FISH SEED PRODUCTION
CHAPTER
THIRTEEN
FISH SEED
PRODUCTION
BROOD STOCK
SELECTION
Brood
stock means a group of sexually mature individuals of a culture species that is
kept separate for breeding purpose.
13.1 DIFFERENCES
BETWEEN MALE AND FEMALE SEXUALLY
MATURED FISHES
Male
and female breeders may be easily differentiated by the shape of the body and
the relative position of 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.
External signs of the brood stock
A male brood stock will release milt under a slight
abdominal pressure: Its belly is not blown up but rather slim; it sometimes has
callosities on the head.
A female brood stock has a well-rounded and soft or semi-soft belly, its genital papilla is
erect and reddish, its anal opening is
enlarged and protruding.
QUALITIES OF
GOOD BREEDERS
1. Active or hardy( must be in good health)
2. Have a mature gametes.
3. Fairly big size.
WAYS OF HANDLING FISH
BROOD STOCK
1. Ensure careful handling of the breeders to avoid
stress.
2. Allow a shorter period of time( 48 hours to one
week) in a breeding compartment.
3. Develop a secure holding technique that minimized
the effect of struggling.
4. Cover the fish’s eye with a wet cloth whenever
possible.
5. Minimize noise during all handling many fish have
a very acute sense of hearing.
6. Ensure transportation takes place in the morning
or late in the evening.
13.2 BREEDING
OPERATION
Several methods exist for the breeding or propagation
of cultivated fish. These methods of fish breeding can Be grouped into the
three categories
1.
Natural breeding
2.
Semi-natural breeding
3.
Artificial breeding
1.
NATURAL BREEDING:- Males and
females are placed together in a breeding area such as small pond or any
enclosure where they spawn naturally. This method is usually used for example
to produce tilapias cheaply. The
successful breeding of certain species may require some environment
manipulation such as the inflow of new water and a sudden rise of the pond
water level for the African catfish clarias, the presence of grassy vegetation
as egg collection nest for common carp etc
NATURAL
BREEDING THROUGH ENVIRONMENTAL INDUCEMENT
One of the best
ways to induce fish is to spawn, especially difficult- to- spawn species to
stimulate the natural conditions. Among factors that encourage fish to spawn
are the environment, the food and the rainy season. ENVIRONMENT: the right water conditions are among the most
basic requirements in spawning fish. The water conditions should be similar to
those in the natural environment of the species. Also another important
environment conditions the right tank set-up including hiding places, spawning
sites, lighting, and water current and social conditions.
FOOD: - The right foods are important to encouraging spawning.
Without proper foods natural condition cannot be entirely recreated. Some of
the live foods that can make a different in spawning success are mosquito
larvae fruit flies shrimps &flying insects.
STIMULATING THE RAINY SEASON:
- Many fish species spawn during the rainy season in natures. By stimulating
the rainy season in aquaria difficult to –spawn species can be induced to
spawn. Rains affect the water chemistry, the water high, and the water
temperature. In order to stimulate rainy conditions the tank level should be
reduced to half its normal height. Each day add 5% of the tank volume. The
water added should be very soft and slightly cooler than the tank temperature.
To stimulate the rain, used a drip system or spray bar for several hours a day
and stimulate storms by flashing light in a dark room. Thunder can be created
by playing a recording of a storm, recording of rattling thin metal cake pans. The
process can be repeated until fish shown sign of spawning preparation.
TILAPIA BREEDING: - In all tilapia (oreochromus species) the
male excavates a nest in the pond bottom (generally in water shallow than
3feet) and mates with several females. After a short mating ritual females
spawns in the nest (about two to four eggs per grain of brood female), the male
fertilizes the eggs and she then holds and incubates the eggs in her mouth
(buccal cavity) until they hatch. Fry remain the female mouth through yolk sac
absorption and often seek refuge in her mouth for several days after they begin
to feed. Sexual maturity in tilapia is a function of age, size and
environmental conditions. Tilapia population in large lakes Matures at later
age and larger size than the same species raised in small farm ponds.
