This document discusses hatchery management and natural fish propagation. It provides details on criteria for selecting fish species for culture, including that they must be able to withstand the local climate, grow quickly, reproduce successfully in captivity, accept artificial foods, be desirable to consumers, tolerate high densities, and resist disease. The document also describes the natural propagation process, including the development of sexual products like eggs and sperm, factors that determine propagation habits, and the fertilization process. Hatcheries aim to artificially propagate fish on a large scale to provide stock for aquaculture.

1. Hatchery
Management

2. Hatchery – a facility where eggs are
hatched under artificial
conditions

3. Facts:
20,000 - total number of fish
species in the world
2,200 - total number of fish
species in the Philippines
of which,
100 species are commercially impt.

4. Fish Production Methods
1. Capture
2. Culture

5. Criteria for Candidate Species for
Fish Culture
(i)It must withstand the climate of the
region in which it will be raised.
Thus, the rearing of coldwater fish
like salmonids and trout is limited to
temperate regions or mountain
areas of tropical countries because
they can not tolerate warm water
with its low oxygen content.

6. (ii) Its rate of growth must be
sufficiently high.
Small species, even if they reproduce well in
ponds and accept formulated diets, are not
the most suitable for rearing.
Also, the best culture species are those which
are low in the food chain, e.g., plankton
feeders, herbivores, and detritivores. Their
culture is also least expensive, even on an
intensive scale, because they do not need
to be given diets which have a high content
of animal protein.

7. (iii) It must be able to reproduce
successfully under culture
conditions.
Species for culture should be able to
reproduce in captivity/confinement
without needing special conditions that
have to be fulfilled, and which give high
returns on eggs and fry.

8. (iv) It must accept and thrive on
abundant and cheap artificial food.
Culture species which feed on cheap
artificial feeds and give low feed
conversion ratios (FCRs), also tend to
give very good production rates, thus
bringing in better financial returns.

9. (v) It must be acceptable to the consumer.
Even if all the foregoing criteria are met by a
candidate species, it is not worth culturing if
there is no market for it. It is possible, though,
to promote acceptability of or encourage
consumption of a particular species to ensure
that it will eventually sell in the market. (This
was the situation with tilapia in the Philippines
prior to the introduction of the bigger-sized,
lighter coloured S. niloticus in the early 1970s.)

10. (vi) It should support a high population
density in ponds.
Social and gregarious species which can grow
well to marketable size even under high density
conditions in ponds or tanks are preferable to
those which can be grown together in dense
numbers only up to a certain age beyond which
they eat each other (e.g., pike).

11. (vii) It must be disease-resistant.
Reared fish must be resistant to disease
and accept handling and transport
without much difficulty.
Tilapia for example is an ideal species for
culture because of its high resistance to
disease even in highly intensive culture
systems.

12. initial and basic requirement
of fish culture:
production of young fish for
stocking

13. Fish culture today is hardly imaginable without
the artificial or semi-artificial mass propagation
of fish seeds of cultured fish species.
The need for production of quality fish seed for
stocking the artificial ponds and natural water
bodies has been steadily increasing.
Artificial propagation methods constitute the
only practicable means of providing enough
quality seed

14. NATURAL PROPAGATION OF FINFISH

15. Significance of Propagation
to survive and flourish and add a large
number of offspring to the population.

16. Biology of Propagation
The propagation habit is the most vital adaptation
of the fish to its environment with respect to
survival.
For successful propagation, the place where eggs
are released should have optimal conditions with
respect to oxygen, temperature, food, etc. and
should be almost free of enemies. Those fishes
unable to find such conditions have gradually
been eliminated.

17. The nature of the propagation habit of
any fish is determined by:
1.the age or time of sexual maturity
2.the season of propagation,
3.the place of propagation, and
4. the extent of parental care

18. Age of sexual maturity
Some fishes, such as Tilapia spp., become
sexually mature within a few months, while
others may take as long as a few years.
Sexual maturity depends on:
a. Climate - Sexual maturity is delayed
in cold climates, while it is accelerated in
warmer environments.
b. Type of spawner – whether multiple
spawners or season-bound spawners

19. Season of propagation
- a slight change in temperature,
oxygen, and other parameters
greatly affect cold-blooded
animals
a. Multiple spawners –matures earlier than
season-bound spawners
b.Season-bound spawners

20. Place of propagation
Freshwater fishes are known to spawn in
three different types of sites:
(1) confined waters
(2) flowing waters
(3) inundated terrains.

