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

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are Pulicat lake, Godavari, Mahanadhi estuaries, Chilka lake and Hoogly
- Matlah estuary (Gopalan and Purushan, 1981).
In aquaculture concept, nurseries are well prepared small
enclosures where favourable physico-chemical and biological conditions
are provided for the maximum survival of shrimp fry. Usually size of
nurseries varies from 50-200 m’ and 0.5 - 0.6 m deep. The well
prepared nurseries generate natural food organisms promoting growth
ofsfiuinm>fry.In nurseries post larvae collected fro nature or procured
fran hatcheries are provided with condition similar to estuaries. A.
matter of concern in the hatchery and nursery is the availability of
proper larval feed organisms such as phytoplankton, Artania, Rotifer
(:B_,rach_i,onu_s sp) water fleas (§1_o_i_n_a _s_p), copepods, marine yeast etc.
Also attempts to make artificial feed for rearing larval shrimps were
made (Hameed Ali and Dwivedi, 1990).
Post larvae of_§. indicus (9-15 mm) and those of_§. monodon (8­
25 mm) attained 40-70 mm size in 30-60 days when reared in nursery
ponds under densities of Z-6 lakh/ha giving a survival rate of 30-70%.
The survival rate varied with the stocking densities. At Kakdweep in
West Bengal, 85.5% survival rate was obtained with a higher density of
28,500An‘. Post larvae of B. monodon and Z. indicus (12.5-13.74 mm)
reared in nylon cages at Kovalam (Tamil Nadu) using fresh clam meat in
15 days gave a survival rate of 60-90% uder densities of 200-500/m’
(Siddharaju et al., 1980).
The shrimp post larvae from estuaries or hatcheries when
directly transferred to stagnant ponds where peculiar ecological
conditions exist are likely to undergo mass mortality. It is to evade
the chances of such a possibility that the post larvae are carefully
reared in well set nurseries for a period of 2 to 3 weeks before they
are introduced to advanced nursery system or stocked directly to the
grow out pond. Earthern nursery ponds range an area from 50 to 200 m’
with an average depth of 40-70 cm. The larvae stocked at the PL9-PL10
stage at densities of 100-150 per ml can be reared in such ponds upto