International Journal of Aquaculture, 2018, Vol.8, No.12, 90-97
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2.2.2 Stocking density and ratio
According to Sinha et al. (1985), a pond having average water depth of 2.0-3.0 m may be stocked at the rate of
5,000 fingerlings/ha. However, Datta (2014) advocated 6,000-12,000 fingerlings/ha in pond having an average
water depth of 2.5 m. In any case the principle behind determining the stocking ratio is to fulfill the habitat and
feeding niches operating in the upper, column and bottom layer of the pond with species combinations in such
away to minimize overlap. However, for formation of distinct three layers in pond ecology a minimum depth of
six feet is required. Generally, in six species combination, the upper layer of the pond is stocked with 30% of the
total stock, whereas, the column and bottom layer holds 40% and 30% of the stocks respectively. Again, in each
layer one IMC is co stocked with one exotic carp with non-competing habits e.g. catla with silver carp (upper
layer), rohu with grass carp (column layer) and mrigal with common carp (bottom layer). Alikunhi et al. (1971)
advocated production levels ranging from 3,000-3,500 kg/ha/yr, with a stocking density of 3,000-3,500 nos./ha.
Nearly 75% fish farmers in North 24 Pgs. district, West Bengal, practice 7-12 fish species at stocking density
above 15,000 nos./ha in their ponds without maintaining the specific ratio (Biswas et al., 2017).
2.3 Post-stocking management
2.3.1 Feeding of fishes
Commonly available agricultural by-products such as rice bran (60%) and mustard oil cake (40%) are used as
supplementary feed at the rate of 3% of standing crop of fish. Feeding of fish at 2-5% of the body weight is
recommended based on natural productivity of fishpond (Sarkar, 2002). The recommended feeding rate is 5-6% of
the body weight upto 500 g size of fish and then reduces to 3.5% of body weight from 500-1,000 g size of fish
(ICAR, 2014). According to Biswas et al. (2017) most of the farmers (79%) in 24 Pgs. (N), West Bengal provide
supplementary feed @ 7.5% of the body weight up to 500 g size of cultured carps and @ 4.6% of the body weight
of 500-1,000 g.
2.3.2 Fertilization and liming
Raw cow dung @ 1,000 kg/ha/month can be applied near the dyke of the pond. Organic fertilizer like urea can be
applied @ 25 kg/ha/month and single super phosphate @ 20 kg/ha/month. Inorganic manure is normally applied
after 15 days of application of organic manure. Liming should be done once in a month @ 25 kg/ha to correct the
water pH. Vermicompost might be a cost-effective fertilizer in carp culture, replacing the expensive chemical
fertilizer di-ammonium phosphate (Chakrabarty et al., 2008). Now majority of the fish farmers (81.76%) in 24 Pgs.
(N), West Bengal apply fertilizers viz. single super phosphate and urea for enhancing productivity during post
stocking management of carps with no scientific basis with regards to frequency and dosage (Biswas et al., 2017).
2.3.3 Health care and hygiene
The health of fish in ponds depends mainly on the environmental conditions and the skills of the farmers.
Accordingly, the water quality, feeding and the intensity of production are the factors which determine the actual
health condition of fish (FAO, 2010). Before releasing the fingerlings, a dip treatment with 3% KMnO
4
for
1 minute should be given. Alternatively 2% to 3% common salt solution may also be used. In case of any parasitic
infestation like Argulus sp., Malathion @ 0.25-0.5 mg/L 3-4 times at weekly interval can completely eliminate the
parasite. Test netting must be carried out periodically for ensuring growth and health status of the cultured fishes
once in a month. Checking the growth of fish should be done on a regular basis, preferably once in two months
(FAO, 2010).
2.3.4 Harvesting and yield
Harvesting is generally done at the end of first year, when the fishes attain average weight of 800 g to 1.25 kg.
With Proper management a production of 4 to 5 tonnes/ha can be obtained in a year (ICAR, 2014). Fish
production obtained by combined culture of IMC and exotic carps was 2.06 tonnes/ha/yr (Hussain et al., 2013).
Fish farmers produce above 5 tonnes/ha/yr at stocking density above 15,000 nos./ha and with more than one or
two stocking frequency (Biswas et al., 2017). Moreover, the original practice of complete harvesting at the end of
one year production cycle was mostly abandoned with multiple socking and multiple harvesting concepts in recent
years.
