provided by Research Papers in Economics
Comparative Study of Hatching Rates of
African Catfish (Clarias gariepinus Burchell 1822)
Eggs on Different Substrates
S.K. Macharia, C.C. Ngugi and J. Rasowo
Abstract
The hatching rates of African catfish (Clarias gariepinus) eggs on four natural substrates: the roots of Nile
cabbage (Pistia stratiotes), water hyacinth (Eichhornia crassipes), pond weed (Ceratophyllum dermasum)
and green grass leaves (Commelina sp.), and four artificial substrates: sisal mats, nylon mats, papyrus mats
and kakaban mats, was assessed. Concrete slabs were used as control. The natural substrates performed
better than the artificial ones. Pistia roots gave the best mean hatching rate of 66.2 ± 3.62%. Green
grass leaves were second with a mean rate of 54.0 ± 3.46%, water hyacinth was third with 49.7 ± 3.16%
and Ceratophyllum fourth with a mean of 13.0 ± 2.37%. Concrete slabs gave a mean rate of 18.6 ± 2.8%,
sisal mats 18.6 ± 2.0%, papyrus 12.2 ± 1.2% and kakaban 11.8 ± 1.9%. Nylon mats were the last, with a
mean rate of 4.0 ± 0.7%. The best performing natural substrates were those with the ability to float and
thin fibrous roots that seemed to allow higher aeration ofthe eggs during incubation. The cost of using
natural substrates was minimal.
Introduction
Clarias gariepinus, currently synonymous
with C. mossambicus, C. lazeras and
C. senegalensis, is endemic to Africa and
ranges from Natal and the Orange River
in South Africa through Central, West,
East and North Africa where it is under
culture (Teugels 1986). The widespread
distribution is a reflection of their ability
to tolerate a wide range of environmental
parameters. Clarias species have rapid
growth, a high reproductive potential
and sturdy resistance to environmental
variations (Clay 1977; Hetch et al. 1988;
Hogendoorn 1980). C. gariepinus spawn
naturally in floodplains during the rainy
season, and spawning is induced by rise in
water levels (Pillay 1990). However, seed
collection from the wild is unreliable and
limited to the rainy season.
Demand for C. gariepinus fingerlings in
Kenya, both for aquaculture and as bait,
has increased substantially in the last few
years. The Fisheries Department estimates
that the demand for C. gariepinus finger-
lings for aquaculture activities is 10 million
per year, while the demand for use as bait
in the Lake Victoria capture fisheries is
about 18 million fingerlings per year.
(Government of Kenya Fisheries Depart-
ment 1998). The government supplies
about 5 million catfish fingerlings per year
through the fish farms of the Fisheries
Department and the Lake Basin Develop-
ment Authority (LBDA). There is over-
reliance on the government as the producer
and supplier of fish seed as there are no
established private fingerling producers.
The culture of C. gariepinus in Kenya is
still low in volume as indicated by the
production data (Government of Kenya
Fisheries Department 1998). In 2001,
total aquaculture production was 1 000 t
and C. gariepinus contributed only 2 %
of this (Government of Kenya Fisheries
Department 2002). In contrast, tilapia
production accounted for 48% of
aquaculture production over the same
period (Maitha et al. 2002; Owiti 2002).
There is an urgent need to increase the
supply of seed through the development
of simple and efficient seed production
and management protocols that are easy
to adopt by small-scale fish farmers
themselves. The aim of this experiment
was to test several simple, readily available
and low-cost substrates for hatching
C. gariepinus eggs.
Materials and Methods
The study was carried out at Kibos Fish
Farm of the Lake Basin Development
Authority in Kisumu District, Nyanza
Province, Kenya. At the start of the
experiment, mature broodstock were
seined from the broodstock pond and
transferred to concrete hatching tanks.
The ripe males and females were selected
and their weights measured and recorded.
They were acclimatized to the hatching
tanks for one day without feeding. To
induce spawning, the selected females
were injected with pituitary suspensions
obtained from sacrificed male or female
fish of similar size. After 12 hours, the
eggs were stripped into a dry bowl and
fertilized with milt obtained from the ripe
males. One male was used to fertilize
eggs from three females. The fertilized
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