FISH FARMING BUSINESS IN NIGERIA

Semi natural or hormone
induced reproduction in ponds/
tanks as describe above has not
proved to be a reliable method
for mass production needed for
large fish farms or distribution centres of catfish fingerlings.
Therefore artificial propagation
under more controlled
condition, stripping of the eggs,
collection of the sperm followed
by fertilization of the eggs has been developed. The artificial reproduction of the
African catfish, as for all fin-
fishes, is a chain of activities
which is more or less similar to
that of natural reproduction. It
starts with the selection of broodstock from nature or from
the broodstock ponds after
which they are transferred to
the holding tank in the
hatchery. Ideal broodfish weighs
between 300–800 grams, Larger fish are difficult to handle,
resulting in a substantial losses
of eggs prior to stripping.
Mature broodfish are selected
according to the following
criteria; • A well distended, swollen
abdomen from which ripe eggs
can be obtained by slightly
pressing the abdomen toward
the genital papilla. Ripe eggs are
uniform in size and a experienced hatchery operator
can see the nucleus as a small
dark point in the centre of the
egg. • A swollen, sometimes reddish
or rose coloured genital papilla.
Note: From a practical point of
view can be stated that all
females are “ripe” once some
eggs can be pressed out and if the eggs are more or less
uniform in size (just put some of
the eggs on the nail of your
thumb andadd a few drops of
water and look). The most common technique to
induce final maturation and
ovulation in the African catfish is
to inject the female with
hormones or pituitary gland
material. The required quantity of
powdered acetone dried
pituitary material or the
number of whole pituitaries are
pulverised in a porcelain
mortar. Then, the required quantity of 1 ml per fish of
physiological salt solution (9
gram of common salt in 1 litre
of water) is added. A syringe is
filled with the suspension and
the injection can be given. The most common method to
administer the hormone
solution, is a injection
intramuscular into the dorsal
muscle.
Note: fill the syringe, put the needle on it and empty the
syringe again into the mortar,
when this is possible you can
start to inject the fish. This
procedure has to be followed as
often the needle gets blocked by pituitary material which is not
completely crushed and it is
unpleasant for the fish and
annoying for the operator to
resolve this problem once the
needle is stuck into the fish. The process of final maturation
and ovulation of the eggs will
start after the administration of
the hormonal material. The
speed of the process is
dependent on the water temperature, the higher the
temperature the quicker the
eggs ovulate. Stripping of the female
spawners is done by gently
pressing their abdomen with a
thumb from the pectoral fin
towards the genital papilla.
Ovulated eggs will flow out easily in a thick yet from the
genital vent if the females
responded well to the hormonal
treatment. The ovulated eggs
are more or less transparent,
flattened and a gram of egg contains approximately 6003
eggs. Under normal condition a
“ripe” female a quantity of
eggs which equals to 15–20 % of
her own body weight. If the fish
is stripped to early the eggs are coming out difficulty and they
have a “flushy” if they are
stripped to late. It is recommended that you
determine the number of eggs
per gramme of the broodstock
used at the station.
Note: The temperatures at the
several stations is rather fluctuating, with higher
temperatures at day time. It
looks like it that the eggs are
stripped to early which results
in very low hatching
percentages (5–10%). It is always much safer to strip the
egg to late then to early
because if you are to early you
will lose all your eggs, if you are
to late you will loose some eggs. The males of the African catfish
cannot be stripped and
consequently the sperm can
only be obtained by sacrificing a
male.The male is killed and
thoroughly dried after which the testis is dissected and placed
in a glass and cut quickly into
small pieces with a scissor and
finally the milt is pressed out
with a pestle or a teaspoon. The
sperm and pieces of testis material is added to the stripped
eggs. The eggs are fertilized by
adding about the same volume
of clean water. The water and
egg mass are mixed by gently
shaking of the bowl. Note: Stirring of the egg must be
continued until the eggs are
placed in the hatching tanks as
the eggs become sticky and
without stirring the will stick
together in one clump. After about 60 seconds fertilization
has taken place and the sperm
has lost its activity and the
fertilized egg are ready for in
tanks or happa's. With this method it is not
necessary to preserve or dilute
the sperm in a physiological salt
solution. Once large number of
females are needed to be
stripped at one morning (5 or more) it is an advantage to take
the sperm first and preserve it
in a 0.9 saline solution.
Note: First a female is stripped
and then the milt of the male is
taken. One drop of water in the bottle with sperm will destroy
the sperm completely while one
drop of water in the bowl of
eggs will only destroy some
eggs.
call 08032861326

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