WWW.WAS.ORG • WORLD AQUACULTURE • JUNE 2016 49 to it for firmness. The inner netting needs to be changed three times during the 18-mo culture period. Initially fingerlings are stocked into a mosquito net cage. After two months, fingerlings are transferred to cages with 10-mm mesh. After one year, cage nets are replaced with nets of 35-mm mesh to ensure proper aeration and water exchange in the cage as fish grow. Flotation is accomplished by attaching empty floating cans and PVC pipes to the frame. To protect the cage from the bottom mud, galvanized iron poles are extended 61 cm below the cage. Cages are constructed near the shore. Cage construction requires 3-4 days for the entire family, with help from neighbors. Cages are checked for fouling and tears regularly. Damage to cages or tearing of nets can lead to escape of fish into the wild. Regular cleaning of the cage net is necessary to avoid clogging of mesh. Fish waste that accumulates at the cage bottom and dead fish are removed regularly. Stocking fingerlings. Seabass fingerlings (5.5-cm each) were procured from the RGCA, Tamil Nadu. Each oxygen-filled polythene bag with 100 juveniles was transported during OctoberNovember. Farmers normally form procurement groups to share expenses of transportation and associated costs. Seed bags were normally transported in air-conditioned vans for 1,000 km, incurring an average transportation cost of US$ 671-745 per trip to bring 10,000 juveniles. During transportation 15-20 percent of the fish die due to stress factors and the acclimation process. Farmers stock 5,000-6,000 fingerlings per cage and only 1,000-1,200 survive, related to cannibalism during juvenile stages. Normally farmers culture seabass for 18-20 months to achieve 3-4 kg. Some farmers have experimented with stocking stunted fingerlings procured from private hatcheries in Vijayawada. However due to disease problem the survival rate was very poor and one farmer lost US$ 7,455 on seed and transportation. The quality of seabass fingerlings needs to be maintained to maximize survival during transportation. Over the years, the demand for seabass fingerling production has been increasing and the production of fingerlings has increased from 436,000 fingerlings in 2009 to 1 million fingerlings in 2013-14. The seed of other fish such as mangrove red snapper Lutjanus argentimaculatus and pearl spot Etroplus suratensis are collected from estuaries by hook and line fishing. One fish farmer stocked about 300 Caranx ignobilis in a cage. Stocking density increased from 2000 fingerlings per cage in 2009 to 6000 fingerlings during 2015. The stocking density of red snapper and other capture-based fingerlings was much less compared to seabass and depended on the number caught fishing. Changing salinity increases the risk of mortality with pompano. Feeding. During the first and second month, farmers use shrimp feed at 200 g per 1000 juveniles of 5-6 cm. Feeding is done three times daily. Weaning fingerlings to natural food is carried out within a week. After two months, fish are fed a fish paste of mainly sardine. Each box of 30 kg fish waste cost around US$ 11.93. Fish waste was collected from Byndoor and Uppunda fish market at US$ 0.15/kg. From the third month onwards, small pieces of sardines are procured from fish markets and agents for US$ 0.30-0.89 /kg. Normally one laborer is required for feeding and cage maintenance. From the fourth month onwards, 6-10 kg of trash fish is fed daily. Farmers have tried floating feed purchased from feed companies. However, during high tide, floating feed escapes from the cage into estuaries. Based on information collected from farmers, approximately 7-8 kg of trash fish is required to produce 1 kg of seabass. The FCR for seabass fed trash fish is very high, ranging from 4.1 to 8.1(FAO 2006). For wild captured seeds of snapper and trevally, fish waste chopped into small pieces was fed. Although punctual feeding is required, excess feeding of trash fish pollutes water. The demand for feed per cage ranges from 200 kg per month to 2700 kg per month when fish approach harvest size at 18-20 months. The opportunity cost of trash fish is the price paid by the fishmeal/ fish fertilizer industry, dry fish producers and other crab and fish farmers. Thus, many feed manufacturers assert that there is potential to reduce FCR by shifting to manufactured feed with 25 percent protein. They claim that feeding trash fish with commercial feed will result in good growth with reduced production costs and shorter culture periods. Feed cost is expected to increase four times with the use of commercial feed throughout culture at the current market price of trash fish or wild-caught fish. With manufactured feed, growth would improve and the culture period could be substantially reduced. Growth was optimum up to 1 kg after one year and farmers could minimize the risks of disease and feeding cost by harvesting fish at that size. Further, with commercial feed, direct dependence on trash fish could be reduced, promoting conservation and alternative uses of wild fish. Harvesting and Marketing. Harvesting begins after18 months, normally during June-July, when fish reach 2-3 kg. Cages are taken to shore and hauled from the water. Harvesting requires around 20 labor-days for lifting cages, dragging to the shore for 2-3 hours and loading fish into a truck. The average harvest rate was 800-900 fish with a stocking density of 6,000 fish, but survival was as low as 20 percent. Farmers observed disease in fish during the 12-18 month culture period. The occurrence of harmful algal blooms was frequent in the estuary and farmers were at high risk when water quality deteriorated. Marketing agents from Goa and Karwar came to the site and bought seabass at US$ 5.22-5.96/ kg. Cage farmers sell fish during the monsoon so that they can fetch a good price. Marketing channels directly linking producer and consumer can ensure better returns to the cage farmer. Factors Contributing to Success The success of technology depends on the interest of the innovating farmer, who invests time, effort and capital. Small-scale cage culture was undertaken by a few innovative farmers after observing the failure of the open-sea cage culture demonstration experiments in Uppunda by CMFRI. Traditional fishers were interested in developing a cost-effective and cheaper technology, which would need less time to construct and transport cages to water bodies, so they thought of installing cages in estuaries. They gathered leftover materials from the open-sea cage culture demonstration and constructed their own rectangular cage. The objective was to minimize the environmental risks and develop small-scale cages, which could be constructed and installed with their own resources and capital. They modified (CONTINUED ON PAGE 50)
RkJQdWJsaXNoZXIy MjExNDY=