Spawning Red Drum Sciaenops ocelatus, and evaluation og egg quality.

H. GRIER, F. MEIJIDE, JACK MORRIS

San Diego, USA

Congreso; Aquaculture America 2002; 2002

America Society of Aquaculture

The red drum, Sciaenops ocellatus, can be induced to spawn naturally by photothermal rooms. A change in photoperiod from late winter to early fall conditions (14 hrs L and 10 hrs D to 10 hrs L and 14 hrs D), with temperature fluctuations to simulate fall conditions (24 oC to28oC), will induce the fish to become reproductive and spawn naturally in photothermal rooms.  Once spawning commences, it is not unusual to have fish spawn on a daily basis. Broodstock were maintained as individual females with two males in twelve feet diameter fiberglass tanks with biofilters. They were placed in the photothermal rooms on October 5, after conditioning in outdoor ponds. The first spawn occurred on October 7. Of the seven females so maintained, three did not spawn naturally and were subsequently implanted with time-release pellets containing 150 mgm of salmon gonadotropin-releasing hormone (Ovaplant, Syndel International, Inc.). After implant, all of the fish spawned the following day. An egg collector, powered by an airlift, removed floating eggs from the water surface and into a collecting net.   Three methods were used to determine egg quality: percent fertilization, percent hatch, percent survival to first feeding following the methods of Neidig et. al. 2000 (N. Amer. J. Aquacult. 62:103-113). In all, a total of 46 spawns were obtained, eight of them were from hormone-induced fish. Percent fertilization, in all but five spawns, was above 98%, and no differences were observed between natural and hormone-induced spawns. Percent hatch was above 85% in all but 17 spawns, ranging from 43.8 to 97.7%; five of nine hormone-induced spawns were below 90% hatch. Survival to first feeding ranged between 4% and 95%. We strongly suspect that the lower survival values may have been due to the presence of the pathogenic bacterium Vibrio harveyi, a ubiquitous pathogen in salt water culture systems. Further work is required to determine if this is true. Good egg quality has been achieved with hormone implants in this study; it is also indicated that reproductive broodstock can be triggered to spawn on demand using hormone implants.