3. 3. Breaking of the parasite chain
4. Better conditions for growth
and survival
5. Out of season supply of fry
and fingerlings
6. Production of superior strains
4. The artificial intervention in this
procedure consists of:
(a) collection of eggs, larvae or fry
(b) their protection from natural enemies
and unfavourable environmental
factors
(c) raising the larvae up to the fingerling
stage
(d) distributing them for stocking in
different water bodies.
5. Steps in artificial propagation
1. capture of wild brood fish from
spawning grounds,
2. selection of breeders from wild stock
for natural spawning or for hormone
treatment,
3. rearing of brood fishes,
6. 4. inducement of natural spawning with or
without hormone treatment,
5. procurement of ripe sexual products by
stripping with or without hormone treatment,
6. artificial fertilization,
7. incubation and hatching of eggs, and
8. rearing of larvae, fry, and fingerlings.
7. Brood fish
are sexually ripe fish
they can either be :
- collected from natural waters
just prior to the spawning
season
- collected from spawning
grounds
- raised on farms
8. Farm rearing of brood stock
-Widely practised all over the
world
-It enables the building-up and
selection of healthy breeders
for eventual stock
improvement
10. 1.Temperature
it is advisable to rear the brood
stock in a pond where extreme
fluctuations of temperature do
not occur
Generally, warmer environment
accelerates gonadal maturation
11. 2. Light
The requirement for illumination
varies with different species.
Many fishes are irritated in
illuminated environments
12. 3. Oxygen
Frequent fluctuations and low
levels of oxygen content in pond
water tend to inhibit gonadal
development
13. Fresh, oxygen-rich water, is an
important requirement during the
rearing of brood stock.
14. 4. Tranquillity
It is believed that frequent
disturbances interfere with
normal gonadal development
15. 5. Stocking density
Although most cultivated fishes
are able to tolerate crowded
pond conditions, the effects of
crowded conditions on gonadal
development is often deleterious
16. In general it is not advisable to
stock would-be breeders along
with market-destined fish,
especially if the latter are fed an
unbalanced diet.
18. 6. Size and depth of pond
The rearing pond for larger
brood fish (2–10 kg or above)
should be about 2 000–4 000
m2. Smaller brood fish can be
raised in smaller ponds.
19. The depth of brood fish ponds
generally varies from 1 to 2 m.
20. 7. Food
A suitable and adequate food
supply is of foremost importance
to brood fish.
21. If the fish are left hungry or
starving, the vitellogenesis
phase of egg development is
affected.
22. If the food is deficient in
essential nutrients, particularly
the amino-acids, vitamins, and
minerals, the egg development
is adversely affected, ultimately
leading to the failure in
ovulation.
23. Breeders reared on ample
natural food or on a protein-rich
artificial diet yield satisfactory
results.
24. It is better to breed a smaller
number of brood fish on
qualitatively and quantitatively
satisfactory diet (or natural food)
than to keep a huge stock under
half-starved conditions.
25. Age and weight of the
breeders.
The “first spawners” or “virgins” are
usually used for artificial
propagation.
Larger fish produce more eggs,
but the handling of “giants”
weighing over 10–15 kg is rather
27. The symptoms indicative of the
ready-to-spawn condition
Females:
Well-rounded and soft abdomen, the
fullness of which extends posteriorly
past the pelvis to the genital opening.
The genital opening is swollen,
protruding, and reddish or rose in
colour; its edge is uneven or fringed.
28. The anus (vent) may also be swollen
and reddish.
In some column-living fishes, the
abdomen becomes red coloured.
Some fishes develop a nuptial colour
before ovulation.
29. Males:
The male releases a few drops of thick milt
when its abdomen is pressed slightly.
In some male fishes (Chinese carps and
Indian major carps) the dorsal surface of the
pectoral fin becomes rough.
Some male fishes of the Orinoco and
Amazon basins produce a sound when
taken out of the water.
