PROGRESS IN CONTROLLED BREEDING OF NASSAU GROUPER (EPINEPHELUS-STRIATUS) BROODSTOCK BY HORMONE INDUCTION

Human chorionic gonadotropin (HCG), luteinizing hormone-releasing horm one analogue (LHRH-a), and carp pituitary homogenate (CPH), used alone or in various combinations, were tested as spawning agents in captive E. striatus broodstock. Fifty hormone-induced strip-spawning trials w ere attempted using a two-injection sequence in which:a priming dose ( PD) was followed 24 h later by a resolving dose (RD). Hormone treatmen t strategies tested included, HCG alone (PD-1000 IU kg(-1) bw, RD = 50 0 IU kg(-1) bw), LHRH-a alone (PP = 50-100 mu g kg(-1) bw, RD = 100-20 0 mu g kg(-1) bw), HCG (500 IU kg(-1) bw) in combination with LHRH-a-( 50-100 pg kg(-1) bw) as priming or resolving doses, and CPH (PD = 10 m g kg(-1) bw) in combination with LHRH-a (RD = 50-100 mu g kg(-1) bw). As an alternative to hormone injection, intramuscular implantation of a cholesterol pellet containing LHRH-a (200-250 mu g) was tested in tw o females. Females with mean oocyte diameters ranging from 482 to 561 mu m were suitable for hormone-induced spawning. Oocyte diameter incre ased to 524-708 pm within 24 h of the priming dose and to 852-945 pm w ithin 9-16.4 h following the resolving dose. Average diameter of spawn ed (water hardened) eggs ranged:from 879-978 mu m. Although fertilizat ion rate (0-94.7%) varied widely, among trials, successful Spawnings(f ertilization rate greater than or equal to 50%) were obtained in all-o f the hormone, strategies tested. Use of different hormones in combina tion showed no advantage over a single-hormone strategy. As HCG appear ed to cause an immune response, LHRH-a is recommended for repeated app lication. Implantation of LHRH-a produced variable results, inducing o vulation in one female, but apparently inducing sex reversal other.