International Journal of Aquaculture, 2013, Vol.3, No.6, 23
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http://ija.sophiapublisher.com
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including release of inorganic carbon and improving
sediment. Phosphorus mobility, may be obtained
without subjecting fish to dangerously low DO
concentrations by adding manure to ponds about a
week prior to stocking (Jha et al., 2008).
Results of chicken manure in the study clearly
indicate that chicken manure is neither a preferred
sources of particulate organic matter for
O.niloticus
or in non-integrated systems an economically wise
choice of fertilizer to provide N and P for production
of natural foods. This is very useful to the farmer in
that adding manure to ponds can degrade water
quality, fill in ponds, and be labour intensive.
Factors which can limit primary productivity include
low inorganic carbon availability, reduced light
penetration from inorganic turbidity (e.g. wind
mixing or bioturbidation in shallow ponds), water
coloration from dissolved organic matter, or algal
self-shading, and relatively low soluble nitrogen and
phosphorous inputs (Rahman 1992; Francis et al., 2001;
Froese, 2006). The most common is over enrichment
(
excessive feeding or inflow of nutrients) of ponds,
which causes heavy phytoplankton blooms resulting
in high respiration or consumption of oxygen.
From the results of the present study and those of
previous studies (Veverica et al., 1998), it is apparent
that the performance of the diets can be ordered as
follows the control with the least performance followed
by maize bran and chicken manure with moderate
performance and the present formulated diets with the
highest performance among all the diets that have been
studied at Sagana fish farm.
3
Conclusion and Recommendation
This study provides evidence that supports the use of
locally available waste products and feed materials
in
O. niloticus
production and has immediate
usefulness in the profitability of
O. niloticus
culture
locally as cereal bran such as maize bran is generally
cheap and chicken manure are readily available in
Zimbabwe. However, further studies should be undertaken
on how chicken manure should be applied with
proper feeding regimes and ratio to stimulate algae
production, as well as to prevent mortalities in cage
aquaculture.
4
Materials and Methods
4.1
Source of Fingerlings
The fingerlings were obtained from Lake Chivero
located 37 km away from Harare (17°54' South to
30
°47' East). The lake is found in agro-ecological region
2
with temperatures ranging between 13.1
℃
and 26.3
℃
i
n winter and summer respectively (Moyo, 1997). The
lake is hyper eutrophic due to discharge of treated and
untreated sewage effused. The
O. niloticus
was first
introduced in Tiger Bay of Lake Chivero as an exotic
culture species. In 1997,
O. niloticus
first appeared in
commercial catches in the lake and to date it is the most
dominant species caught by the commercial co-operatives.
4.2
Experimental design
Three spherical concrete ponds with a surface area
of 5 566 m² each were identified. Pond one was
applied with chicken manure, the second pond maize
bran was applied and pond three was left to be the
control pond and also as a bench mark pond. A
complete randomized experimental design was used.
The experimental ponds were completely drained
and lime was applied to correct pH to 6.5. The ponds
were filled with water pumped direct from the lake a
week before stocking. The fingerlings were collected
on the 20
th
of September 2011 at 11:40 am from the
National Parks Fisheries Research Station bay using
a seine net. Fingerlings were transported from the
bay in two twenty litter buckets filled with water
mixed with malachite green to prevent the fish from
any diseases before being stocked
.
O. niloticus
fingerlings of a mixed sex were used for the study.
Initial body weight of each fish was (0.15±0.05) g.
Stocking density was thirty fingerlings per pond,
with a mixed sex ratio. The fish were acclimatised to
the experimental environment for 2 days prior to the
start of the experiment. Water was replaced occasionally
and addition of water in the three ponds was done
periodically to compensate the evaporated water.
Composition of dry feed maize bran was given two
times a day (early morning at 8 am and late
afternoon 4 pm). Feeding started a day after the fish
were stocked. Feeding for maize bran pond was
adjusted every two weeks based on the mean weight
of fish. Feed was offered to the fish only at 5% of
the body weight for the feed treatment. The chicken
manure pond was fed with 4 kg of chicken manure
tied in a sack bag which stayed in the water for five
days and removed depending on the change of
colour and development of algae bloom of the water.
4.3
Sampling
After every two weeks, ten fish specimens were
randomly captured from each treatment using a small