Success Stories In Asian Aquaculture - Library - Network of ...

24 M. Weiminagriculture sector. Meanwhile, the contribution of rice-fish culture to inland aquacultureincreased from 3.5% in 1990 to over 6% in 2007.2.6 Important Systems and PracticesAlong with the development processes, diversified systems and practices of rice–fish culture have been developed and adopted under different environmental conditionsor for different species of aquatic animals across China.2.6.1 Concurrent Rice-fish Farming SystemsCulture of fish concurrently with rice during more or less the same productionperiod is a most typical rice–fish symbiotic farming system. Therefore, the potentialecological and economic benefits of rice–fish integration are assured.Accordingly, specialized earthworks to modify the rice fields to meet the requirementsof both rice and fish are needed. It also requires more careful managementin fertilization, pest/disease control, and water management. The suitable speciesfor culture are those which do not require a long period to reach marketable size ingrow-out culture. Concurrent rice–fish farming is very suitable for rice-crustaceanculture practices.Concurrent rice–fish farming requires good engineering earthwork of the ricefield. Major earthworks for preparation of rice field include reinforcement of fieldridge. The rice field ridge should be at least 10–20 cm higher than the maximumwater level in the rice field. The rice field must be seepage free.Peripheral and central crossing trenches are constructed in the rice field. Theperipheral trench is usually 80–100 cm inside the rice field ridge to avoid escape ofcultured animals. The trench is normally 50–100 cm wide and 60–80 cm deep. Acentral fish pit (5–6 m 2 and 1 m deep) connected to the trench is sometimes dug inthe central area of the rice field in large rice plots (Fig. 2.3 ). The total area of fishtrench and pit usually accounts for 10–15% of the rice field area in order to maintainmore or less the same unit production of rice. In concurrent rice–fish culturesystem, the yield of fish usually ranges 300–900 kg/ha, and that of prawn and crabis in the range of 300–750 kg/ha. Production of crawfish is much higher.The most important management aspects in concurrent systems include watermanagement and use of pesticides and fertilizer. While meeting the requirement ofrice at different stages, minimum water depth should be maintained for culture ofanimals in trenches and pits, 30–50 cm depending on species and weather conditions.Pesticides should not be used just before rain. It is important to avoid the pesticidesgetting into the water when spraying. Organic fertilizer is preferred if fertilization isneeded. Use of ammonium fertilizers should be avoided as it often leads to highammonia level in water, which is toxic to cultured animals.