Fry are raised to fingerling size in rearing ponds in about 3 months period. The package of practices, as developed at CIFRI, for ensuring healthy growth and better survival of fingerlings is as follows.
Rearing ponds may be 0.05 ha to 0.1 ha in area, rectangular in shape with water depth ranging from 1.5 to 2.0 m Seasonal ponds/impoundments are often preferable to perennial ones. Care should be taken to prevent entry of ducks in the rearing ponds too.
The weeds from the shallow small ponds may be economically and easily eradicated by manual labour during summer months.
Removal of unwanted fishes
The methods for eradication of predatory and weed fishes from rearing nponds are same as given in Section 3.3
Liming the pond @ 250-300 kgfha in 3 equal monthly instalments is recommended. The first dose need be applied one week earlier to stocking.
Provision of adequate natural food can be ensured to some extent in the pond through manuring and fertilization at fortnightly intervals. Organic manure (Cattledung) @ 2500 kgfha is applied in 4 equal instalments. While the initial dose is applied about a fortnight before the stocking, the subsequent ones are used on monthly intervals. However, when the ponds are earlier treated with mahua oilcake the first instalment of cowdung can be dispensed with.
Inorganic ferlitizers like urea @100 kgfha or ammonium suplhate @200 kgf ha and single super phosphate @ 100kgfha or triple superphosphate @ 35 kgfha may be applied in 3 equal instalments during the rearing period. The first instalment of inorganic fertilizers is given on second day of stocking and thereafter at monthly intervals, alternating with organic manures. Manuring and fertilization need be suspended if algal blooms or any other adverse conditions appear in the pond
|Catla +Rohu +Mrigal||2:4:4|
|Silver carp + Grass carp||I : 1|
|Silver carp + Grass Carp + Common carp||4: 3: 3|
|Silver carp + Grass carp + Common carp||5 : 1.25 : 3.75|
|Catla + Rohu + Mrigal + Common carp||3 : 4: 1 : 2|
|Catla + Rohu + Mrigal + Grass carp||4 : 3 : 1.5 : 1.5|
|Catla + Rohu + Mrigal + Grass carp||3 : 3 : 3 : 1|
|Silver carp + Grass carp + Common carp + Rohu||3 : 1.5 : 2.5 : 3|
|Silver carp + Grass carp + Common carp + Rohu||4:2:2:2|
Plankton production in the pond can not be maintained at adequate level even after regular manuring and fertilization in view of the heavy stocking density maintained under modern practices. In order to meet the increasing demand, supplementary feed consisting of a mixture of groundnutfmustard oi1cake and rice bran at 1 : 1 ratio by weight in powder form is broadcast every day in the pond during morning hours commencing from the first day of stocking. A generalised feeding schedule may be be as below :
1st month 6~kg
2nd. month 10 kg.
3rd. month 15 kg
Feeding need be suspended if algal bloom or any other adverse conditions appear in the pond.
When the grass carp is stocked, duck weeds (small floating weeds like Wo/ffia, Lemna and Spirodella) need be introduced in required quantities as food. The duck weeds are preferably introduced within a bamboo enclosure in one side of the pond. The quantity of weed is regulated according to consumption by grass carp.
Algal bloom control
Fertilization, at times, may result in the development of excessive microscopic plants which are less desirable or may even become undesirable when they form bloom. Depending on the intensity of such blooms, Diuron @ 0.1 to 0.3 ppm
(1 to 3 kg per hectare-metre of water) may be used as control measure. The required quantity of herbicide may be mixed with water and spread uniformly over the pond surface. However, bloom in such small ponds are most conveniently controlled in about a week by thickly covering the water surface with duck weeds. The weeds may afterwards be removed from the pond. If grass carp existiSin the system the same will serve as their food and thus need not be removed
The growth and well being of the growing fry during the rearing period need be periodically checked. This is conveniently done by drag netting. Healthy fingerlings of 100-150mm size are obtained in three months rearing period Supplementary feeding is stopped a day before the date of catching. Harvesting is done during cool morning hours by repeated drag netting. Survival of about 70-90% (average 80%) is generally obtained in about 3 months rearing
- Central Inland Fisheries Research Institute, Barrackpore