58 December 2011 Paddy cum fish culture in north-eastern states of India: A better scope in the exploitation of resources Asem Sanjit Singh1, Manoharmayum Shaya Devi1, Sagar C. Mandal1 and Debtanu Barman*2 The people of North-East India depend on diverse agricultural practices ranging from a variety of shifting aquaculture systems, fallow systems, home gardens and sedentary systems, such as wet-rice cultivation (Ramakrishna 1984, 1992). The system of raising fish from the rice fields probably started in the northeast with the beginning of the rice cultivation itself, because the water logged rice fields form natural habitat for wild fish. It is believed to have appeared first only as the simple capture device (Das 2002). Cultivating rice and fish together has existed for about 2,000 years in some parts of Southeast Asia. However, this beneficial cultivation system was gradually abandoned because of population pressures, decreasing stocks of wild fish and the green revolution, which emphasized high-input monoculture using high-yield rice varieties, pesticides and herbicides. Paddy cum fish culture (PFC) is fish farming with paddy. This system is profitable and sustainable, as paddy and fish can be harvested as a unit from the cultivable area. The wet terrace rice fields where surface and ground water is sufficiently available, can be utilized for development of PFC. However, the plot must be renovated by excavating canals, pools, and trenches to retain water for sheltering the fishes during the summer months. The water stored may also be used for irrigating the plot. The adoption of PFC with open avenues for self-employment, supplement the income of the agriculture farmers and enhance fish production in the state. Rice-fish farming systems have received a great deal of attention in the recent past because of government focus on sustainable rural development, food security and poverty alleviation. Several reviews on historical, socio-economic, and ecological aspects of rice-fish farming have been published in the past decade with either a global or a national focus (Li 1988, Halwart 1994, Choudhury 1995, Little et al. 1996). De la Cruz et al. (1992) provided country overviews for Bangladesh, China, India, Indonesia, Korea, Malaysia, Philippines, Thailand and Vietnam. Fernando (1993) compiled an extensive bibliography on diverse aspects of fish culture in rice fields. Site Selection Integration of fish farming with rice cultivation is crucially dependant on availability of sufficient water for survival and growth of fish without any detrimental effect on rice crops. Therefore, it is, imperative that the plot be renovated for holding sufficient water. Terrace paddy fields and low-lying fields with good sources of water and spacious benches/plots can be brought under this system. At least 60 to 70 percent of the land is made available for paddy cultivation and the rest is utilized for digging small shelter ponds and embankments. Strong and stable dykes are constructed around the plot creating a confinement for fish and to retain more water. The trenches are excavated in the trapezoid form keeping 6 m on top width, 3.6 m at the base and a depth of about 1 to 1.2 m. Characters of Fish Species right for PFC The candidate fish species for the PFC farming system should have the following characteristics: • Thrive in shallow water, • Tolerate temperature fluctuations, • Withstand high turbidity, • Grow to marketable size in a short period. Common Species Culture A wide variety of fish species have been cultured including common carp (Cyprinus carpio), Indian Major Carp including, rohu (Labeo rohita), mrigal (Cirrhinus mrigala) and catla (Catla catla), Chinese carp such as, silver carp (Hypophthalmichthys molitrix) and occasionally grass carp (Ctenopharyngodon idella), tilapia (Oreochromis niloticus) and silver barb (Puntius javanicus) (Gupta et al. 1998). Depending upon the availability and suitability for culture under local conditions, fingerlings of L. rohita, C. catla, C. mrigala, H. molitrix, C. carpio, L. gonius, L. calbasu, L. bata and Puntius spp. were stocked mainly by the farmers in the paddy field. However, tilapia (O. mossam-
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