WWW.WAS.ORG • WORLD AQUACULTURE • DECEMBER 2024 45 Nursery Rearing Before harvesting the mullet fry from the larval rearing tanks, they were anesthetized using 20 ppm AQUI-S® to sedate them to prevent the aggressive leaping behavior. Fry were harvested using a 5 mm perforated plastic bin to avoid handling stress and they were stocked in a 15 m3 nursery tank at a density of 207 fish/m3. On the first day, fry were handfed to satiation with 0.5 mm feed (58 percent crude protein and 15 percent crude fat, Skretting, France) and afterward from the next day to the end of the rearing period they were fed at 7 percent of the total biomass with 0.5 mm and 0.8 mm (58 percent crude protein, 15 percent crude fat, Skretting, France). Fry were fed every 3 hours from 6 am to 6 pm. A 200 percent water exchange rate per day was applied in the nursery rearing tanks throughout the rearing period. Uneaten feed and feces were siphoned out every evening. The mean water quality values (±SD) recorded were: water temperature 23±1 0C, dissolved oxygen 6.5 ± 0.5 mg/L, pH 7.5±0.2, ammonia 0.5 ±0.2 mg/L and nitrite 0.3 ± 0.1 mg/L. Sampling was done biweekly and growth data are shown in Figure (3). Mullet juveniles reached an average weight of 7.09± 1.5 grams by 100 dph attaining 0.113 g weight gain per day. Survival after stocking in the nursery tanks was 80 percent (Figure 4). Summary and Conclusions Blue spot mullet collected from the wild were successfully induced to spawn in captivity and reared to the juvenile stage, but the attained larval survival was only 1.23 percent which was most probably due to the lack of proper brood stock management. The brood stock fish collected from the wild were not given enough time in the captive condition and the fish were fed on the enriched brood stock feed only for a short period before commencing the spawning trials. Extended acclimation and domestication with an appropriate nutritional regime will improve egg quality and larval survival. However, considering mullet are known to have reproductive dysfunction in captivity and are quite difficult to spawn under captive conditions, the results of this first trial on V. seheli demonstrated successful spawning of the fish is possible by hormone administration. More research and trials must be carried out in the future to find the reasons for the sudden mortality observed between 16 and 20 days of larval rearing. The suggested future trials should address refining broodstock husbandry and management, larval rearing protocols and the growth of this species under local climatic conditions. The UAE, with its focus on food security, is encouraging the development of technologies for new species of fish. Developing farming techniques of this euryhaline and detritivorous species could be a good option for aquaculture in the UAE. Acknowledgments We acknowledge gratefully the contribution and dedication of the AMSC staff and Abu Al Abyad Fishermen. References to commercial products do not constitute endorsement of those products but does imply approval to the exclusion of other products that may be suitable. Notes Omer M. Yousif*, Krishnakumar Menon, Balamurugan Vadivel, John Antony and Trig T. Ali The Aquaculture and Marine Studies Center, Abu Al Abyad, The Private Department of the President, Abu Dhabi, UAE. * Corresponding author: omar.m@dopa.ae 1 AQUI-S, https://www.aqui-s.com References IUCN (International Union for Conservation of Nature). 2012. IUCN Red List Categories and Criteria: Version 3.1, Second edition. IUCN, Gland, Switzerland and Cambridge, UK. Moorthy, K.S.V., H.R.V. Reddy and T.S. Annappaswamy. 2002. Diel feeding patterns, gastric evacuation rate and diets of the mullet, Valamugil seheli (Forskal) in Mulki Estuary, west coast of India. Asian Fisheries Sciences, 15:73-81. Ralph, G.M., E. Stump, C. Linardich, R.W. Bullock, K.E. Carpenter, D.J. Allen, C. Hilton-Taylor, R. Al Mheiri and O. Alshamsi. 2021. UAE National Red List of Marine Species: Reef-building corals, cartilaginous fishes and select bony fishes. 2021. Ministry of Climate Change and Environment, Dubai, United Arab Emirates. Saleh, M. 2008. Captured-based aquaculture of mullets in Egypt. Pages 109-126 In: A. Lovatelli and P.E. Holthus, editors. Capturebased aquaculture. Global overview. FAO Fisheries Technical Paper, No. 508. FAO, Rome, Italy. Yousif, O.M., A.A. Fatah, K. Krishna, D.V. Minh and B.V. Hung. 2010. Induced spawning and larviculture of grey mullet, Mugil cephalus (Linnaeus 1758) in the Emirate of Abu Dhabi. Aquaculture Asia Pacific 15 (1): 41-43. Yousif, O.M., M. Krishnakumar and A-F.A. Ali. 2016. Hatchery techniques of marine finfishes and shrimps at Abu Al Abyad Island-Abu Dhabi. National Archives, Abu Dhabi, United Arab Emirates. FIGURE 4. Blue spot mullet juveniles at harvest. FIGURE 3. Blue spot mullet juveniles at harvest.
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