21. Parental care
- is a very important adaptation among
fish for ensuring the survival of their
offspring where parent fish look after their
offspring during their most critical stage of
life when they are defenseless and very
sensitive.

22. Types of Parental Care
Passive - This is actually the “hereditary
foresight” of the females to provide more
yolk for the embryo to sustain life for a
long time or to place the eggs on such
sites where the optimum environmental
conditions are met and beyond the reach
of enemies. Some fish have in their eggs
a poisonous substance which keeps
predators away.

23. b. Active
- either one or both of the parents take
an active part in caring for and
defending their eggs, larvae, and
sometimes the fry as well. This includes
the selection and preparation of a
suitable place for depositing the eggs,
selection of a good substrate to which
the eggs can adhere, collection of nest
making materials, and preparation of
the nest

24. Development of the Sexual Products
1. Development of eggs
Stage I: The primitive egg cells
(ovogonium or archovogonium) are
very small, their size being hardly
bigger than that of other cells (8–12
microns). They multiply by normal
mitosis.

25. Stage II: The egg cells grow to a size
of 12–20 microns, and a follicle
begins forming around each egg cell.
The follicle, whose function is to
nurture and protect the developing
egg, eventually becomes a double
layer of cells.

26. Stage III: During this stage, the egg
cell grows significantly larger to
attain a size of 40–200 microns and
becomes enclosed by the follicle.
.

27. These first three stages mark the
period prior to the accumulation of
nutrients in the developing eggs.

28. Stage IV: During this stage the
production and accumulation of the
yolk begins; this is a process known
as vitellogenesis. The egg
continues to grow to a size of 200–
350 microns with the accumulation
of drops of lipoid materials in its
cytoplasm.

29. Stage V: This marks the second
phase of vitellogenesis. The
cytoplasm is now full of lipoid drops
and yolk production begins. The egg
size reaches 350–500 microns.

30. Stage VI: This is the third phase of
vitellogenesis, during which the yolk
plates push the lipoid drops toward the
edge of the cell where two rings begin
forming. The nucleoli, which take part in
protein synthesis and the accumulation
of nutrients are seen adhering to the
membrane of the nucleus. The size of
the egg is now 600–900 microns.

31. Stage VII: The process of
vitellogenesis is completed during
this stage and the egg attains a size
of 900–1 000 microns. When the yolk
accumulation ends, the nucleoli
withdraw into the centre of the
nucleus. The micropyle (a small
opening on the egg shell) develops
during this stage.

32. Stages IV, V, VI, and VII are the
stages of vitellogenesis, when yolk is
synthesized and accumulated in the
egg cell. The egg is now materially
ready. To reach this stage of
development, the female fish needs a
lot of protein in its food and a
favourable temperature range

33. Further development of the eggs
toward ovulation (final ripening) is
regulated by gonadotropin
hormones, which are formed and
stored in the pituitary gland or
hypophysis. Some hormones of the
hypophysis, such as FSH (follicle
stimulating hormone) and LH
(luteinizing hormone), are
continuously produced and secreted

34. On the other hand, the steroid
type of hormones (oestrogens)
secreted by the capsule (theca)
of the follicle “inform” the brain
about the stage of egg
development.

35. On the completion of stage VII, the egg
may remain as such for several months
without any change, and this forms the
“dormant” or “resting” phase.
This resting or dormant phase will
either end in ovulation if favourable
conditions occur, or in follicular
putrefaction and resorption in the
absence of such conditions.

36. When the environment changes for
the better, the fish starts gathering,
through its sense organs, all the
necessary information about
environmental conditions; e.g.,
temperature, suitable place for
spawning, water current, floods,
presence of fish of the opposite sex,
etc.

37. This sensory information accumulates in
the hypothalamus of the brain and when
a certain threshold level is reached the
hypothalamus gives an order through a
hormone (gonadotropin-releasing-
horwone, GRH) to the hypophysis to
release gonadotropins into the blood
system. The gonadotropins, thus
released, reach the gonad and trigger
the preovulation process and final
ovulation.

