58 SEPTEMBER 2017 • WORLD AQUACULTURE • WWW.WAS.ORG nitrification and through an intensive degradation of organic waste components. • Vertical substrate adsorbs organic matter and reduces its sedimentation. In suspended biofloc systems, vigorous water mixing and effective drainage is needed to control organic matter accumulation on the pond bottom. • Both recycle feed in the pond and provide natural food sources to cultured fish or shrimp. • Suspended bioflocs are harvested through filtration of particles. Biofilm on the vertical substrate is harvested by surface grazing. This could affect selection of the proper system for production of different fish or shrimp species. • There is an accumulating body of research on the increased immunity, pathogen elimination and probiotic effects of bioflocs (Browdy et al. 2014). This may also be the case for biofilm attached to vertical substrates. • Both systems, based on zero water exchange, are environmentally friendly. The specific system described here offers a clear advantage as an intermediate step to family farmers seeking to adopt more intensive production practices. The system allows for the use of a moderate stocking density, gradual introduction of pond lining and aeration, less vulnerability to failure of the aeration system and gradual adoption of more sophisticated technologies and practices. After gaining experience with fixed biofilm systems for a period, farmers may then choose to evaluate the suspended BFT system. It must be clearly emphasized that the work presented here is still in an initial stage of development and is largely based on observations and farm trials. This work needs to be continued and elaborated. Acknowledgments We devote this paper to the memory of Professor M.C. Nandeesha (1.7.1957-27.11.2012). Prof. Nandeesha, our friend, devoted his research, teaching and life to help and promote family farmers in India and elsewhere. His enthusiasm inspired us in doing the present research and development work. Notes Boriah Suryakumar, Hitide Seafarms, Tamil Nadu, India and Yoram Avnimelech, Technion, Israel Inst. Of Technology, Haifa Israel, agyoram@technion.ac.il References Assaduzzaman, M, M.M. Rahman, M.E. Azim, M. Ashraful Islam, M.A. Wahab, M.C.J. Verdegem and J.A.J. Verret. 2010. Effects of C/N ratio and substrate addition on natural food communities in freshwater prawn monoculture ponds. Aquaculture 306:127-136. Avnimelech Y. and G. Ritvo. 2003. Shrimp and fish pond soils: Processes and management.Aquaculture 220:549-567 Avnimelech, Y., M.C.J. Verdegem, M. Kurup and P. Keshavanath. 2008. Sustainable land based aquaculture: Rational utilization of water. Land and feed resources Mediterranean Aquaculture Journal 1:45-55 Avnimelech, Y., B. Weber, B. Hepher, A. Milstein and M. Zorn. 1986. Studies in circulated fish ponds: Organic matter recycling and nitrogen transformation. Aquaculture and Fisheries Management. 17:231-242. Azim, M.E., M.C.J. Verdegem, A.A. van Dam and M.C.M. Beveridge. 2005. Periphyton: Ecology, Exploitation and Management. CABI Publishing, Wallingford, UK. Bratvold, D. and C.L. Browdy. 2001. Effect of sand sediment and vertical surfaces (Aquamats™) on production, water quality, and microbial ecology in an intensive Litopenaeus vannamei culture system. Aquaculture 195:81-94. Browdy, C.L, J. Hargreaves, H. Tung and Y. Avnimelech. 2014. Proceedings of the Biofloc Technology and Shrimp Disease Workshop. Dec. 9-10, 2013, Ho Chi Minh City, Vietnam. The Aquaculture Engineering Soc. www.aesweb.org/shrimp health.php Boyd, C.E. 1995. Bottom Soils, Sediment, and Pond Aquaculture. Chapman & Hall, New York, NY USA. De Schryver, P., R. Crab, T. Defoirdt, N. Boon and W. Verstraete. 2008. The basics of biofloc technology: The added value for aquaculture. Aquaculture 277:125-137. FAO (Food and Agriculture Organization of the United Nations). 2016. The State of World Fisheries and Aquaculture 2016. Contributing to food security and nutrition for all. Rome. Italy. McIntosh, R. 2000. Changing paradigms in shrimp farming: 5. Establishment of heterotrophic bacterial communities. Global Aquaculture Advocate 3(6):52-54. Milstein, A., Y. Peretz and S. Harpaz. 2009. Culture of organic tilapia to market size in periphyton based ponds with reduced feed inputs. Aquaculture Research 40:55-59 Ray, A.J., G. Seaborn, L. Vinatea, C.L. Browdy and J.W. Leffler. 2012. Effects of biofloc reduction on microbial dynamics in minimalexchange super intensive shrimp (Litopenueos vannemei) culture systems. Journal of the World Aquaculture Society 43:790-801. Reddy, K.R., T.C. Feijtel and W.H. Patrick. 1986. Effect of soil redox conditions on microbial oxidation of organic matter. Pages 117-156 In: Y. Chen and Y. Avnimelech, editors. The Role of Organic Matter in Modern Agriculture, Martinus Nijhoff Pub., Dordrecht, The Netherlands. Scott, S., and R. McNeil. 2011. Aquamats: how to provide habitat, feed, and biofiltration for hatchery and nursery tanks. Hatchery International 2:19-21. Taw, N. 2010. Biofloc technology expanding at white shrimp farms. Global Advocate 10:24-26. The specific system described here offers a clear advantage as an intermediate step to family farmers seeking to adopt more intensive production practices. The system allows for the use of a moderate stocking density, gradual introduction of pond lining and aeration, less vulnerability to failure of the aeration system and gradual adoption of more sophisticated technologies and practices. After gaining experience with fixed biofilm systems for a period, farmers may then choose to evaluate the suspended BFT system.
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