Seed production and culture of Pabda : A new avenue for income generation

Pradyut Biswas / Ramanuj Chakraborty *

Ompokbimaculatus, commonly known as Pabda is a native species and recently gaining its importance as a promising aquaculture candidate owing to its good taste, excellent nutritional profile and high market value.

It is also considered to be a species which can be diversified towards both species and culture system diversification. The species can thrive well in shallow water which makes them more preferred species to be cultured in seasonal water bodies of most of the North East part of India.

The species also can be made to ne smoked which is delicacy in NE states. The fish is remarkable because it can survive without food and water for some reasonable length of time. Unlike other catfishes the species is fairly peaceful and shy and goes well with carps.

But recently, the reduction in the habitat area as results of reclamation of wetlands coupled with c=excessive use of pesticides, herbicides and inorganic fertilizers in agricultural farms make the to be rare and identified as vulnerable to extinction.

In spite of having the potential as a good diversifies species, it has not received t=much attention in aquaculture mainly due to non-availability of information regarding its breeding and culture technique. Captive breeding can go a long way in diversifying this aquaculture species.

ARTIFICIAL BREEDING

Usually this species attains maturity at the age of one year and breeds during May-August. During breeding season, male and female pabda are well fed with feed containing 30% protein diet daily, at least 3 months prior to breeding season. Matured males have a rough first ray in the pectoral fin at the lower side and have a narrow and rather pointed genitalpapilla, which releases white milt if slight pressure is applied to the abdomen.

Females have a smooth pectoral find and the genital papilla has a thick muscular round opening. Before breeding the fished are caught from the pond and kept in the FRP tank for 10 hours for evacuating the ugts. After that the females are induced through hormone therapy using Ovaprim, Ovatide or OvaFH. The females are given the dose of 2.0-2.5 ml/kg body weight of fish and the male are given half of the female dose.

After injecting the fishes are again kept the same tank together. Eggs from ovulated females were stripped after 10-11 hours into rectangular plastic fertilization trays. Following ovulation, the testes were removed from the male fish and sperm was pressed into a sterile dry Pewtri dish. Stripped eggs were then fertilized with the diluted sperm suspension by mixing them with a feather.

Then the fertilized eggs were washed several times with fresh water to remove excess milt. Shining and brown coloured beads like adhesive eggs are considered as good eggs, while white coloured eggs are of bad quality. A 100 g female lays around 4,000-6,000 eggs.

An indigenous modified micro-hatchery has been developed at College of Fisheries, Lembucherra with 6 nos. of 500 L FRP tanks and 4 nos. of 500 L glass aquariums. The settled filtered pond water can be used for hatching the eggs.

For incubation the fertilized eggs are uniformly distributed in the specially made net baskets which are kept in glass aquarium. It will take 24 hours for hatching in temperature range of 27-30 degree C. The water level kept at a height about 14-15 cm.

The system can accommodate 15000-20000 fertilized eggs in one aquarium with 60-80% hatching rate. After hatching, the larvae will come out of the net basket and settled at the bottom corner of the tanks. After hatching the net baskets are taken out with egg shells remaining and washed with the KMnO4.

LARVAL REARING:

The larval rearing phases are the most crucial period for magur hatchery. Large scale mortality occurs during these development stages. 22 hours post-fertilization, the embryos hatched. The newly hatched embryo were5-6 mm in length with a small yolk sac attached. The larvae are reared in the same incubation tanks. There is no necessity to provide feed during first day as yolk sac in larvae serves as the stored feed.

After yolk sac absorption, the larvae are fed with either live plankton or Artemianauplii. Other live food such as fish flesh, earthworms, tubifex are also tried in live and freeze dried condition. It has been found thattubifex worms in live condition are most preferred by the larvae if these are given in finely chopped form. It is important to provide good environment to the larvae.

For the purpose the indoor rearing tanks are provided with continuous aeration and water exchange facilities. There is a chance of mortality and poor growth of larvae due to poor environment and high stocking density during in-door rearing phase. A stocking density of 1000-2000 nos./m2 is considered to be optimum for better growth and survival in indoor condition.

The larvae grow to 15-20 mm fry during 15-21 days of rearing. After a maximum of 21 days rearing in the indoor, they should be transferred to out-door rearing tanks for fingerling production.

The most important points to be kept in mind for undertaking pabda breeding in the hatchery are:

1. Always select good healthy brooders.
2. Choose the hormone dose according to the ripeness of brooders.
3. Always keep an eye on the size of food particles, particularly in larval rearing phase.
4. Use iron free water in the flow through system.
5. Remove/replenish fully or partially the water, excreta and unconsumed food materials from the larval and fry rearing tanks.
6. Feed the young fish properly with ost preferred food to avoid cannibalism.
7. Shed may be provided to reduce cannibalism.
8. Sort out bigger ones from the smaller one to reduce cannibalism.
9. Maintain hyge=ienic condition in the hatchery.
10. Always keep ready an electric generator as stand-by arrangement
11. Routine checking of different rearing systems.

REARING IN NURSERY POND: For nursing of fry 0.08 ha pond area was better. At first pond was dried completely and 5-10kg cow dung per decimal was given in the pond then after immediate tillage 250kg lime per ha was given and kept for 1-2 days. Then watering was done by shallow machine.

Frog, snake and other discarded animal was very harmful for nursing of fry. It is a must to give more attention to protect the nursery pond from being entering the frog, snake, etc. So small mesh sized net was used to surround the whole nursery pond.

5 days old fry was stocked into the nursery pond at the rate of 15000 fry per ha. 50% rice bran and 50% dried fish powder were mixed together and used as nursery feed at the rate of 20% body weight per day. They were nocturnal in habit and so feed was given 2 times at night. Fry was reared in the nursery pond for upto 40 days until the fry became 2 inch size.

GROW-OUT CULTURE: The earthen ponds/stone pitched ponds/cemented tanks are suitable for grow-out culture of pabda. Generally high density of 25,000-40,000/ha is recommended for culture of this species. Bigger sized fish (5-10 g) shows good survival and growth during culture.

The fishes are fed at the rate of 3-5% of their body weight with pelleted feed in the feeding basket placed in different places of the pond. The fishes attain an attractive size of 100-120 g within rearing period of 1 year. Productions of 1-1.2 tonnes can be achieved from one hectare of water area.

CONCLUSION: Although induced breeding of Pabda is not a difficult task but main problem lies within the fertilization, hatching success and early development of the fish. Large scale mortality occurs in the early developing stage after absorption of yolk sac.

Proper feeding and water management excels the seed production. In recent past culture of pabda culture was not taken up in confined water bodies since seed of this species was not available in adequate quantities. Even, no definite culture system was practiced for this species. But now a days farmers are interested to stock pabda along with the carps which gives the additional financial benefit to them.


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