38. The first effect of gonadotropins on
the egg is the movement of its
nucleus toward the micropyle. This is
followed by what is termed as
“hydration”, wherein the eggs absorb
water. All these are completed during
the preovulation stage.

39. After preovulation, the membrane of
the nucleus disappears, the
chromosomes become visible, and the
first cell division of meiosis occurs
(during which the total number of
chromosomes is reduced to half). At
the same time, the follicle keeping the
egg fixed on to the wall of the ovary
gets dissolved by enzymes and the
“ripe for fertilization” egg falls into the
cavity of the ovary.

40. The second cell division of meiosis
normally takes place in the presence
of the sperm, which intrudes into the
nucleus of the egg through the
micropyle. Therefore, the presence
of the male pronucleus is necessary
for the development of the female
pronucleus.

41. OOGONIAL PROLIFERATION PHASE
VITELLOGENESIS PHASE
RESTING OR DORMANT PHASE
OVULATION RESORPTION/
PUTREFACTION
SPAWNING

42. What happens during ovulation?
1.Migration of the nucleus to the periphery
of the egg near the micropyle
2.Hydration
3. Breaking/rupture of the follicle
4. First phase of meiosis(cell division of
meiosis in which the number of
chromosomes is reduced to one half)

43. 2. Development of Sperm
The process of development of
sperm is far less complicated than
that of eggs.

44. Spermatogonia
propagation by mitosis
Development of primary
spermatocytes and later two
secondary spermatocytes
Production of two
spermatozoa or sperm in
each spermatocyte
Collection of sperm in the
cavities of the tubules of the
testis in a dormant state

45. Characteristics of the Sperm
oThe sperm are motionless in the
testis but become motile when they
come in contact with water.
oThe motile period of the sperm is
very short and depends on the
temperature of the water.

46. oThe sperm of warmwater fishes
move actively by their filamentous tail
for only about half or one minute.
o The fish sperm are very small, their
estimated number in one cubic
centimetre of milt being about 10
000–20 000 million depending on the
denseness of the milt.

47. Fertilization and Fertilized Egg
oThe eggs that have fallen into the
cavity of the ovary do not have definite
shape.
oThe egg shell is soft and tightly
surrounds the cell “kernel”, which
includes the nucleus and the mass of
yolk.

48. oWhen the ripe egg falls into the
water it assumes a round shape and
within a short time begins to swell.
oThe water penetrates between the
shell and kernel of the egg and thus
the perivitelline space develops.

49. oThe micropyle closes within a
minute, after which no sperm can
enter the egg. The swelling usually
lasts for about one-two hours. The
egg then takes its final form and
becomes water-hardened. The
swelling, however, does not alter the
size of the kernel.

50. oThe fertilized fish eggs can be of
different types. However, for practical
purposes, two principal categories
can be distinguished:
1.non-adhesive
2.adhesive

51. Non-adhesive eggs
Types:
1. buoyant eggs - specific weight slightly less
than that of water
2. floating eggs - specific weight weight is slightly
higher than that of water
3. semi-floating eggs- specific weight is higher
than that of water
4. rolling eggs - specific weight is higher than that

52. What determines the specific weight
of eggs?
Answer:
The specific weight of eggs is determined
by the:
a. size of the perivitelline space
b. the specific weight of the kernel-
affected by presence or absence of
oil droplets

53. Adhesive eggs
oThese eggs have an adhesive layer
on their shell, which becomes activated
when the egg comes into contact with
water.
oThe adhesive layer sticks the eggs to
some objects or to each other.

54. oTwo types of attachment can be
distinguished:
1. eggs sticking to objects
2. eggs sticking only to each
other, forming a clump or egg
mass

55. oThe adhesiveness can either be:
1. strong and the eggs suffer damage
if torn off from their substratum
2. quite weak and the eggs can be
easily removed

56. Variations:
1. The adhesiveness gradually
weakens during the course of egg
development.
2. Higher salinity effects a negative
influence on adhesiveness.
3.The fish eggs vary in size

57. The factors which determine the
size of the egg are:
1. the size of the egg “kernel”
2. the thickness of the egg shell
3. size of the perivitelline space.

58. *The first two determine the size of
the “dry” eggs (i.e., before they come
in contact with water), while the third
determines the size of the water-
hardened eggs.

59. Thank you!