WWW.WAS.ORG • WORLD AQUACULTURE • SEPTEMBER 2014 59 culture period is US$ 986.27. The benefit-to cost ratio is 2.20 and production cost per fingerling was estimated at US$ 0.0064. If the culture period of fingerling is reduced to two months, the production cost would be reduced further to US$ 0.0059/ fingerling. Depreciation The life span of HDPE plastic nets was at least one year and with minor repair, it may be used for two years, depending on the level of management after harvesting. Net cages used for production of fingerlings for two years might be sold at 7-8 percent of their initial procurement price. Hapa nets of ‘Garware’ make (mesh size 10-20 mm, multifilament, knotless) can be used for more than 5-6 years. The lifespan of metal drums used as floats was at least 5-7 years and of this period, 10-12 crops of table-fish and 5-6 crops of fingerlings can be harvested. After seven years of use, drums can be sold at 40-50 percent of their procurement price. Only 27 percent of the surface area of each drum remained under water when used as floats and immediately after the harvest the inundated portion was painted after rotating the drum to expose the previously inundated surface. After one year, the whole drum must be repainted properly to extend its lifespan. Bamboo used for framing normally lasts for two years, requiring a change of 10 percent every year. The bamboo used in underwater frames lasts for more than three years with proper care. After use in cage frames, bamboo might be sold at a price of 5 percent of the initial procurement. If a GI frame is used and maintained properly, a lifespan of more than 15 years can be expected. If a HDPE frame is used, the lifespan can exceed 10 years, provided proper maintenance, such as rotating the exposed portion during the next crop, putting the top portion under water. The thick nylon ropes used to anchor the cage battery can serve for more than 5 years, especially when they remain under water. The silk ropes for tying net cages to the bamboo frame lasts for at least two years. Conclusion and Prospects Despite the unsuitability of wetlands for cage culture, recent studies conducted by CIFRI indicate that raising fingerlings from cages is profitable and, if practiced in Indian reservoirs, could solve the problem of providing fingerlings for stocking those reservoirs. Furthermore, with prolonged, sustained and continued effort, assimilating the lessons learned, CIFRI achieved success in producing fingerlings in floating cages installed in Pahuj Reservoir (U.P.) and Dahod Reservoir (M.P.) during 2007-2009 (Bene et al. 2009). In 2011, CIFRI ventured into raising table-fish of economically important species through cage culture by installing cage facilities with durable galvanized iron frames in Maithon Reservoir (Jharkhand) in 2011. Many modifications and combinations were in practice to increase the cage viability, such as: • Use of different netting material for long-lasting durability without impacting fish growth, • Reduction of the cost of cage installation by replacement of simple pipe with galvanized iron pipe, • Replacement of plastic pipe with painted iron pipe to withstand strong wind action, making it long lasting and for antifouling, and • Provision of flexibility to better maneuver cages. One of the prime objectives of cage culture discussed here is to recommend the rearing of fingerlings >100 mm in length, especially carps, for stocking reservoirs. Nevertheless, a general thinking has arisen among planners to depend more on open waters and culture-based capture fisheries to achieve high fish production through ecosystem management. Against this backdrop, the wide applicability of modified technologies, such as cage culture to enhance fish production, should be adopted. However, more comprehensive investigation is needed to characterize its impact on ecosystems and the sustainable accumulation of capacity for auto-stocking of indigenous fishes in inland open-water systems in general and reservoirs in particular. Notes A. K. Das, Reservoir and Wetland Fisheries Division,Central Inland Fisheries Research Institute, Barrackpore, Kolkata, 700120 Email: archandas@yahoo.com D. K. Meena, Reservoir and Wetland Fisheries Division, Central Inland Fisheries Research Institute, Barrackpore, Kolkata, 700120 Corresponding author email: dkmeenafnb@gmail.com A.P. Sharma, Central Inland Fisheries Research Institute, Barrackpore, Kolkata, 700120 Email: apsharma1@gmail.com References Banerjee, B.K. and B.V. 1979. Experiments on fry rearing in floating nurseries (floating cages) in Getalsud reservoir, Ranchi (Bihar). Pages 1-6 In A.V. Natarajan, editor. Proceedings of the Summer Institute on Capture and Culture Fisheries of the Manmade Lakes in India, CIFRI, 7 July-6 August. Bene, C., E.K. Abban, S.H. Abdel-Rahman., S. Ayyappan, R. Brummett, H.R. Dankwa, A.K. Das, O.A. Habib, P.K. Katiha, J. Kolding, N. Obirih-Opareh, J.K. Ofori, M. Shehata, N.P. Shrivastava and K.K. Vass. 2009. Improved fisheries productivity and management in tropical reservoirs. CGIAR Challenge Program on Water and Food Project Report series, CPWF, 34. Das, A.K., N.P. Shrivastava, K.K. Vass and B.L. Pandey. 2008. Management strategies for enhancing fish production in Madhya Pradesh reservoirs. The 12th World Lake Conference, 1295-1300. Das, A.K., K.K. Vass, N.P. Shrivastava and P.K. Katiha. 2009. Cage culture in reservoirs in India, a handbook. Page 24 In The WorldFish Center, Penang, Malaysia, 1948. Govind, B.V., S. Ayyappan, S.L. Raghavan and M.F. Rahman. 1988. Culture of catla (Catla catla) in floating net cages. Mysore Journal of Agricultural Science 22:517-522. Kohli, M.P.S., S. Ayyapan, S.N. Ogle, R.K. Langer, C. Prakash, K, Dube, A.K. Reddy, M.B. Patel and N. Saharan.2002. Observations on the performance of Tor khudree in floating cages in open waters. Applied Fisheries and Aquaculture 2(1):51-57.
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