56 SEPTEMBER 2014 • WORLD AQUACULTURE • WWW.WAS.ORG Presently the annual fish yield from small, medium and large reservoirs is 100, 75 and 50 kg/ha, suggesting substantial scope to enhance fish yield through wild capture and culturebased fisheries in these water bodies. The success of auto-stocking is very low in Indian reservoirs, especially smaller ones, often a result of recruitment failure. Therefore, regular and sustained stocking is needed to augment fisheries in reservoirs. Stocking with the appropriate species, size (>100 mm) and at the right time is essential to optimize fish yield from reservoirs. Production of fingerlings in cages offers the opportunity to produce fingerlings that can be used in stock enhancement programs for Indian reservoirs. Apart from raising fingerlings for reservoir stocking, cages can also be used to support production of high-value tablefish and crustaceans. Evolution of Freshwater Cage Culture in India In India, cage culture was attempted for the first time in 1970 in three environments: 1) swamps marked by low dissolved oxygen concentration, using air-breathing fishes, 2) running waters of the Yamuna and Ganga Rivers at Allahabad, using major carps and 3) and a static water body in Karnataka, using common carp, catla, silver carp, rohu, snakeheads and tilapia. The Central Inland Fisheries Research Institute (CIFRI) attempted cage culture in the 1970s with the production of air-breathing fish in cages but got poor results. A few preliminary trials on cage aquaculture were attempted and recently CIFE, Mumbai did some isolated work on cage culture for raising fingerlings as well as table-fish in reservoirs such as Powai (Maharashtra), Govindsagar (H.P.), Halali (M.P.), Tandula (Chattishgarh) and Dimbe (Maharashtra). Later, a number of attempts were made to produce cage-stocked fish, especially fry to fingerlings (Banerjee et al. 1979). Culture of silver carp and common carps was tried in floating cages in Sankey Tank, Bangalore, but success was unremarkable. With the lessons learned, cages were subsequently used for raising catla fingerlings in Karnataka (Govind et al. 1988), also with little success. Production of fingerlings for stocking reservoirs was tried in Govindsagar (H.P), Getalsud (Ranchi), Gularia (U.P.) reservoirs, with poor success because proper monitoring was not initiated. Cage aquaculture was initiated in CIFA at Hessaraghata farm, Bangalore with one unit established in 1997-1998 and later at Kaushalyaganga farm, Odisha in a pond system with major improvements in cage design. While the objectives of cage aquaculture were not properly understood, these experiments served as good demonstrations. More recently cage aquaculture experiments were conducted in Walvan Reservoir (Maharashtra), with fry to fingerling culture of Tor putitora and T. khudree (Kohli et al. 2002). During 20052006, floating cage culture experiments were conducted in Kabini reservoir, Karnataka for raising fingerlings for stocking, with moderate success, defined by a survival rate of around 40 Cage Farming in an Indian Reservoir A. K. Das, D. K. Meena and A. P. Sharma percent. Some trials on cage aquaculture were conducted during 1998 onward for production of fingerlings but results were not optimal. CIFRI has banked on the success of producing fingerlings for stocking reservoirs in floating cages installed in different agroclimatic zones of India (Madhya Pradesh, Uttar Pradesh, Bihar, Jharkhand and Northeast states). Cage Design and Fabrication Cage frames can be made with locally available bamboo, although wood, iron, steel or PVC frames can be used, but these are costly. Bamboo is the cheapest material available to construct frames and it will last for at least three years with 5-10 percent annual replacement, as necessary. Two frames are required, one above the other to hold floats in place. In the case of producing table-fish, only one frame is required. A full grown ripened bamboo, at least 10 m in length and 8-9 cm in diameter at the base, is suitable for cage frames. To make a battery holding 16 cages, each 16 m2, the battery should be 18 m long and 18 m wide. To make such a frame, 60 bamboo lengths are required for the top frame and 60 for the lower frame. Drums are placed between the two frames of bamboos, mostly in the corners and near joints to provide the frame with balanced flotation. Steel drums are attached to galvanized iron (GI) and bamboo frames with iron brackets. They are tightened to the frame with two types of GI wire, thicker wire (4 mm) at the central portion and thinner wire (2 mm) for encircling the drum with the frame at the end sections to accommodate turbulent wave action, especially during summer and monsoons. Drums are coated with acrylic paint prior to setting between frames. About 16 cm of the 58-cm diameter drum remains under water when the assembly is complete. Catwalks can be made locally with bamboo crisscrossed with wooden bars or with plywood to provide ease and comfort to cage workers. Catwalks were bolted to a GI frame, with a bamboo frame at the top that was tightened with GI wire. Once the frame is anchored at the cage culture site, net cages (4 m × 4 m × 3 m) were attached to the frame, thus forming a battery of 16 cages. On top, silk ropes are used to tie nets to the bamboo frame firmly to reduce sagging. The lower bottom corners and the sides of the net cages were tied with sinkers for taut vertical hanging. Hanging net-cages should remain at least 1-2 m above the lake bottom to avoid damage by crabs or other aquatic organisms. Fishers were cautioned not to tie gillnets to the frame, which can lead to damage of net cages. After installation, net cages must be kept under water for at least one week to allow growth of algae on the cage mesh, which would be helpful in reducing injury to stocked fish fry. Species Selection for Cage Culture Species selection depends on local interest and market value. For fingerling production, the species selected were primarily
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