28 DECEMBER 2017 • WORLD AQUACULTURE • WWW.WAS.ORG In the rice-fish system using a refuge with a peripheral trench system, an on-farm trial was conducted in Kyrdem village to assess the growth of common carp in a rice-fish system with an area of 0.17 ha divided into two plots. Fish in one plot were provided with supplementary feed and fish in the other plot were not fed. The field was prepared using a refuge system with a peripheral trench and a central cross-trench. In the rice-fish culture system without a peripheral trench system, an on-farm trial was conducted in four villages of Ri-Bhoi district (Kyrdem, Sohrublei, Mawtneng, Nongthamai) to assess the growth of common carp in a rice-fish culture system with an area of 0.5 ha among five farmers. The rice field had a refuge and a central cross-trench, but no peripheral trench. Rice-Fish Management The plots used for rice-fish culture were planted with the Shashrang rice variety (Fig. 5) and were fertilized with cow dung at 3000 kg/ha per month. Fish were fed with a mixture of rice bran and mustard oil cake at a ratio of 1:1, made twice daily (morning and evening) and applied by broadcasting. Fish were fed at a daily rate of 3 percent of total fish body weight. Common carp fingerlings with an average weight of 2.5-3.0 g and average length of 5 cm at a density of 4000/ha were stocked into rice fields 21 days after transplantation of rice seedlings (Fig. 6). A border fence of nylon mesh was erected to prevent fish escape during heavy rains. A daily water level maintenance check was done and sampling was conducted monthly to monitor fish growth and health status (Fig. 7). No chemical insecticides or pesticides were applied during the rearing period. To harvest fish, water was drained through the outlet pipe, thus allowing fish and water to accumulate in the central channel of the rice field. Fish were then easily caught with a hand net (Fig. 8). Fish were placed in large plastic buckets and held alive. Trial Results In the system with peripheral channels, the total rice harvest was around 3824 kg/ha (650 kg). In the system without the FIGURE 3. Layout of rice-fish culture using refuge /fish pit with peripheral trench and central cross trench system. FIGURE 5. Transplanting rice seedlings into a rice-fish plot. FIGURE 4. Preparation of peripheral trenches in a rice field used for rice-fish culture.
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