Previous - Next
Broodstock management covers three particular aspects of the rearing process:
(a) The selection of fish with desirable hereditary
qualities typical of improved strains such as rapid
growth potential, higher resistance to dissolved oxygen
deficiency and adverse water quality, strong appetite, omnivorous
feeding regime. (b) The selection of fish with
well-developed sexual organs.
(c) The rearing of these selected fish to
produce healthy potential spawners, with dormant eggs well
developed in the females.
38. What is the basis on which to select good future breeders?
The selection of future carp breeders should take into account the general shape of the fish body, scale distribution, state of health and development of sexual organs. In particular,
(1) the selected fish should be in good health,
(2) with no body wounds,
(3) no parasites,
(4) a typical scale distribution, and
(5, 6) no fin or body deformation.
(7) The body should possess the required shape and proportions,
being neither too fat,
(8) nor too thin.
39. How can the difference between male and female carp be determined?
Male and female breeders may be easily differentiated by the shape of the body and the relative position of the genital papilla. In females, the body is plump and the genital opening is situated above the genital papilla. In males, the body is slender and the genital opening is found behind the genital papilla.
40. What are the external signs of the breeder's maturity?
To check whether a carp breeder has reached maturity (presence of dormant eggs or sperm) and may be selected for artificial propagation, the belly and genital papilla should be examined carefully.
A mature female has a well-rounded and soft or semi-soft belly; its genital papilla is erect and reddish; its anal opening is enlarged and protruding.
A mature male will release milt under a slight abdominal pressure; its belly is not blown up but rather slim; it sometimes has callosities on the head.
41. Broodstock ponds are 0.5-1 train size end 1-2m deep.
The dikes should be protected by vegetation. Water control structures exist at the inlet and outlet of the pond. Access by road and good protection against poaching should be ensured. The stocking rate varies from 100 to 300 breeders per hectare.
42. Broodstock management is one of the most important elements of the hatchery production system.
In temperate climates, the spent spawners leave the hatchery in late spring. They are given a quick salt bath (2-3% salt solution, for 30-40 seconds) against ectoparasites (1) and they are stocked in broodstock ponds where they are well fed during summer and autumn (2).
Overwintering takes place in the same pond. The following spring, the breeders are seined out of the pond (3). They are sorted by qualified personnel who select the good potential breeders and separate them by sex. The other fish are marketed.
The selected breeders receive a quick salt bath and are stored in storage ponds, the sexes being kept well separate (4).
When the reproduction season starts in mid-spring, the breeders are seined out of the storage ponds as necessary; those which are mature are chosen, receive a quick salt bath (5), and are then stored in the hatchery where they will be propagated artificially a few hours later (6).
(A) Females and (B) males are preferably kept in separate broodstock ponds.
Two sets of ponds are used for the ripening males and females, and two sets of ponds are used for the spent spawners. This wild prevent wild spawning. It will also enable higher protein feeds to be distributed to the females, and to lower the stocking rates.
About 200-400 ind/ha is sufficient to control the wild fist which might enter the pond and compete for food with the broodstock.
Similarly, these carnivorous fish will eliminate the juvenile' born from wild spawning.
45. Broodstock feed varies according to the season.
(2) After stripping, when the breeders form new eggs which develop toward the dormant stage, they should eat a mixture of 50% natural food organisms rich in protein and 50% artificial feeds with a high content of carbohydrates, such as maize.
(1) Later, when the dormant eggs have been developed and when the breeders await spawning, they should receive artificial feeds with a 30-40% protein content in order to prevent the accumulation of fat in their gonads.
A skilled worker selects the breeders one by one: mature breeders are brought into the hatchery building (1), immature breeders are put back into the storage pond (2), and unhealthy or invalid fish are sent to the market (3).
This selection process is especially important for the females, whose maturity should be thoroughly checked, to ensure the success of the artificial propagation.
During handling, fresh water may be pumped into the crowded enclosure if necessary.
48. It is best to handle carp breeders using a special net with a strong mesh.
It should be open at both ends, the stiffened mouth opening measuring about 30 cm in diameter and the netting 1 m long. A breeder may easily be caught in it (2) and transported with two hands (3). When the end of the net is released, the fish can swim out easily (4).
Broodstock transport may also be mechanized, using fibreglass containers and compressed oxygen as detailed in the next picture.
The fish are introduced through the top door and removed through the back door.
Compressed oxygen is delivered in fine bubbles from the bottom of the tank through a perforated plastic tube attached to a metal frame.
In such a tank 20-30 carp breeders per cubic metre of water can be safely transported for journeys of up to several hours.
