WWW.WAS.ORG • WORLD AQUACULTURE • SEPTEMBER 2016 41 mg/L, ammonia concentration 0.18 ± 0.05 mg/L, nitrite concentration 0.021 ± 0.003 mg/L and pH 7.8 ± 0.4. All LRTs were harvested on day 40 by reducing water level in the tanks and scooping out postlarvae with hand nets (Fig. 3). The number of 40-d old post-larvae collected was 200,463 averaging 21.1 ± 4.3 mm total body length and 199 ± 92 mg body weight. The average survival rate of larvae was 9.3 ± 4.9 percent. Harvested post-metamorphosis fish fry were transferred to 40-t circular concrete nursing tanks and stocked at 0.5-1.0 fish/L. Fry were further grown for 55 days and fed during this period with Love Larva No. 5 (680-1058 µm) and No. 6 (1100-1300 µm) plus 1.0- and 1.6-mm feeds3. To reduce cannibalism and size variation, grading was done every four days during this period (Fig. 4). The final harvest after 55 days (95 dph) yielded 177,462 fingerlings averaging 3.2 ± 0.3 g body weight (Fig. 5). Survival during this last phase was 88.5 percent with an FCR of < 1.0. Conclusion Although spawning was successful, the hatching rate was low, suggesting insufficient nutrition of broodfish, which in turn affected embryonic development. Future attempts should focus on the proper control of broodfish nutrition. Also, the considerable mortalities observed during the first two weeks after hatching were possibly because of the shortage of appropriate amounts of small-size prey such as copepods. The quantity of copepod nauplii provided to larvae in this trial (0.03-0.06 individuals/ml) during 2-5 dph and adult copepods (0.2-0.5 individiduals/mL) during 7-14 dph was insufficient to support good growth and survival rates. In future trials, special attention should be given to improve production efficiency of copepods from shrimp ponds. In general, the survival rate achieved in this trial is encouraging and demonstrates the possibility of successful mass production of grouper fingerlings in captivity under the harsh environmental conditions of Abu Al Abyad Island (Yousif et al. 2011). Such success in orange-spotted grouper fingerling production is expected to give a boost to the emerging aquaculture sector in the UAE and also give impetus to current restocking programs aimed at natural resource conservation. Notes Omer M. Yousif, Aquaculture and Marine Studies Center, Abu Al Abyad Island, Department of the President’s Affairs, P.O. Box 372, Abu Dhabi, United Arab Emirates, Fax: 00971-2-8839112, E-mail: omeryousif@gmail.com 1 Aquafauna Bio-Marine, Inc, USA 2 Hayashikane Sangyo Co. Ltd., Japan 3 Skretting, Turkey References Abdessalaam, T.Z.A. 2002. The marine environment of Abu Al Abyad. Pages 41-55 In: R.J. Perry, editor. The Island of Abu Al Abyad. Environment Research and Wildlife Development Agency, Abu Dhabi, United Arab Emirates. Choat, J.H., S. Alam, K. Al-Khalaf, A. Al-Kulaifi and J. Burt. 2015. Epinephelus coioides. The IUCN Red List of Threatened Species. www.iucnredlist.org Grandcourt, E.M., Al Abdessalaam Zahran, F. Francis, A.T. Al Shamsi. 2005. Population biology and assessment of the orange spotted grouper, Epinephelus coioides (Hamilton, 1822), in the Southern Arabian Gulf. Fisheries Research 74:55-68. Ma, Z., H. Guo, N. Zhang and Z. Bai. 2013. State of art for larval rearing of grouper. International Journal of Aquaculture 3(13):63-72. Yousif, O.M., D.V. Minh, M.K. Kumar, A.-F.A. A.-Rahman and B.V. Hung. 2011. Spawning and larviculture trials of cobia, Rachycentron canadum (Linnaeus, 1766) in the United Arab Emirates. World Aquaculture 42(1):33-36. Yousif, O.M., M.K. Kumar, B.V. Hung, A-F.A. Ali and D.V. Minh. 2012. Spawning and larval rearing of goldlined seabream, Rhabdosargus sarba on Abu Al Abyad Island, United Arab Emirates. World Aquaculture 43(2):34-36. Yousif, O.M., M. Krishnakumar and A-F.A. Ali. 2016. Hatchery techniques of marine finfishes and shrimps at Abu Al Abyad IslandAbu Dhabi. National Archives, Abu Dhabi, United Arab Emirates. FIGURE 4. Size grading orange-spotted grouper fingerlings. FIGURE 5. Orange-spotted grouper fingerlings at 95 dph. Although spawning was successful, the hatching rate was low, suggesting insufficient nutrition of broodfish. In general, the survival rate achieved in this trial is encouraging and demonstrates the possibility of successful mass production of grouper fingerlings in captivity under the harsh environmental conditions of Abu Al Abyad Island.
RkJQdWJsaXNoZXIy MjExNDY=