Fish farming with agriculture

Agri-based systems include rice-fish integration, horticulture-fish system, mushroom-fish system, seri-fish system. In this system, fish culture is integrated with agricultural crops such as rice, banana and coconut, thereby producing fish and agricultural crops under one interlinked system. Rice-fish culture In India, though six million hectares are under rice cultivation, only 0.03 per cent of this is now used for rice-fish culture. This type of fish culture has several advantages such as (a) economical utilisation of land, (b) little extra labour, (c) savings on labour cost towards weeding and supplemental feeding, (d) enhanced rice yield, and (e) additional income and diversified harvest such as fish and rice from water, and onion, bean, and sweet potato through cultivation on bunds. Considering these, it is imperative to expand fish culture in the rice fields of our country. The paddy fields retain water for 3-8 months in a year. The culture of fish in paddy fields, which remain flooded even after paddy harvest, serves an off-season occupation and additional income to the farmer. This system needs modification of rice fields, digging peripheral trenches, construction of dykes, pond refuge, sowing improved varieties of rice, manuring, stocking of fish at 10,000/ha and finally feeding of stocked fish with rice-bran and oilcakes at 2-3% of body weight.

Paddy-Poultry-Fish Integrated Farming

For the culture of fish in combination with rice, varieties such as Panidhan, Tulsi, CR260 77, ADT 6, ADT 7, Rajarajan and Pattambi 15 and 16 are suitable. These varieties not only possess strong root systems but also are also capable of withstanding flooded conditions. Further, they have a life span of 180 days and fish culture is possible for about four to five months after their transplantation. Harvesting is done when fish attain marketable size. Fish culture in rice fields may be attempted in two ways, viz. simultaneous culture and rotation culture. In the former, rice and fish are cultivated together and in the latter; fish and rice are cultivated alternately. Simultaneous Culture For simultaneous culture, rice fields of 0.1 ha area may be economical. Normally four rice plots of 250 m2 (25 x 10 m) each may be formed in such an area. In each plot, a ditch of 0.75 m width and 0.5 m depth is dug. The dikes enclosing the rice plots may be 0.3 m high and 0.3 m wide and are strengthened by embedding straw. The ditches have connections with the main supply or drain canal, on either side of which, the rice plots are located, through inlet-outlet structures of the dikes. The depth and width of the supply or drain canal may be slightly smaller than that of the ditches. Suitable bamboo pipes and screens are placed in the inlet and outlet structures to avoid the entry of predatory fish and the escape of fish under culture. The ditches serve not only as a refuge when the fish are not foraging among rice plants, but also serve as capture channels in which the fish collect when water level goes down. The water depth of the rice plot may vary from 5 to 25 cm depending on the type of rice and size and species of fish to be cultured. The fish species which could be cultured in rice fields must be capable of tolerating shallow water (15 cm), high temperatures (up to 35ºC), low dissolved oxygen and high turbidity. Species such as Catla catla, Labeo rohita, Cirrhina mrigala, Cyprinus carpio, Chanos chanos, Oreochromis mossambicus, Anabas testudineus, Mugil spp., Clarias batrachus, C. macrocephalus, Lates calcarifer, Channa striatus and C. marulius have been widely cultured in rice fields.

Simultaneous Culture Of Fresh-Water Prawn And Rice

Semi-intensive culture of Macrobrachium rosenbergii could be undertaken in rice fields. Unlike for fish-rice culture, bunds for fish-prawn culture are raised so as to enclose 12 cm of water for four months, the period of rice culture. Further, inlets and outlets should be provided with extended screen, say, 0.3 m above water surface to prevent climbing and escape of prawns. One or two small sump pits (1 x 2 x 0.5 m) should also be constructed near the outlet for trapping prawns when water is drained at the time of harvesting. The stocking of juvenile prawns (2-3 cm size) at the rate of 1,000/ha may be done after the rice seedlings are well rooted. No supplementary feeding of prawns is required in this system.

The simultaneous culture has the following advantages:

• Fish increases rice yield by 5 to 15 per cent, which is chiefly due to the indirect organic fertilisation through the fish excrement and also the control of unwanted filamentous algae which may otherwise compete for the nutrients.
• Tilapia and common carp control the unwanted aquatic weeds which may otherwise reduce the rice yield up to 50 per cent.
• Insect pests of rice like stem borers are controlled by fish feeding on them like murrels and catfish.
• Fish feed on the aquatic intermediate hosts such as malaria causing mosquito larvae, thereby controlling water-borne diseases of human beings.
• Rice fields may also serve as fish nurseries to grow fry into fingerlings. The fingerlings, if and when produced in large quantities may either be sold or stocked in production ponds for obtaining better fish yield under composite fish culture.

