Jyotish Barman & D. J. Rajkhowa
ICAR Nagaland Centre
In India, farm pond has been an integral part of farming system which stores water during rains and the same is used for giving life saving irrigation. Traditionally farm ponds were made either at individual level or on community basis for harvesting rain water or run-off water. However, in many areas the soil type is such that it cannot hold water. In such areas it is essential to seal the pond to reduce seepage and percolation losses. The widely used practice is to lining of ponds with polythene sheet. These polythene lined ponds can store water which can be used as source of irrigation for standing crops at critical growth stage. Apart from irrigation such ponds can be readily used to culture fish. With proper management measures a production upto 2000 – 2500 kg per hectare (1 hectare =7.5 bigha) can be achieved.
Pond Preparation:
• While preparing the pond for plastic lining, an inlet should be provided to allow rain water/surface run-off to enter the pond.
• Similarly provide a suitable outlet to maintain the required depth of water and avoid over flow.
• Once the plastic lining is over, apply at least 10 - 15 cm layer of soil over the pond bottom.
• Allow the pond to fill with rain water.
• Once water is filled upto the desired level, apply lime as per the recommended dose after checking the pH of the water. A pH range of 7-9 is considered suitable for fish growth.
• After seven days of liming apply cow dung @ 200 kg/bigha (1 bigha = 14400 sq ft.)or Poultry manure @ 80 kg/bigha or pig dung @ 100 kg/bigha initially.
• Then apply urea @ 1.5 kg/bigha and SSP @ 2 kg/bigha. Application of fertilizer and manure shall ensure better growth of planktons – the natural food of fish.Slowly the water colour turns green. Appearance of greenish colour indicates that there is sufficient growth of fish food organisms and the pond is ready for stocking fish.
• Unlike conventional fish farming in earthen pond, application of manure and fertilizer in plastic lined pond is less as the soil water interaction is less.
Stocking of fish
• Selection of fish to be stocked depends on the preference of the grower. However, the most commonly cultured fish is the six species composition of carps viz. Catla, Rohu, Mrigal, Common carp, Grass Carp and Silver carp.
• A total of 8000 – 10000 nos. of fingerlings can be stocked in one hectare pond area.
• Since, the rearing periods is limited to 7-8 months, try to stock 10 cm size fish or stunted yearlings to achieve better growth.
• Fish should be stocked in the following ratio; Catla-20%, Rohu 25%, Mrigal-15%, Common carp – 10%, Grass carp - 10% and Silver carp – 20%.
• Fish brought in oxygen packed bag should not be released directly into the pond.
• Keep the plastic bag floating on the water surface for atleast 30 minutes and then open the bag mouth and allow the fish to swim into the pond.
• Stocking of fish should be done during cool hours of the day especially in morning time.
• Never stock fish in noon time as the water temperature is high during noon hours and the stocked fish may die due to temperature shock.
Post-stocking management
• After stocking, the fish has to be fed with supplementary food daily. This is because the production of natural food in plastic lined pond is less and therefore cannot fulfil the total food requirement of the stocked fish.
• Rice polish, rice bran, wheat bran, mustard oil cake (de-oiled), ground nut oil cake are some of the ingredients used as supplementary feed for fish.
• The feed is prepared by mixing any one of rice polish/rice bran/wheat bran with soaked mustard or groundnut oil cake in equal proportion and then by adding mineral mixture powder @ 1% of the total feed prepared.
• The prepared feed can be made into dough and put into the pond.
• Alternatively, commercial fish feed available in the market can also be fed to the fish.
• In areas where integration with pig/cattle/ poultry is possible, the waste material alongwith the dung can be flushed into the pond. This shall serve as manure for plankton growth as well as food for fish. This way the cost incurred on supplementary feed can be minimised.
• For grass carp, banana leaves, leftover leaves of vegetables grown on the embankment can be provided. Apart from these, grasses like para, napier, etc can also be fed to grass carp.
• Sometimes, due to excessive deposit of manure, plankton or algal bloom may appear. In such cases, the bloom should be removed immediately manually. The best way to remove the bloom is by dragging fine meshed net.
• Also, when bloom appears, stop supplementary feeding as well as manuring till bloom disappears.
• In summer months, the plastic line pond water temperature increases. This adversely affects the metabolic activity of the fish. Hence, it is necessary to provide shelter for the reared fish.
• Fish shelter can be provided by growing floating aquatic plants on the pond surface. Care should be taken that the plants does not cover more than one-third of the total water surface area.
• Periodic checking of pH is necessary to ascertain the requirements of lime. If the pH drops below 7, lime has to be applied.
• Liming during winter months is essential even if the pH is within the desired range. This is because fish are susceptible to diseases and lime act as a prophylactic agent.
• A major problem encountered in plastic lined ponds is the tearing of the lining materials. This may happen due to frequent human interference or due to rodent.
• Rodents cut the lining materials resulting in loss of water due to seepage. Therefore, one has to keep a strict vigilant and take appropriate measure to control rodents.
• Similarly, frequent walking over the polythene sheet should be avoided.
• After seven months of rearing or when the water level decreases, the fish should be harvested. Harvesting should be done either by cast net or drag net. Care has to be taken that more person does not enter the pond.
• From one hectare pond area, a production of 2000 - 2500 kg (285-350 kg per bigha) can be obtained in 7-8 months rearing period.
