Giant Freshwater Prawn Farming
Farming of giant freshwater prawn, Macrobrachium rosenbergii is a growing industry in
India. Generally prawn ponds are shallow having
depth of 1.5 to 2.00 meters.
Preparation of Pond:
Pond preparation includes checking and repair of sluice gates and eradication of unwanted species, liming, placing of hide outs, manuring and filling of water. In older ponds, pumping out the water and drying helps in elimination of unwanted species. Drying helps mineralization of bottom soil and improves the productivity of the bottom sole. Disease spreading micro organisms and parasites also can be eliminated by drying. Ploughing of bottom soil after drying helps removal of obnoxious gases. In undrainable ponds, eradication can be done by poisoning. Poisons of plant origin, like mahua oil cake, tea seed cake derris root powder are advisable. After eradication, liming and ploughing can be done. Liming helps in disinfection of pond bottom and improves the fertility of the bottom soil. The quantity of lime could be around 200 kg to 1000 kg based on the pH of the soil. After drying, liming and ploughing, the pond bottom should be kept in a moist condition for a week to facilitate bacterial action. Then manure can be applied. Manuring helps the development of worms like tubifex, zooplankton, algae, etc.
Laying of shelters: Freshwater prawn are cannibalistic. They grow by moulting. Moulting is a process by which the old exoskeleton is shed and new exoskeleton is formed over the body. It takes nearly 24 hours for hardening of the new exoskeleton. During that period moulted prawns require protection from other prawns. Tile, bricks, etc., can be provided in the pond as hide outs. Discarded PVC pipes, earthern pipes can also be used as hide outs. Apart from hide outs, it is advisable to keep some floating weeds like Eichornia, Pistia and duck weed.
Stocking the pond: 7 to 10 days old (PL 7 to 10) post larvae is the ideal age group for transportation and stocking the pond. Before stocking the PLs are to acclimatized to freshwater, preferably with the pond water itself. The density of stocking depends on the intensith of management. For semi-intensive culture with a targeted production of 3 to 3.5 tonnes per year per hectatre, 75000 PLs or 60000 juveniles can be stocked.
During the rearing period, artificial diet is given to the growing prawns. Water quality parameters are to be checked regularly. Disease control measures are to be followed by maintaining a healthy environment, avoiding over stocking, etc. Harvesting should be done by netting the pond, after removing the hide outs. Harvesting should be done during early hours when the temperature is less. After harvesting the prawns are cleaned in freshwater and are iced and transported.