Limitations in simultaneous culture: The simultaneous fish-rice culture may have some limitations, like (a) use of agrochemicals is often not feasible, (b) maintaining high water level may not be always possible, considering the size and growth of fish, (c) fish like grass carp may feed on rice seedlings, and (d) fish like common carp and tilapia may uproot the rice seedlings. However, these constraints may be overcome through judicious management.

Culture procedure

Five days after transplanatation of rice, fish fry (1 cm) are stocked at the rate of 5,000/ha or fingerlings (8-10 cm) at the rate of 2,000/ha. The stocking density can, however, be doubled if supplemental feed is given daily, particularly if plankton is found depleted after 10 days of stocking fish. The plankton production in rice fields could, however, be increased if some amount of fertiliser more than what is required for rice fields is added. To control the menace of insects, the insecticide Furadon (Carbofuran) may be used at the rate of 1 kg/ha. The insecticide is mixed with basal fertilisers and applied once during the final harrowing. It may be stated that fish grown in insecticide-applied rice fields are safe for human consumption.

After a period of 10 weeks (if stocked with fry) or six weeks (if stocked with fingerlings), the rice fields are slowly drained off and the fish are harvested. The harvesting of fish may be done about a week before the harvest of rice. The growth rate of fish is also moderate in rice fields as the production of plankton, the fish food organisms, is rich. Individual growth of 60 g and a per hectare yield of 500 kg have been reported under the simultaneous culture practice.

Through this practice, fish and rice are cultivated alternately. The rice field is converted into a temporary fishpond after the harvest. This practice is favoured over the simultaneous culture practice as it permits the use of insecticides and herbicides for rice production. Further, a greater water depth (up to 60 cm) could be maintained throughout the fish culture period.

One or two weeks after rice harvest, the field is prepared for fish culture. C. carpio is found suitable for this practice. The stocking densities of fry (2-3 cm) or fingerlings (5-8 cm) for this pracitce could be 20,000/ha and 6,000/ha, respectively. The fry are harvested after 10 weeks, while the fingerlings after six weeks. The average growth of the individual fish under this system has been reported to be about 100 g and a fish yield of about 2,000 kg/ha is possible. Further, it has also been reported that fish yield could exceed the income from rice in the rotational culture.

Coastal saline soil extends from the main sea coast to a few or even 50 km at places interior to the main land. The ground water table under these soils is generally present at a shallow depth and contains high amount of soluble salts. These salts accumulate on the surface of the soil due to capillary rise of saline groundwater during dry periods of the year rendering the soil highly saline. Almost the entire area of the rain fed coastal saline soil is mono cropped in nature. The major agricultural crop of kharif is rice, grown during monsoon period when soil salinity is low. During the rest of the year, the land usually remains fallow due to high salt content of the soil.

The kharif paddy varieties widely used in such areas are Mahsuri, Sadamota, Kalomota, Talmugur, Damodar, Dasal, Getu, Nona-patnai, Jaya, Ratna, Pankaj, Patnai-23, Luni, Cuttackdhandi, Pokkali, Vytilla, Bilikagga, CSR-4, CSR-6, Matla, Hamilton, Palman 579, BKN, RP-6, FR-46B, Arya, etc. Paddy cum brackish water fish/ shrimp culture aims at utilizing the summer fallow period of the coastal saline soil through a short-term brackish water aquaculture without affecting the subsequent kharif paddy crop. This type of activity provides the farmers with a substantial subsidiary income during the fallow season.

In West Bengal, where the salinity is either low or lowered by fresh water discharge diluting the tidal water, the cultivation of fish is undertaken in paddy fields. In pokkali fields of Kerala, summer fallow months are utilized for brackish water aquaculture. The production of fish in such culture varies from 300 to 1000 kg/ha. The brackish water shrimp culture is introduced in a big way in such areas as the remuneration is very high. The species commonly cultured are Penaeus monodon, Penaeus indicus, Metapenaeus dobsonii and Metapenaeus monoceros.

