Finfish Breeding and Hatchery Management

The double-walled hatching hapa

●It  is one of the traditional and common devices used to hatch carp eggs. 
● A hatching hapa consists of two separate pieces of hapas, the inner and the outer hapa
●The inner hapa is smaller and fitted inside the outer hapa
●The fertilized are released in the inner hapa
●Upon hatching, the newly hatched hatchlings wriggle out through the round meshes of the inner wall and collect themselves in the outer hapa
● Remove the inner hapa containing egg shells and dead eggs once the hatching is completed.
●The hatchlings remain in the outer hapa till the third day when they are ready for stocking in nursery pond.
●The outer hapa is made of markin cloth or any fine-meshed durable cloth, stitched in the shape of a rectangular trough, without any cover and provided with ropes at its 4 upper and bottom corners. 
●The size of the outer hapa usually is  2 x 1 x 1m.
●The inner hapa is made of round-meshed mosquito net cloth with the dimension of 1.75 x 0.75 x 0.5 m; rectangular in shape and provided with ropes at its 4 upper and bottom corners.
●The hapas are tied to bamboo poles and fixed in a pond or river margin or cement cistern or channel with clear, oxygen-rich circulated water, not having algal blooms.
●About 25-30 cm of the outer hapa should be kept above the surface of water to prevent entry of weed fishes, insects, etc.
●The haching of eggs takes place 14-20 hours after fertilization at a temperature of 26-31⁰ C.
●About 75,000-100,000 eggs can be hatched in a standard hapa if fertilization rate is over 75%.

Merits :
1. Useful for hatching relatively small  number of eggs
2. Separates egg shells from hatchlings very effectively

Demerits :
1. Water quality can not be controlled
2. Fish from outside can damage  eggs and spawn through the hapa wall by sucking
3. Recurring expenditure is high