Ch10

Whenever possible, hypophyses (pituitary glands) should be collected from mature, freshly killed carp. They should then be dehydrated and stored. These dried hypophyses will be needed for the preparation of the hormonal extract to be injected into the carp breeders for inducing their maturation.

104. To remove the hypophysis from a freshly killed carp, (1) in electric drill with a special drilling head may be used.

The head of the fish being firmly held vertically between two pieces of wood, proceed as follows: (a) draw a line perpendicular to the lateral side of the head from each eye; (b) place the centre of the drill at the meeting point of these lines; (c) adjust he drilling angle so that it equals 90°; (d) drill through the top of the skull, the brain and the base of the skull, down to the mouth cavity; (e) take out the drilling head together with the small cylinder made of bone and tissues. (2) Using a wooden finger fixed to the table, remove this cylinder from the drilling head. 3) Cut it in two, carefully lift the brain tissue (including the hypothalamus) lying on the base of the skull, and pick out the hypophysis with a forceps.

Place it in a bottle containing acetone, together with the other hypophyses collected on the same day.

105. Before storage, (1) hypophyses (2) are dehydrated in acetone for three periods of eight hours each. New acetone should be used at the beginning of each period. (3) At the end of this treatment, the hard hypophyses are dried on blotting paper. (4) They are then placed in small glass containers and pressed down with a ball of fine cotton.

These containers should be tightly sealed, using for example wax or paraffin. A label should be added, indicating the date of collection and the origin of the glands. Even in tropical regions, acetone-dried hypophyses can be stored for at least 5 years without refrigeration. The sealed containers should be kept either in a plastic bag or in a desiccator, in the presence of a water absorbent such as silica gel or calcium chloride.

TABLE 1. SELECTED DATA ON THE REPRODUCTIVE BIOLOGY OF COMMON CARP

First sexual maturity
		Temperate climate		Warm climate
Age, years	Males	2 - 3		1
	Females	4- 5		1 - 2
Weight, kg	Males	3 - 4		-
	Females	4- 5		-
Standard length, cm	Males	25 - 30		15 - 20
	Females	30 - 40		15 - 20
2. Spawning
Spawning water temperature, °C			at least 17
Optimum range temperature, °C			22 - 24
Spawning behaviour			in groups, in fully inundated grassy areas
3. Egg stage
Ovulation period in hour-grades (°C)			240 - 260
Incubation period in day-grades (°C)			60 - 70
Number eggs per kg carp body weight			100 000 - 200 000
Number dry eggs in one kg			700 000 - 1 000 000
Number swollen eggs in one litre			80 000 -120 000
Diameter of dry eggs, mm			1 - 1.5
Diameter of swollen eggs, mm			2 - 2.5
4. Larval stage
Total length newly hatched larvae, mm			4.8 - 5
Duration larval stage, day-grades (°C)			60 - 70
5. Early fry stage
Total length early fry at first feeding, mm			6 - 7
Size at first food, mm			0.1 - 0.2

TABLE 2. SELECTED DATA ON THE ARTIFICIAL PROPAGATION OF COMMON CARP IN A HATCHERY

1. Broodstock management
Pond size: 0.5 - 1 ha
Stocking rate: 100 - 300 inc./ha

Feeding:
(a) during formation of dormant eggs: 50% natural food and 50% artificial feeds rich in carbohydrates.
(b) after formation of dormant eggs: artificial feeds containing 30-40% protein.

2. Production of sexual products, milt and eggs
Water temperature, °C	20 - 24
Sex ratio of breeders	2F:1M
First injection of females,
dried hypophysis mg/kg	0.3
salt solution ml/fish	0.1
Second injection of females,
dried hypophysis mg/kg	3.5
salt solution ml/fish	1.5
Single injection of males,
dried hypophysis mg/kg	2.0
salt solution ml/fish	1.5
Time between two injections of females, hours	10 - 12
Time between 2nd injection females and ripening,
hour-grades °C	240- 260
Minimum time necessary after injection males, hours	6
Percentage of ripening females	60 - 90
3. Artificial fertilization of the eggs
Quantity of milt necessary, ml/kg dry eggs	10
Percentage fertilization success	80 - 95
4. Incubation of the fertilized eggs
Water temperature, optimum °C	22 - 24
Quantity of eggs in 7-litre jar
e.g. dry eggs, kg	0.25 - 0.30
swollen eggs, litres	1.5 - 2
Water flow, litres/minute	0.6 - 2
Duration of incubation period, day-grades °C	60 - 70
Malachite-green treatment, cone. mg/l.	6
Percentage hatching success	95
5. Rearing of larvae and early fry
Water flow, litres/minute	12 - 15
Number of larvae in 200-litre jar	500 000
Duration of yolk-sac stage, day-grades °C	60 - 70
Duration of rearing in jar, days	3-4
Percentage survival rate	60 - 90
Number of early fry produced/kg dry eggs, thousands	500 - 700
Size of first food, mm	0.1 - 0.2

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