30. Methods of Inducing ovulation
and/or spawning
1.Simulation of suitable environmental
factors
2. Administration of gonadotropic
hormones
3. Combination of the two methods
31. Some pond spawners can be
stimulated to spawn by
providing:
1. nests
2. artificial spawning surface
(Kakabans-mat-like
structures measuring a few
m2 in area)
33. Decisive natural conditions to bring
about spawning in common carp:
•suitable water temperature (18 –
22 C),
•grass-bottomed spawning ground
•water saturated with dissolved
oxygen
•slowly rising water level
•presence of the other sex
•absence of other fishes
34. Hypophysation - “short cut” of the
natural process
- gonadotropic hormone
extracted from the
pituitary of some other
fish (donor) is injected
into the breeder and
brings about final
ovulation
35. Limitations of Hypophysation
1.Some of the sensitive fish cannot
tolerate the treatment
2.Other fish may ovulate only irregularly
3.Breeders whose ovaries have not yet
reached the adequately ripe stage fail
to respond to hypophysation
4.Varying contents of gonadotropin
hormone in the pituitary gland
36. Dosage
• it is generally difficult to fix the exact
dosage, with the result that generally more
hormone than required is injected into the
breeders
•hormone dosage required can vary
significantly from fish to fish of the same
species and from technique to technique
•dosage actually depends on the
“readiness” of the females; their age, size,
sensitivity and many other factors
37. Total dose
2.5 – 3 mg (1gland) – hypophysis
required per kg weight in the case
of large breeders weighing over 5
kg
38. 1.5 mg (0.5 gland) -
hypophysis required per kg
weight for medium sized fishes
(2–5 kg)
0.75 mg (0.25 gland) -
hypophysis required per kg
weight for small fishes (0.5–2
kg)
39. •It is advisable to avoid
overdose in preparatory
injection, since it may lead to
partial ovulation, thereby
upsetting the normal schedule
40. 1. Single, full (100 percent) or knock-out
dose - is given when the breeder has been
in the resting phase for a long time
2. Multiple doses
2.1 preparatory dose - is about 10
percent of the total dose.
2.2 decisive dose
41. The males, as a rule, are only given
one dose of hormone, usually at the
time when the females are given the
last decisive dose.
It is important that the males are not
administered the hormone earlier,
since that may result in releasing the
sperm before the females are ready to
ovulate.
42. The dosage of gonadotropin
hormone extract is expressed:
1.in milligrammes
2.as a number of acetone-dried
hypophysis glands – gland unit
43. The acetone-dried pituitary
gland of a 1.5–2 kg common
carp weighs 2.5–3 mg.
This size of hypophysis is taken
as a unit, when the dosage is
expressed in terms of number
of glands.
44. Solvent
The solvent used for
gonadotropic hormone is
0.6–0.9 percent NaCl
(common salt) solution
45. The solvent is prepared by
dissolving 7 g (.7%)of clean
common salt, free of
iodine, in 1 l of boiled and
already cooled drinking water
47. 3. Addition of a measured
quantity of solvent to dissolve
the pituitary gland (10-30
mins)
48. Choice of body part to
inject
1. Intramuscular
2. Intraperitoneal
3. Intracraneal
49. •The fish becomes more
quiet if its head is covered
with a piece of cloth. It is
advisable to use towels
while handling breeders
and not to touch them with
bare hands.
50. •While injecting scaly
fishes, it is necessary to
take the precaution of not
pricking them through the
scales, but to insert the
needle beneath the scale
and prick through the
underlying muscle
52. •If temperature is too low,
ovulation takes a very long
time, or in most cases
becomes inhibited. High
temperature not only causes
higher oxygen demand and
rapid metabolism, but also
has its own inhibitory effect.
53. •The pituitary treated fish needs
about 50 percent more oxygen than
before the treatment. The
excitement caused by handling and
treatment also results in enhanced
oxygen consumption. It is,
therefore, essential to keep the
treated breeders in a well aerated
environment or in clean, oxygen-
rich flowing water.
54. •Disturbed fish become agitated,
swim rapidly and jump against
the wall of the tank, thereby
exposing themselves to injury.
