WWW.WAS.ORG • WORLD AQUACULTURE • SEPTEMBER 2016 67 Notes M. Menaga, Division of Aquaculture, ICAR-Central Institute of Fisheries Education, Panch marg, Off-Yari Road, Versova, Andheri(w), Mumbai-400061, India mena.fishcos@gmail.com. TABLE 1. Mean production values from two biofloc nursery raceways with Litopenaeus vannamei conducted at Advanced Research Farm Facility, Madhavaram, Chennai, India. System volume (m3) 40 Stocking density (PL/m3) 6000 Salinity (ppt) 7 Initial weight (g) 0.39±0.01 Final weight (g) 1.90±0.09 Specific Growth Rate 5.59±0.30 Weight gain (g) 1.50±0.10 Feed Conversion Ratio 0.84 Protein Efficiency Ratio 2.79 Survival (%) 91.2 Yield (kg/m3) 0.35 Days 30 Four water top-offs at 10% evaporation rate (m3) 16 Total water consumption (m3) 56 TABLE 2. Investment costs for nursery raceway for rearing Litopenaeus vannamei. ITEM COST (US$) Raceway tanks (two of 50 m3) 1263 Green house 1114 Blowers (10 hp & 5 hp; one each) 1784 Generator (15 KVA) 1486 Rapid sand filter (20,000 LPH) 595 Borewell , water pump and airline 1486 Miscellaneous 223 Total 5870 TABLE 4. Economic feasibility of annual operation of a biofloc nursery system. ITEM Expected annual yield, assuming 95% survival (kg/m3) 8.5 Number of crops per year 5 Estimated annual seed production 228,000 Cost of production (US$/seed) 0.01 Total expected returns @ US$ 0.03/ seed for one crop (US$) 6840 Net returns per crop (US$) 5526 Net returns per year (US$) 27,630 TABLE 3. Variable costs to raise one nursery crop in raceways. ITEM COST (US$) Shrimp seed (6000/m3) 892 Inputs to produce floc 15 Feed (30% protein) 27 Power 45 Fuel for generator 30 Labour 89 Interest on Investment cost (fixed for one crop) 186 Miscellaneous 30 Total 1314
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