SEMI-NATURAL PROPAGATION/
BREEDING:-The
Fish (usually the females only) are first given one injection of chemicals such
as a pituitary gland extract, which will trigger spawning. Males and females
are then placed together in a specially prepared breeding area such as a small
grassy pond or an enclosures where spawning takes place. The fertilized eggs
are usually collected and reared under improved condition either natural or
artificial
ARTIFICIAL BREEDING:- This is a method of breeding
in which the sexually matured fish are manipulate to spawn or reproduce.
The females are
given one or more injection of chemicals which regulate the final ripening of
dormant egg in the ovaries. As soon as the eggs are ripe, they are stripped
from the females. The males are usually also injected. Egg are artificially
fertilized with sperm obtained from the males and reared under controlled
condition the technique ensure fish seed availability at all times of the year.
In Nigeria, it was first reported in panyan fish farm and
Agodi fish farm where propagation carp was successful. Other privately owned
fish farmers have tried hypophysation using catfish.
13.3 STEPS INVOLVED IN ARTIFICIAL BREEDING OF FISH.
1.
Selection
of brood stock
2. Conditioning of brood
stock
3. Inducement of brood stock
4. Stripping of female brood stock i.e to obtain eggs.
5. Extraction of milt from male brood stock
6. Fertilization of eggs
7. Incubation of fertilized eggs to ensure that they hatch in
aquarium or hatchery tank.
8. Management of fish hatchling.
9. Nursery of fry.
10. Feeding of fry after yolk absorption.
BASIC REQUIREMENTS FOR ARTIFICIAL PROPAGATION OF FISH(BREEDING
MATERIALS)
The requirements are mature brood stock, weighing scale,
thermometer, Acetone(for preservation of pitutuary gland), mortal and pestle,
calibrated jar, dissecting kit, microscope, syringe and needle, aquarium tank/
hatching trough, Knife, hand basin, clean water, plastic spoon, bowl, kakaban,
saline solution.
13.4 DESCRIPTION OF
THE ARTIFICIAL PROCESS OF OBTAINING FINGERLINGS
The brood stock( both mature male and female fish) are
injected with hormones to aid eggs and milt maturation, ovulation takes place
10-12 hours after injection. The female brood stock abdomen was gently pressed
to release the eggs( stripping) into a dry bowl.
The male brood stock was sacrificed to obtain the testes, after
which the milt was obtained by squeezing its abdomen. The eggs and milt are
mixed together with plastic spoon or feather to effect fertilization. Water or
saline solution was added, the eggs are then incubated and hatched in a
flow-through trough or on a kakaban or netting materials. The hatchling will
start swimming out after 2-3 days depending temperature. The hatchlings are
removed from the unhatched eggs. Feeding of hatchling commences immediately
yolk sacs are absorbed. The hatchlings develop into fry which develop into
fingerlings.
13.5 THE NURSING
PROCESSES OF FISH FEED
1. Aeration – This is done by
using the following methods: Padding, splashing, sprinkle.
2. Feeding with natural food
organisms( plankton) after four days.
3. Introduction of artificial
feeds (powdered feeds after one week)
13.6 MANAGEMENT
PRACTICE IN FISH FEED PRODUCTION
1. Separating dead or
unfertilized eggs from the hatchlings.
2. Monitoring water quality
especially the dissolved oxygen(DO), Temperature.
3. Transferring outdoors to
nursery tanks or pond after 21 days.
4. Sorting the shooters or
jumpers from the stunts.
5. Rear or raise the jumpers
separate from the stunts.
The artificial
production of fish naturally induced or through hypophysation production of
fish seed are carried out in enclosures known
as HATCHERIES, which may be an indoor or outdoor facility and
they require inputs such as broodstock, adequate water supply and suitable
feed.
ARTIFICIAL BREEDING OF CATFISH
a.