Their tranquillity can be secured
by putting dark floating objects
on the surface of the tank where
the treated breeders are kept.
55. “Hour-grade”
The temperature of water in the
tank in which the breeders are
held is measured every hour
after the last decisive injection
up to full ovulation. The readings
are added to arrive at the hour-
grade.
56. •A knowledge of hour-grade
value would help the fish
farmer to know exactly when
to expect ovulation after the
last injection.
57. The hour grade value depends
on:
1.the fish species treated
2.the type of treatment
3.the size of the female
4.whether the fish starts
spawning immediately after
ovulation or not.
58. (a)Hour-grade in relation
to fish species
At a temperature of 21 –22 C,
the hour-grade of common carp
is 240–260, while that of grass
carp, silver carp, and bighead
is 200–220.
59. (b) Hour-grade in relation
to the type of treatment
•The hour-grade is 340–
360 in the case of
common carp, when only
one decisive dose is
administered.
60. •It will be only 240–260 if
a preparatory dose is
given 24 hours prior to the
decisive dose.
61. •The hour-grade value
would go down further to
200–220 in cases where
two decisive injections are
given with an interval of
6–8 hours.
65. • In common carp, the
hour-grade value is
usually about 130–150
only when the breeders
are of small size (1.0–
2.0 kg).
66. d. whether the fish starts
spawning immediately after
ovulation or not
•When released with ripe active
males, most of the injected
females begin spawning in the
“ward basin” or “ward tank”.
67. •Failure to spawn would mean
that the species is not
responsive, the males are
inactive or already spent, the
females are injured or suffering
from an overdose of hormone, or
some of the environmental
factors are unfavourable.
68. “Induced spawning” or
“hormone induced
spawning” –spawning of
fishes that are treated by
gonadotropic hormone in the
presence of active males after
normal ovulation
70. Advantages:
1. There is no need to
calculate the exact time of
ovulation, or watch the
females to determine
whether they are ready for
stripping.
71. 2. It is not necessary to catch
the breeders for stripping,
thereby avoiding possible
injuries to the breeders.
72. 3. There is no need to strip
the breeders and fertilize the
eggs artificially, which
process is not only time-
consuming but would also
require more working hands.
73. 4. The danger of
over-ripening of eggs in the
ovary would not arise, since
the fish would start to spawn
as soon as ovulation is
completed.
74. Stocking density and Sex
Ratio
To achieve successful induced
spawning, it is advisable to put
together one female and two-three
males, two females and three
males, or a maximum of three
females and four males, depending
on the size of the ward tank.
75. In the case of breeders
weighing 2–3 kg each, a
maximum of two females
and three males can be put
in a ward tank of 2 m2.
76. As many as three-five
females and four-six males
can be put in the same tank if
they weigh only 0.5–1 kg
each.
77. If the breeders weigh 4–5 kg
each, the putting together of
only one female and two
smaller males is advised. Still
larger fishes would require a
larger ward tank to obtain
satisfactory results.
79. Fertilizing Solution
The fertilizing solution is
prepared by dissolving 30 g
carbamide (urea) and 40 g
common salt (NaCl) in 10 litres
of clean (preferably filtered) pond
water.
80. The quantity of the solution
to be poured on to the eggs
in the beginning is about 10–
20 percent of the volume of
the eggs to be handled.
81. The mixture is then stirred with
a plastic spoon or a feather for
about three-five minutes
continuously, during which time
one sperm enters an egg
through the micropyle and
completes the process of
fertilization.
83. About 2–4 litres of tannin solution is
placed in a plastic bucket and a
maximum of 2–3 litres of swollen
eggs may be added to it all at once.
After stirring for 3–5 seconds, clean
water should be poured into the
bucket. Once the eggs have settled
down, the water is drained out,
preferably by using a strainer.
84. Incubation and Hatching of
eggs
•Fertilized eggs should be
placed in the incubators not
more than 1 minute after
fertilization in the case of
untreated sticky eggs
