World Aquaculture Magazine - September 2021

WWW.WA S .ORG • WORLD AQUACULTURE • SEP TEMBER 2021 27 paves the way for the development of responsible, scientifically sound restocking programs for the conservation of this magnificent fish in Colombia and elsewhere. Larval Rearing The 2 DPH larvae were transferred to the CEINER facilities in Rosario Islands in 30-L bags with filtered seawater and dissolved oxygen at 25 mg/L. These larvae were stocked in a 7,000 L fiberglass larval rearing tank with filtered seawater and aeration. An initial acclimatization process of the bags with larvae was carried out until the temperature of the tank water equalized with that of the water in bags. This was a simple and efficient transfer process. Live microalgae ( Nanochloropsis and Isochrysis ) were supplied at approximately 2×10 6 cells/mL. From 3 DPH to 31 DPH, larvae (Fig. 11) were fed enriched small-strain rotifers Brachionus rotundiformis three to four times a day at densities varying from 2 to 60 rotifers/mL, according to development of the larvae. Artemia nauplii were provided as live feed to the larvae beginning at 14 DPH. Live enriched Artemia overlapped with wild plankton. Weaning was carried out by overlapping live feeds with frozen minced penaeid shrimp once a day to satiation. At 55 DPH, metamorphosis was complete and fingerlings were ready for the pre-growing stage (Fig. 12). They continued to be fed minced frozen shrimp through the juvenile stage. Rocks were placed at the bottom of the tank as substrate to provide shelter and protection. Larval development and metamorphosis and juvenile stages are shown in Figures 9-12. Currently, induced spawning and larval rearing events are being conducted in Colombia with 400,000 larvae at first feeding stage at 3 DPH. Spawnings have been successfully obtained with the methods described (LHRH-a implants at 75-100 µg/kg body weight and egg collection 42 hours after pellet implant), and larval rearing is being conducted using live microalgae and small-strain rotifers as summarized here. The intent and drive are to improve survival (to date still in the low single digits) and produce a large number of fingerlings to further develop these activities with the goliath grouper in Colombia. Outlook Mariculture has been recognized as a having high potential in Colombia and several other Latin American countries. Several species of Serranidae are among the best candidate species for aquaculture development in the region. They are hardy, have an established demand at high prices in the market, adapt very well to captive conditions, are euryhaline and suitable for nursery and grow-out in ponds and cages in the ocean and in estuaries. Colombia has well-established aquaculture infrastructure and logistics, particularly for commercial tilapia culture. The need for diversification has been identified and the goliath grouper represents a species with great potential for commercial aquaculture and restocking of the natural populations that have been depleted in the last decades. As reported in this article, artificial propagation of the goliath grouper has been proven to be experimentally and technically feasible in recent years. The results reported were obtained after several years of continuing joint efforts pursuing reproduction and ( C O N T I N U E D O N P A G E 2 8 ) FIGURE 8. Tanks (1 m 3 ) for incubation of fertilized eggs and embryos. FIGURE 9. Embryonic development of goliath grouper: 8-cell stage (top), advanced notochord stage (middle), at hatching (bottom).