Breeding of common carp

a. Natural breeding:

• Common carps differ from Chinese and indigenous major carps in their ability to breed naturally in ponds provided that some aquatic vegetation is available for attaching its adhesive eggs and that environmental conditions are favorable.
• A partially covered bottom with aquatic vegetation and a temperature of 18-22⁰C is suitable for spawning.
• However, this method could cause uncontrolled breeding causing high mortality among eggs, hatchlings, and fry due to sub-optimal attack of predators, unsuitable temperature, or contamination of fungi from dead and unfertilized eggs.
• To prevent this uncontrolled reproduction, they are either bred in a semi-controlled manner or a controlled manner by hypophysation.

b. Semi-induced breeding:

The decisive natural conditions to bring about spawning in common carp are as follows:

I. Suitable water temperature ( 18-22⁰C)

ii. Spawning substrate (Kakaban)

iii. water saturated with dissolved oxygen

iv. Slowly rising water level.

v. Presence of opposite sex

vi. Absence of other fishes especially carnivorous fish.

• Since the eggs of common carp are adhesive, the egg collectors called kakaban are positioned in the pond.
• The Kakaban is a mat-like structure made of dry grasses, pine tree branches, beaten palm bark, or leaves fixed on a frame.
• Generally, Kakaban is a rectangular structure having a length of 1.5-2 m and 1 m in width.
• For Spawning, the Kakabans are fixed about 20-30 cm below the water surface, propped upon bamboo/ wooden sticks.
• Under suitable conditions, One or two sets of spawners, each set consisting of one female and two males are introduced in the spawning pond.
• A gentle flow of water is maintained in the spawning pond after the brood fish are released. This triggers vigorous spawning.
• Generally, the female fish begin to investigate the spawning substrate and release her eggs scattering on it.
• Breeders are put in the evening and spawning is over by the next morning.
• After spawning, breeders are removed and the kakabans covered with eggs are transferred to nursery ponds for hatching.
• About 100,000 eggs are obtained per kg of female and about 80% of the eggs are fertilized.
• Fertilized eggs look dirty yellow which is different from damaged and dead eggs which look opaque and white.
• Hatching occurs in 46-48 hours at 28-31⁰C, 70-80 hours at 20-22⁰C, and evenup too 144 hours at 18-20⁰
• Thrust-hatched larvae attach to walls or kakabans using their cement glands.
• When the yolk sac is absorbed, they become free swimming and begin to feed.
• Transferring to rearing ponds may be done after 3 weeks.

c. Induced breeding

• Done by hypophysation.
• Done if conditions are not favorable for natural or semi-induced breeding.
• Ripe female common carp are first anesthetized by inserting in the mouth a sausage made of cotton wool dipped in MS 22 (0.5 g/50 ml of water).
• The vent is then sutured with waxed cotton thread to prevent inadvertent discharge of eggs.
• 5-3.7 mg/kg PG extract is injected to breeder fish.
• The male spawner receives only half the dose of the female and is kept separately.
• The abdomen is squeezed and eggs are collected.
• The milk from the male is then poured onto the eggs.
• For every liter of eggs, 2-3 ml of milt is needed to ensure fertilization.