58 SEPTEMBER 2014 • WORLD AQUACULTURE • WWW.WAS.ORG stocking in reservoirs, thereby saving transport costs and losses from transport mortality. On average, at least 70 percent survival of fingerlings can be achieved following the procedures outlined. In the case of table-fish culture, 70-80 percent survival is assured (Das et al. 2009). Stocking Healthy carp fry at 12-15 mm or even up to 30 mm are preferred for raising fingerling in cages in Indian reservoirs. Advanced fry above 45 mm should be avoided for growth in cages to fingerlings, inasmuch as in most occasions these fry had fungal diseases like Saprolegniosis if collected from nurseries. A stocking density of 250/m3 of 12-18 mm size carp fry is most suitable for cages installed in reservoirs of India. In case of table-fish, fingerlings with stunted growth and a size of 100-150 mm should be selected for Indian major carps, other carps with lower sized species. The stocking density is maintained at 10/m3 (Das et al. 2008) for India major carps and 50/m3 for air-breathing species and prawns. Bags with fry were kept inside cages for at least one hour for temperature equilibration. Fry were then dipped in 5-6 percent salt solution then a potassium permanganate (5-8 percent) solution for 1-2 minutes and then released to the cage. Raising carp fingerlings in cages generally requires 2-4 months, depending on lake productivity and the quality of supplementary feeds. For production of table-sized fish, 4-6 months are required. If natural productivity supports growth of the stock, the time required is less. Cage culture for raising table-sized fish in Indian reservoirs is more advantageous and economical than growing in pens or nurseries. One battery of 16 cages with a cage size of 4 m × 4 m × 3 m can produce two crops of table fish and one crop of fingerlings from fry per year. Indian major carps, freshwater prawn and airbreathing species can be grown from April to November and fry to fingerlings of exotic carps (common carp and grass carp) can be grown from December to March. Supplemental Feeding Feeding is essential for growing fry to fingerlings in captivity because natural food in many Indian reservoirs may be insufficient for growth even to only fingerlings. In general, rice polish and mustard oil cake in equal parts, with a blend of vitamins, amino acids and minerals at 0.01 percent was applied as supplementary feed for carp fry. In general, the fine flaky powdered form of rice polish/wheat polish/ maize polish and mustard oil cake were mixed together, blended with vitamins-amino acid-mineral mixtures, and spread over the water surface in cages twice daily (0900 h and 1700 h) at 4-5 percent of body weight. Initially 3-4 kg feed a day is applied per cage. In case of table-fish production, floating feeds of high protein content must be selected. Extruded feed with 30-38 percent protein was required for growing table-fish of carps, air-breathing species and prawns. Feeds remained floating on the water surface for a time, then settled slowly, thus progressively favoring the feeding habits of surface feeders, such as catla, first, then the column feeder rohu and finally the bottom feeders mrigal, common carp, air-breathing species and prawns. Cage Maintenance Regular monitoring of some water quality parameters, including dissolved oxygen, pH and free ammonia, inside cages is necessary. Normally in Indian reservoirs, with the objective of raising fingerlings in cage culture, water quality is not conducive to good fish health and on very rare occasions with a dense algal bloom, some parameters cause stress for the fish. Therefore, cages should be cleaned with soft coir brush fortnightly to remove biofouling organisms like algae, sponges and debris. Routine checking for loose twine, torn meshes from predators, anchors and sinkers is also necessary. Fish Stock Monitoring Prophylactic measures should be followed at least fortnightly and when necessary by lifting out fry inside the cages, soaking in salt solution (2-3 percent), followed by permanganate solution (4-5 percent) for two minutes to eradicate ecotoparasites and make the fry and aquatic environment more healthy. Also, a potassium permanganate solution (10-20 percent) may be spread on water surfaces inside cages. At times a lime solution may be spread inside cages to clear water. A bath with malachite green at 0.001 percent was used every 15 days to avoid any fungal attack in stocked crops. Fish health can be checked easily by noticing the feeding habits of fry when feed is applied. Regular sampling for growth assessment facilitates the feeding policy and harvesting schedule. Economics of Production of Fry to Fingerlings in Cages The capital investment for a battery of 8 cages, covering an area of 120 m2 with a working volume of 320 m3, required US$ 65.87/crop and a recurring cost of US$ 292.40/crop. So, production cost per crop including depreciation, interest, additional expenditure, devaluation of money was US$ 448.20. The market price of 70,000 fingerlings is US$ 1200, including transport, for the first two years and US$ 1496 for the next three years. 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