SELECTION OF BROOD STOCK: Mature
parents of catfish (claries or heterobranchus spp) weighing between 500and 1000
grams can be obtained from the wild or from breeding stations. Mature females
show soft and swollen bellies and ripe eggs can be squeezed out of the genital
papilla. Mature males have well developed genital papillae. The parent should
be kept in suitable tanks or pond and fed well.
b.
COLLECTION PREPARATION AND INJECTION OF
PITUITARY HORMONES:- The pituitary hormones is obtained from
pituitary gland located on the ventral side of the brain. The male catfish is
sacrificed and the pituitary gland is removed it is squashed in a mortar, mixed
with 5ml physiological saline solution and drawn into a syringe. This
preparation is injected into the back muscle of the female. In place of
pituitary extract a synthetic hormone like ovaprim can be used. The injection
female is placed in water in a tank or a pond and not disturbed till it is
ready to be stripped. This may take between 12 and 36 hours depending on the
water temperature.
c.
COLLECTION OF MILT (SPERM): The
testes are removed from the sacrificed male catfish. The milt (sperm) is
squeezed into about 5ml of physiological saline solution. This is stored in a
refrigerator till needed for fertilizing the eggs.
d.
STRIPPING OF EGGS: It takes
between 7 and 21 hours after injection before the egg can be stripped. Within a
temperature range of 200C-300C. This is known as latency
period. The higher the temperature within this range the shorter the
latency period. Stripping is done by gently pressing the abdomen of the fish
from the pectoral fin toward the genital papilla. The eggs will flow out and
should be collected into a dry plastic bowl. About 500-700 eggs can be found in
1gram of egg mass, the eggs should be prevented from coming into contact with
water.
e.
FERTILZATION OF EGGS: The stored
milt is poured onto the eggs and clean water is added after about 30 seconds.
The mixture is gently and continuously stirred with a soft object such as a
feather.
f.
INCUBATION OF EGGS: The
fertilized eggs are spread at the bottom of an incubation (hatching) tank such
as a concrete or plastic tank containing water, or in a kakaban place in a
pond. The eggs can be placed on a 1mm mesh screen in the water. It takes 20-57
hours for the eggs to hatch at the water temperature range of 200C-300C.
The higher the temperature within this ranges the shorter the incubation
period. It is necessary during incubation to ensure a good supply of oxygen.
This can be achieved by aerating the water or by ensuring a continuous flow of
water through the system. During the incubation period it is important that the
eggs be protected from bright light, to prevent the destruction of the eggs.
Dead eggs soon turn whitish eggs, and the degree of survival of eggs can be
determined by the percentage of whitish eggs. The fewer the whitish eggs, the
higher the survival. At the end of the incubation period the larvae wriggle out
of the eggs and congregate in the dark comers of the hatchery tank.
g.
NURSING OF LARVAE: Since the
larvae are still attached to their yolk sac, they do not feed for two or three
days. The larvae are transferred into well prepared nursery ponds or tanks
which must have good quality water and free from predators. There must be
adequate natural food in the nursery particularly zooplankton, which can be
achieved by maturing/ fertilization. Larvae develop into fry, which should be
transferred into earthen ponds to be nursed until they grow into fingerlings.
ARTIFICIAL METHOD OF TILAPIA
Healthy sexually active brood fish are
important prerequisite for successful stripping of gametes.
a.
MALE: The quantity and quality of milt
varies between males the greater their social dominance the greater and
therefore the ease of stripping. To strip a male the abdomen is squeezed gently
from the pectoral area toward the genital region. This procedure also empties
the bladder of urine and care should be taken not to mix it with the milt. It
is often more difficult to obtain milt from tilapia species than from mouth
brooders. If sufficiently milt is not available males can be sacrificed and
their testes removal and macerated on dry side prior to fertilization the macerated testes should be mixed with
about 0.5ml of water or 0.9% saline solution
and then add to the eggs to ensure sperm activities sperm from at least three
males should be pooled and used.
b.
