Multiple Breeding

Carp seed production is no more confined to monsoon months. Now a days carps have been domesticated to breed much ahead of monsoon and months beyond the monsoon, ensuring the seed during pre and post monsoon periods. Such availability of carp seeds promises success in intensive carp culture practices. It also can compensate the loss of seed due to the natural calamities like flood and draught etc. surprisingly the brood involved in pre-monsoon are not different individuals but one and the same as professional brood.

Pre-monsoon Breeding: Success in Pre-monsoon breeding depends on a precocious gonad maturity. This can be achieved by simple brood stock management practices. Pre monsoon breeding commences as early as March. The yield is 0.5 – 0.6 lakh spawn/kg body weight of fish. Second spawning of same fish is achieved with in a time interval of 40 – 45 days. The production rate increases to 1.0 – 1.5 lakh spawn/kg body weight. Both the spawning are completed between March & May.

Monsoon Spawning: A time lapse of another 40-45 days following the second spawning brings the 3rd crop (June-July). During this period climatic conditions are more favorable than any other breeding period and they yield further increases to 1.5 – 2.0 lakh spawn/kg of body weight.

Late Monsoon Spawning: Quality of mature eggs can not be maintained in situ for indefinite period. Therefore, monsoon dependant traditional broods are not useful for late monsoon breeding. This is possible only to spawn when the same fish repeatedly with an optimum time interval between two successive spawning. The fish has already spawned two or three times in a seasons expected to come for late monsoon breeding i.e. between August & September. However, the yield of spawn declines when compared to monsoon breeding.

Principle of Multiple Spawning: Multiple spawning is the timely harvesting of mature gametes repeatedly by more than two spawning. The fishes are bred by adopting routine hypophysation technique. Major carps have been bred as many as four times between March and September. Brood recovery I to II and II to III within the stipulated period (March – August) is observed almost 100%. Further re-maturation rate declines 30 – 50% which may need some more management manipulation for the purpose.

Brood Stock Management and Multiple Breeding:

Gupta et al (1990) reported advancing maturity spawning of Asiatic Carps during April & May through brood stock management. Futher maturity could be preponed by following improved management practices for which spent brooders of proceeding breeding season are preferred as the initial stock for the programme. However the age of the fish should be 2 to 3+ years stocked at 1000kg/ha. They are fed on formulated protein rich feed fortified with vitamins and minerals at 1-2% of their body weight. As water replenishment has a considerable impact on gonadal maturity of fish, it should be done twice a month preferably with fresh canal/reservoir water from February to May. Other management practices are of routine nature. Such managed brooders show precocious gonadal maturity at least three months earlier than monsoon dependant in the locality.

Breeding Status of Multiple Spawners:

Type of brood raised for such multiple spawning is termed as professional brood. These broods certainly spawn early and show better breeding response as compared to brood maintained for monsoon dependant traditional breeding. The brood 4 – 5+­­ years of age show consistent yield of spawn. Therefore, it is essential that the overage fish should be excluded from the multiple broods, rearing programme. Further, to build up a stock of professional brood is a continuous process for successive multiple spawning programme.

Care of Multiple Breeding:

Spent brood monitoring programme is an important aspect better survival and recovery of the spent brood, most care is suggested at every stage for handling as follows.

· The brood should be transported in the canvas bags along with water
· Hormone administration should preferably be intraperitoneal which reduces the stress of injection.
· Stress should be minimized in spawning pool by providing required flow and duration of water supply in the pool for spawning.
· Spent brooders should be removed from spawning pool as soon as breeding operation is over.
· Spent brooders should be treated at regular intervals with potassium permanganate solution (5 ppm). This keeps a check on secondary infection and also quickens recovery from spawning stress.
· Feeding and other management practices should be followed meticulously for subsequent maturity.

Larval care:

The performance & Survival of spawn produced through multiple breeding are comparable to that of traditional seed. However, spawn produced through multiple breeding need special care as the yolk gets absorbed within 60 hrs of fertilization. So food is essential after 60 hrs of fertilization. The food may be micro-plankton or particulate materials suspension.

Conclusion:

It is possible to produce seed during pre-monsoon, monsoon and late monsoon in a calendar year. A cumulative yield of spawn per kg body weight of fish is enhanced to 3 – 4 folds than single breeding. Further cost of seed production is reduced. It also provides opportunity for multiple cropping in aquaculture practices.