Technical Parameters

The coastal area is mostly low lying, the elevation varying usually between sea level and 8 m above the MSL. Fields having elevation between low and high tide levels are desirable for water exchange during brackish water aquaculture and also for frequent draining of monsoon water during desalination process. The sluice in the embankment is essential for regulating the flow of tidal and drainage waters. The area having more than 1 m tidal amplitude is considered suitable for paddy cum shrimp culture.

Soil quality

Medium textured soils like silty clay or silty clay loam are most suitable for paddy cum fish/ shrimp culture.

Water quality

Heavy monsoon precipitation for the site is essential for desalination of the soil after brackish water aquaculture. Intake of brackish water must be suspended before the onset of monsoon. The cultured species is harvested and then the land is exposed to monsoon precipitation for the purpose of desalination.

Pond construction

The paddy plots should be renovated suitably for the purpose of paddy cum brackish water aquaculture. Construction of an earthen dyke surrounding the paddy plot is essential for retaining water and also for holding the fish and shrimp during aquaculture. The height of the dyke is required to be maintained between 50 and 100 cm depending upon the topography of the plot and tidal amplitude at the site. A perimeter canal is necessary on the inner periphery of the plot. For a one ha paddy plot, the width and depth of the canal may be about 2 m and 1 m respectively. The earth removed from excavating the canal may be utilized for constructing or strengthening the dyke. In addition to the perimeter canal, two cross trenches of about 1 m width should also be constructed at both the directions. The bottom of the trenches should be above the perimeter canal so that during the course of desalination, entire water can be easily removed to the canal. The area covered by the perimeter canal and the trenches will be about 12% of the total land area.

Water supply and drainage

The entry of tidal water during the culture is made through feeder canal and the flow of water into the field is regulated by a sluice gate fitted with wooden shutters and placed at about 30 cm height from the main plot. During high tide, water is taken into the plot after sieving through velon nets and split bamboo mats to prevent entry of any kind of fish/ shrimp and other undesirable species, especially carnivores. Another sluice is used for draining out water from the culture plot to the feeder canal at low tide periods for water exchange, desalination and drainage of excess water. On the entry and exit mouths of the slice gate, wooden shutters are provided to regulate the movement of water.

Pond management

The plots are prepared in two phases, once for brackish water aquaculture and again for paddy cultivation. For aquaculture crop, the plot is sun dried after the kharif harvest. If necessary, to rectify acidic soils, lime is applied depending on requirement of the soil. Usually no inorganic fertilization is done. However, urea may be used in extreme cases of nitrogen deficiency of soils @ 60 kg N/ha. Some shade zones are provided over the perimeter canal with twigs, hay, palm leaves etc., so that during summer the shrimp can take shelter and also hide themselves from predation.

Stocking

The paddy field is made ready for stocking and Penaeus monodon or Penaeus indicus are stocked @ 3 nos/sq.m.

Feeding

Although natural food items have good conversion values but they are difficult to procure in large quantities and maintain a continuous supply. Hence only supplementary feed is given

Harvesting

Complete harvesting is done by draining the pond water through a bag net and hand picking. The average culture period in paddy fields is around 100-120 days during which time the shrimps will grow to 35 gm size. Harvested shrimps can be kept between layers of crushed ice before transporting the consignment to market.

In Kerala, fish and prawn are cultured on rotational basis in Pokkali rice fields. These fields under the influence of Vembanad backwaters, which are in, turn controlled by tides. As these fields are flooded during southwest monsoon (June-Septemeber) rice is cultivated. Fish and prawns are cultured during other periods. Immediately after the harvest of rice, the fields are leased out for the culture of fish and prawns. The young of fish and prawns enter the fields from nearshore waters along with high tides. Suitable management cultures these young until harvest in May. These fields are rich in plankton owing to the decaying of paddy stumps. A prawn yield of 500-1,200 kg/ha has been obtained from Pokkali fields. After the prawn harvest, the water is drained off. Subsequently, the saline nature of rice fields is nullified because of the monsoon rains and the fields are again made fit for rice culture.

Source:

http://www.vuatkerala.ofile:///E:/Animal%20Husbandry/TNAU-Agri%20Tech%20Portal/ani_chik_grower&layer%20mgt.html

http://www.vuatkerala.org/static/eng/advisory/fisheries/culture_fisheries/integrated_farming/introduction.htm