FEMALES: A female can only be
successfully stripped if all her eggs have been ovulated into her ovarian
cavity when the eggs have been ovulated, the ovipositor descends and is almost
perpendicular to the body. The genital papilla generally becomes swollen and
pinkish in colour. Often the body colouration deepens and females become more aggressive. Female showing these
external characteristics are ready for manual stripping.
c.
PROCEDURES FOR STRIPPING AND FERTILIZATION OF
EGGS: Females should be caught gently in a deep net and wrapped in a
damp paper towel or cloth to reduce skin damage and drying. If large brood fish
are used they may be sedated to facilitate handling. If anaesthetics are used
the anaesthetized fish should be rinsed in freshwater before stripping to avoid
the drug contaminating the eggs. The eggs are then fertilized with milt from
the desired males(s).
The ovarian
fluid is and excellent sperm activator. Therefore provide sufficient milt is
available undiluted milt should be added directly to the eggs stirred gently
and left for 3-5 minutes. The fertilized egg are than washed with clean, warm
water and transferred into incubations.
INCUBATION OF TILAPIA EGGS: The
method required to rear tilapia eggs varies between species. In mouth brooders
the most important requirement is that eggs should be kept in gentle motion,
whereas tilapia eggs develop in static conditions. All eggs should be reared in
well aerated, clean water of high quality.
13.7 BREEDING
SYSTEM
The commonly used breeding
systems are described below:
1.
ZUG-JAR (CONICAL OR FUNNEL UP- WELLING JARS): The
zug-jar can be made from glass, plastic, Perspex, fiberglass, metal or linen.
These types of containers are the most available and therefore used in most
hatcheries. In these incubators water flow in from the bottom of the container,
the flow can be adjusted to suspend the egg or fry mass in continuous motion in
the water column.
2.
ROUND-BOTTOMED (DOWN-WELLING CONTAINERS): These
containers were originally called MacDonald jars and were made of glass. They
are cylindrical in shape with a round bottom. Water enters the container from a
fixed pipe from above. The flow can be adjusted to gently rotate the eggs.
3.
KAKABAN(SPAWNING NET):
Kakaban is a netting materials placed on
top of the water in bowel. On the kakaban, the fertilized eggs were spread
homogenously in a single layer for the hatching of the eggs.
ADVANTAGES OF ARTIFICIAL BREEDING
1.
Fish
seed is available all the year round.
2.
Fish
seed is obtained outside the natural environment of fish.
3.
It
increases the survival rate of the fry.
4.
To
obtain high quality hybrid: It is achieve by crossing two different species
(i.e hybridization) can be obtained.
5.
To
make fingerlings readily available.
DISADVANTAGES OF ARTIFICIAL BREEDING
1.
The donor fish usually sacrificed which lead to loss
of fish.
2.
The whole process is laborious and highly technical.
3.
It is too expensive i.e it requires proper housing,
construction of tanks, installation of jars in a close circulatory system.
STRUCTURE QUESTIONS
1.
Which of the following fish species exhibit parental care (a)
carp (b) Electric fish (c) lung fish (d) Niger perch (e) Tilapia
2.
Which of the following is not a breeding process in fish? (a)
courtship (b) feeding (c)
fertilization (d) hatching (e) spawning
3.
The ability to spawn hatch and raise fish to adulthood in a
laboratory setting is known as (a) an
ocean-based aquaculture system (b) genetic engineering
(c) Aquapod aquaculture (d) a recirculating aquaculture system.
4.
Managing fish populations by maintaining them at a maximum
growth rate and achieving maximum yield
while keeping fish available for the future
is best called? (a) maximum sustain able
yield (b)non target species
sustainable by catch (c) sustainable fisheries management (d) system fisheries management
5.
Which of the following is not among a factors that encourage
fish to spawn is (a) food (b) rainy
season (c) environment (d) pounding
6.
