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Grow-out Culture
The pearlspot is suitable for culture in confined, fresh and brackishwaters. The
fish is cultured on a small scale mainly in the state of Kerala. It is cultured
in the traditional manner, in the 'Pokkali' fields (paddy fields). An annual yield
of 3 to 5 tonnes is obtained from these fields, of which, prawns constitute 80%,
while the mullets and pearlspot form 20%. In mixed-culture operations along with
prawns and other fishes ranged from 768.2 kg/ha/3 months at a stocking density of
25,200/ha (24000 prawns + 1200 fish) to 845.4 kg/ha/110 days at a stocking density
of 20,300/ha (20,000 prawns + 300 fish) have been reported. The culture of pearlspot
is more economical under polyculture system especially with milkfish and mullets
than under monoculture.
The fish can attain a marketable size of 120-150 g over a period of 8-10 months.
Though growth rate is relatively slow, high stocking density with low input management
can yield optimum production. Under monoculture at stocking densities ranging from
20,000 to 30,000 / ha, an average production of 1,000 kg/ha/year can be obtained
in brackishwater ponds. The fish can also be reared in the backyard ponds and tanks
in the rural areas. Being a herbivorous fish it is suitable for polyculture. Pearlspot
farming could be adopted to any scale integrating with other occupations like poultry
farming. The poultry droppings form good manure for natural food production in the
culture ponds.
Adult fish in the weight range of 50-125 g are stocked in ponds @ 5,000 nos./ha.
The fish are fed with supplementary feed @ 3.5% of the body weight (prepared with
groundnut oil cake 40%, rice bran 45% and fish meal 15% fortified with vitamin and
mineral mix @ 2.5 kg per 100 kg of feed). The feed is supplied in pellet or dough
form. The hydrographical parameters desirable for the breeding and seed production
of pearl spot are: water temperature 24-32°C, salinity 15-30 ppt, dissolved
oxygen > 3.5 ppm, pH 7.0 to 8.0 and transparency > 50 cm. To facilitate egg
attachment, the pond is provided with substrate materials such as palmyrah leaves,
coconut leaf petioles, coconut husks, wooden twigs, bricks etc. Breeding occurs
within 30-40 days of introduction of the brooders. A production of upto 6 lakhs
fry/ha/year can be achieved. Harvesting is usually undertaken by draining the water
from the ponds and operating a seine net, cast net or a drag net for capturing the
fish.
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