Techniques/Methods of Fish Breeding






Fish Farming in pictures
Fish breeding is synonymous to fish propagation which simply means multiplication. Breeding
entails all the various techniques or methods which can be used or at least maintain a fish stock
(i.e. methods of fish seed production).

This concept in fish production is important when an increase demand for fish and for culture is
considered. Also, in tropical world, many fish species breed only once a year. Therefore, a
continuous demand for fish seed makes fish propagation sine-qua-non. There are various
techniques which differ from different parts of the world depending on local conditions and
available local facilities. For instance, in developing world where facilities are not available, fish
seeds are obtained from the wild while in advanced countries where there are facilities,
propagation is completely artificial.
Basically there are 3 types of fish breeding/propagation.

- Natural propagation/breeding techniques
- Naturally induced breeding/pond or enclosure propagation
- Artificial propagation through hypophysation.

1. Natural breeding technique

This is a technique whereby fish are allowed to breed in their natural
environment and their eggs, larvae, fry and fingerling are collected for pond stocking. The fry
and fingerling (fish seeds) of Cichlids, Clarias, Chrysicthys as well as mullets (Mugil sp) are
available in Nigerians waters fairly in large quantities all the year round. Heterotis niloticus is
seasonal in abundance and can be obtained within a short period in a year usually at about the
beginning of the rainy season. Many other species are known to be available during the rains
(April to September) in the flood plains-inundated river banks and the estuaries. However, much
is still desired to be studied in Nigeria concerning the season and nursery grounds of other
species. Accurate statistics of fish seeds obtained from the wild is not available in Nigeria.
The collection of fish seed is carried out with no physical damage to the seeds which entails the
elimination of gill-nets and hooks as used gears. Gears for collection include the hand net; lift
net, drag/seine nets, cash nets. Light is used to attract them at night, pieces of feeds, GNC can
also be used to attract them to avoid mudding during seining. Special traps especially in streams
and river could be used. Before transportation, the collected fry are fingerling are kept in Happa,
net or pots and starve overnight in clean water to avoid defaecation which can utilize O2 during
transit. The collected fry and transported in well aerated, cool water to the pond for stocking.
Problems associated with natural breeding technique include:

- For many species, the seed may not be available as and when needed or required. Hence,
there is shortage of fingerling for stocking leading to low fish production.
- Weed fishes and fish enemies e.g. Dragonfly larvae, water bugs which may feed on eggs
or attack the fry or compete for the fish food may also be collected with the fish seed.
Fish parasites e.g. leeches are collected with fish seed from the wild and introduced inadvertently
into the rearing ponds.
- Difficulty of accurate identification of the fry/fingerling stages of certain species which
results in the desired species being stocked with undesirable stunted species. e.g.
observed in catfish with Barbus.
- There is high mortality during catch/collection and at transportation.
- May be uneconomical e.g. cost of going to the wild, pay workers to gain access to the
spawning sites through trial and error methods.
However, natural breeding technique needs little or no skill which is an advantage.

2. Ponds or enclosure propagation
Essentially it is a naturally induced breeding technique that involves introduction of broodfishes
or brooders into specially constructed ponds or tanks and allow them to breed. It is a common
practice to leave the brooders breeding repeatedly. This is not ideal in terms of quality and is
anti-selective since the age and parentage of the fish cannot be determined after some time.

Therefore, a proper and systematic pond propagation technique that would ensure production of
fry of known age is recommended. Usually, ponds used for propagation are small, about 0.1ha or
100m2 and shallow usually less than 1m. Cement/concrete tanks with measurements of 5x3x1m
have been successfully used for pond propagation of Tilapias in Nigeria. Some fishes which
reproduce easily in ponds are Tilapia, Oreochromis, Sarotherodon, Lates, Heterotis, Clarias,
Carps and Gymnarchus breed in special ponds. Intensive efforts are going on to propagate
Chrysichthys in ponds. For example, the propagation of tilapias in ponds does best in shallow
waters and the pond must have sandy bottom. If tank is used, the floor of tank is usually covered
with a layer of sand for making their nests (spawning area). The eggs hatch within 1-2days after
external fertilization. These hatchlings/larvae are usually carried by one of the two parents until
they are free to go or fend on their own. The fry move in shoals (school) along the edges of the
water from where they can be collected. Discuss the newly designed special receptacle for
propagating tilapias.

In case of Clarias, it requires moving water and hence an artificial water current of
the water must be created. Carp requires a special pond called Hoffer or Dubisch pond and it
must have a large bottom with grasses and it is shallow. Temperature and dissolved Oxygen are
crucially and optimally required in the ponds. In addition, the water must be free of other fishes
especially the carnivorous ones e.g. Hemichromis. Also, mention the success story so far about
Chrysichthys breeding in an enclosure.

The above techniques are simple and inexpensive in addition to achieving the best possible
survival rate, good growth and health for the fish. The techniques require no sophisticated
installations or tools and without difficulties and risks involved in artificial fertilization.

3. Artificial Propagation through Hypophysation
The hypophysation technique which uses the pituitary gland (the hypophysis) to induce
spawning in fish can be carried out at any time of the year and under any environmental
conditions. The technique ensures fish seed availability at all times of the year. For instance,
using this technique a single common carp (Cyprinus carpio) has been induced to spawn five
times within a year at intervals of 60,62,41 and 186 days between successive spawning, even
though carp breeds naturally only once a year.

Artificial propagation was first described in 1765, but was neglected until 1842 when it was
described again. A number of experiments were carried out and by 1937 artificial propagation at
commercial level was attained. By 1964, it has spread to many parts of Europe, America, Japan,
China, Israel but to date there are increased trials in Nigeria with varying degrees of success. It
was first reported in Panyan fish farm and Agodi fish farm where carp propagation was
successful. Other privately owned fish farms have tried hypophysation using catfishes e.g.
Clarias gariepinus, Heterobranchus bidaorsalis.
For the purpose of easy description and discussion, artificial propagation can be divided into 6
stages as:

- Selection of brooders
- Maturation of the brooders
- Stripping i.e. obtaining eggs and sperms (milt) from the brooders
- Fertilization
- Incubation of fertilized eggs to ensure that they hatch
- Rearing of the larvae/fry up to fingerling stage.

On the whole, more fry can be obtained from an individual fish through artificial propagation
involving stripping after hypophysation when compared to what is obtained through other
propagation techniques.

ADVANTAGES
- Fish seed is guaranteed all the year round
- Fish seed is obtained outside the natural environment of fish.
- It increases the survival rate of the fry
- It improves quality by crossing two different species (i.e. hybridization) can be obtained.

DISADVANTAGES
- The donor fish has to be sacrificed in most cases and hence of loss of fish.
- The whole process is laborious and highly technical.
- Very expensive in that it requires proper housing, constructions of tanks, installation of
jars in a close circulatory system.

It should be noted that artificial (i.e naturally induced or through hypophysation) production of
fish seed are carried out in enclosures known as Hatcheries which may be an indoor or outdoor
facilities and they require inputs such as brood stock, adequate water supply and suitable feed.

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