Thunder can be created in a pond by ? (a) playing record of
storm (b) playing a recording of
rattling (c) a recording of music with bass (d) all of the above
7.
Artificial breeding involves the following stages except? (a)
selection of brooders (b)
maturation of the brooder (c) stimulating rainy season (d) stripping
8.
The pituitary hormones is obtained on the ventral sides of
the? (a) stomach (b) brain (c)
chest (d) bowel
9.
The following are common breeding system except? (a)
incubation tray (b) kakaban
(c) zug-jar (d) strippers
10.
The production of fish seed are carried out in enclosures
known as? (a) Hatchery (b)
stripping (c) inducement (d) brooders.
11.
A sexual mature female fish should? (a) have plenty of eggs
(b) be ready to spawn (c) have
a fat abdomen (d) have a reddish genital papilla.
12.
Artificial breeding of fish is important in order to (a)
Reduce wild fish population (b)
Increase brood stock population (c) Reduce the population
of fingerlings (d) Obtain large quantities of fish seed.
13.
Which of the following features could be seen in a mature
female fish? (a) Flat
abdomen with large egg sacs (b) Small body size
with flat abdomen (c) Large and distended abdomen (d) Large body size
with flat abdomen.
14.
Stripping of fish is achieved by (a) Fertilizing eggs with milt (b) Artificially mating male and female fish (c)
Gently pressing the genitals to
release milt (d) Gently pressing the abdomen to release eggs.
15.
A sexually matured male or female fish used for breeding is
called (a) Brood stock (b) Fry (c)
Fingerlings (d) Juveniles.
16.
Sorting of fish is done in the hatchery to prevent (a) Insect
attack (b) Disease outbreak (c) Fish
cannibalism (d) Entry predator.
17.
A house for the production of fish seed is called (a)
harvesting (b) hatchery (c)
hatching (d) hatchling.
18.
Stripping in fish is the extraction of (a) blood (b) bone (c)
egg (d) faeces.
THEORY
1. List
five breeding materials ( items used in breeding) of fish.
__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
2. State four qualities of a good brood stock.
_______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
3. State two differences sexually mature male and female
catfish.
_______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
_________________________________________________________________________________________________________________________________________________________________________________
4. Specimen A is HANDGLOVES and specimen B
is KNIFE.
(a) State five activities that require the use of both
specimen A and B in fish processing and preservation.
______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
(b) State three precautions
that should be taken when using specimen B
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
(c) Mention two ways of maintaining specimen
B.
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
5. Specimen C is PLASTIC BASIN and specimen D
is SYRINGE.
(a) Enumerate two functions of specimen C and D in a fish
farm
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
______________________________________________________________________________________________________________________
(b) State two precautionary measures to be taken when using
specimen D in fish hatchery.
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
6. Specimen
E is FINGERLINGS, specimen F is ADULT FEMALE FISH and specimen G
is ADULT MALE FISH.
(a) State one feature each of specimen F and G.
_______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
(b) Describe
the artificial process of obtaining specimen E from specimen F and G.
_______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
7. Mention five management practices in fish seed
production.
_______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
8. How important is the artificial breeding of fish.
_______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
FISHERIES AGENCIES IN
NIGERIA
1.
AFISUN: Association of fish supplier of Nigeria.
2.
FDP: Federal department of fisheries.
3.
SDP: State department of fisheries.
4.
MIOMR: Nigeria institutes for oceanography and
marine research.
5.
NIFFR: National institute for fresh water
fisheries research.
6.
ARFAN: Artisan fishermen association of Nigeria.
7.
NISA: Nigeria ship owner association.
8.
NUFAS: National union of sea foods dealers.
9.
CAFAN: Catfish farmer association f Nigeria.
10.
FISON: Fisheries society of Nigeria.
11.
TADAN: Tilapia Aquaculture Developers Association
Nigeria.
12. NITOA: Nigeria trawler owner Association.
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