Rice fish farming can contribute to household income, contribute to food security and nutrition and contribute to improved sustainability of rice production. Generally two production systems have been recommended for culturing fish in the rice fields. They are, Simultaneous or Concurrent Method and Alternate or Rotational Method.

Selection criteria of rice field

• The field must hold water continuously for several months. The field should be hold water to a depth of 30 cm.
• The plot should be comparatively flat
• The land should be selected keeping in view that it will not be over flooded.
• The soil of the land should hold much water. Clay soil is better for this purpose and the soil pH should be around 6.5-7.5
• Those fields where water remains even after harvest of paddy that is, there should be water, which is sufficient to continue fish culture.
• Fishes can be grown unaffected by chemicals or pesticides used to protect paddy.
• In land with slopes, a high dyke on the uphill side at the field is usually not needed. The layout of the land will help to confine the fish, if the rice field is basin shaped.  This can save a lot of work because middle of the field is deepest portion and a very little effort is required to raise the dykes.
• The paddy field should have strong dykes to prevent leakage and to retain water up to desired level /depth.
• The plot should be at the close vicinity of the farmer’s house so that better care can be taken up.

Selection criteria of fish species

• The fish should be capable of tolerating very shallow water level.
• Should withstand higher temperature (up to 40^OC) and variable temperature fluctuations
• Those species, which can withstand fairly high turbidity of water and poor oxygen concentration.
• The species, which have faster growth rate and should have desirable characteristics to grow to marketable size in short duration at the time of harvesting the rice.

Selection of rice varieties

• The variety of paddy should be high yielding
• The variety should be highly disease resistant and susceptible to less attack from pests.
• Local paddy varieties of medium to long duration with non lodging characteristics are suitable.

Preparation of fields and other considerations

1. Dyke construction :

Embankments should have a height of 40-50 cm. Since water level for rice does not exceed 20cm, such embankments will already have a free board of 20-30cm. This is sufficient to prevent fish from jumping over.

2. Provision of weirs and screens :

Three types of screens can be provided to prevent escape of fish and to prevent entry of predatory fishes to the plot: e.g. bamboo slats, a basket, and a piece of fish net materials even a well perforated piece of sheet metal.

3. Provisions of proper drains :

The common practice is to temporarily breach a portion of embankment for water to get in or out and once the purpose is finished the breach portion be repaired. Bamboo tubes, hollowed out logs, metal pipes or bamboo chutes are also used.

Depending upon the slope of the land three types of layout for construction of rice fish culture plot has been proposed :

• Perimeter trench model,
• Central pond model,
• Lateral trench model.

i. Perimeter trench model :

In this trenches are dug out in the periphery of the paddy field and the paddy cultivation area remains in the middle of the plot in zone of moderate elevation. In a plot of 1 ha, the area in the central part of the field for paddy cultivation is about 0.67 ha. The perimeter trenches may occupy about 0.2 ha and perimeter dykes may occupy another 0.12 ha. Design and construction is that the trench is about 6 meter at the top, 3.5 m at the base and depth is 1.2m. The perimeter may be 1 m in wide at the crest and 3 m at the base.

ii. Central pond model :

In this case fish culture area remains at the center or at the middle of the plot and the paddy growing areas lies surrounding the pond. In a plot of 1 ha area, part of the field for paddy cultivation is about 0.65 ha and the area for the fishpond is 0.35ha with peripheral dyke space of 0.002 ha. The dimensions of perimeter dyke may be 20cm in width, base is of 50 cm width and height is of 30 cm.

iii. Lateral trench model :

Trapezoidal trenches are dug at the sides of paddy plot of dimensions top width 18 m, base 15m and depth is of 1.5 m. There is also to be a peripheral dyke like other two previous cases. In a plot of 1 ha area; part of the field for paddy cultivation is about 0.61 ha and the area for the fishpond is 0.27ha with peripheral dyke space of 0.12 ha.

Water management

Continuous flooding up to the maximum tolerated by rice without affecting its rice production is recommended and it is generally 15-20 cm. At that depth, the effective water depth of 65-70 cm is available to the fish in refuge. This is sufficient to provide the fishes a cooler place when the shallow water over the rice warms up to as high as 40^OC. The increased depth means a greater volume of water for rice –fish culture.

Fertilization

Application of fertilizers increases the nutrient concentration in water, which flourish the growth of phytoplankton, which are directly consumed by the fish or support good growth of zooplankton. Compost fertilizer for deep-water variety @30 tons per ha can be applied. In organic fertilizers for deep water variety Paddy as Nitrogen @120kg/ha, P₂0₅ @ 60 kg/ha and K₂0 @ 60 kg/ha can be applied.

Stocking patters

Rice fish culture may involve the stocking of young fry for the production of fingerlings (nursery operation) or the growing of fingerlings to marketable size (growing operation). Rice fish farming may either be the culture of only one species (monoculture) or a combination of two or more species of fish and crustaceans (polyculture). Generally, stocking density of fish depends on its size, species and the fertility of the land. It is best to wait until the rice is well established before releasing fish seed. Fish can be stocked once two or three tillers have appeared for which the usual waiting is 1- 3 weeks after transplanting or 4-6 weeks after seeding.

Feeding

To boost the growth of fish, rice bran and mustard oil cake in the ratio of 70:30 @2-3% of the body weight of fishes can be provided.