Wednesday, February 19, 2014

Hatchery Technology of Giant Freshwater Prawn

Hatchery Technology of Giant Freshwater Prawn

Macrobrachium rosenbergii is the giant freshwater prawn usually cultured in India.  It is euryhaline and eurythermal in habit, so it is a suitable candidate species for culture.  Macrobrachium rosenbergii matures when they are months old.  The female after a premating moult mates with a hard shelled male.  The fertilized eggs are carried by the female in a brood pouch in the ventral side of the abdominal region.  The fertilized eggs hatch out in 18 to 23 days.  The newly hatched larvae require estuarine water but it can survive in fresh water for three to five days.  The larvae after passing through many stages in estuarine region become postlarvae which then migrate to freshwater. 

Brood stock collection and hatching:
Female prawn carrying fertilized eggs in the abdominal pouch is called berried female.  It can be collected either from rivers or culture ponds.  While collecting, care should be taken to see that the eggs are not lost due to rough handling.  The berried females are transported with oxygen packing.  Hatching can be done either in larval tanks or in a separate hatching tank using freshwater or 12 ppt saline water.  Usually hatching of egg takes place during night hours.  The hatching period lasts for 3 or 4 days.  Major quantity of larvae is released on the second day of the hatching.  The newly hatched-out larvae can survive for about 5 days in fresh water.  After hatching the mother prawn should be removed from the hatching tank.  The larvae pass through 11 stages to become post larvae.  For collecting the larvae they can be concentrated at one portion of the tank by putting a light at the collection point after covering other parts with a black cloth or black sheet as they are very much attracted by light.

Feed and feeding:
Feeding of larvae starts from second day onwards.  Artemia is the most ideal and widely used feed for larval rearing.  Artemia is a small crustacean seen in hyper saline water.  Its eggs are collected, packed and supplied by several companies.  The cysts are hatched in separate tanks and the hatched out naupli are fed to larvae. 

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