1. Definition
Types of aquaculture in rice fields: combined production of rice and fish or shrimps/prawn; alternating and/or simultaneous crops of rice and fish or shrimps/prawn; use of rice fields as nurseries.
2. General requirements
Adequate irrigation and drainage facilities, absence of seepage; suitable dikes and channels; selection of species for culture that are not harmful to rice.
3. Advantages
Additional protein production, additional income, off-season occupation; higher rice yield; control of pests and weeds, etc.
4. Disadvantages
Requirements of extra quantity of water, extra expenditure for strengthening bunds, meeting requirements of particular types of rice and fish, reduction in rice cultivation area, toxicity of pesticides to fish.
5. Required characteristics of rice for combined culture
Strains tolerant of deep water and low temperature.
6. Criteria for selection of species for culture in rice fields
Ability to thrive in shallow waters; tolerance of high temperature, high turbidity and low oxygen levels; quick growth; compatibility with rice production.
7. Cultivable species
Common carp, Asiatic carps, tilapias, catfishes, milkfish, Trichogaster pectoralis, tench, mullets, cock-up, murrels, buffalofish, bass, pejerrey, prawns, etc.
8. Water and soil conditions
Depth of water required in relation to type of rice and species cultivated; controlled irrigation for maintaining desired depth, possibility of using brackishwater rice fields for culturing euryhaline and other salt-tolerant species; relation of soil fertility and rice farming practices to fish and shrimp/prawn production.
9. Preparation of rice field for culture
Raising and strengthening of bunds; determination of width and height of bunds in relation to depth of water desired; construction of channels, cross channels and rescue pits; and their dimensions; construction of temporary low inner bunds bordering channels; installation of water control (inlet and outlet) devices with screens; spillway for floodwater escape; planting distance between rice plants; fertilization with organic and/or inorganic manures; rates of fertilizer application.
10. Culture operation
Time of stocking fry, fingerlings or yearlings in relation to rice transplantation, and growth; monoculture and polyculture; stocking rates in relation to type of culture; period of culture; species cultured, size of stocking material; fertilization and artificial feeding, manipulation of water level during and after weeding; method of safe application of agricultural fertilizers during culture; permissible doses and methods of application of pesticides; fertilizers used; methods and rates of application; rates of production; measures for protection from predators; method of harvesting.
11. Economics of culture in rice fields
Practicals
Experimental rice field fish culture with selected, locally available species.
