studies on improved practices of prawn farming for higher ...

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The market size shrimps are caught three to six months after
the juvenile shrimps are stocked in the grow out ponds. China produces
one crop per year (Fwy-October), semi-tropical countries produce two
crops per year, while farms close to equator can produce three
crops/year when all other conditions are favourable.
Semi-intensivefimanagement
Of the different levels of management developed by researchers
for raising shrimps to suit varying pond. conditions and financial
capabilities, semi-intensive farming is one option that pond operators
may find appropriate for their resources because it requires less
capital than intensive culture.
Semi-intensive farming is practised in carefully laid out farms
above the high tide line to the extent of 90% in China, 50% in Japan,
60% in Taiwan, 40% in Philippines and 25% in Thailand. Ponds for semiintensive
farming requires excavation of peripheral or diagonal canal
at 10-15 m wide and 50-100 cm deep and the installation of drain and
supply gates for each copartment. These are needed to protect the
stock from drastic temperature changes and to provide shelter during
moulting. In addition, gates are required in opposite corners one for
water supply and other for water drain. Pond size varies from 2 to 25
ha. Exchange of water expected is 10-20% if possible using a pump.
Water management aims at maintaining water at 70-80 cm at the pond and
120-130 cm at the canal portions.
Predation is prevented by using effective filter devices.
Organic pesticides such as derris root E tobaco dust and inorganic
chemicals such as amonium sulphate and sodium hypochlorite in required
doses are used to control the pests.
Fertilization to stimulate the growth of natural feed is done
by applying inorganic fertilizers like ammonium phosphate and urea in
the ratio 3:1 along with lime. The organic matter of the soil can be