.