International Journal of Aquaculture, 2016, Vol.6, No.7, 1
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The fish was fed 5 times every day, between 8 am and 4 pm, at 2 hour intervals, following recommendations by
Nagoli and Balasubramaniam (2008) and Hecht (2013). During the first week of the experiment, fry in treatment 1
was fed on an egg yolk diet with plankton supplements while fry in treatment 2 and 3 was fed on a diet of soy
milk prepared from unroasted and roasted beans respectively, and plankton supplements. Fry fed on egg yolk diet
was fed till satiation while soy milk was applied in respective tanks at an application rate of 1 ml/liter of water
each day. Thus, 500 ml of soy milk was applied in each tank each day.
From the second week of the experiments, fish meal was included in the diets of fry in all treatments. As with the
soymeal used in preparing soymilk, the fish meal was double sieved to remove hard residues that were likely to
have come from scales and other hard parts of the fish. The fish meal was mixed with water before feeding the fry.
The fish meal, fed till satiation, was given to the fry twice each day, at 10 am and 2 pm.
3.4 Data Collection and Analysis
Data on growth, expressed as weight gains of fry, was collected bi-weekly over a period of 6 weeks (42 days) by
sampling 50 fry from each tank and recording the weight on an electronic balance each time sampling was done.
Survival of experimental fish in each tank was recorded at the end of the experiment by physically counting the
number of fry alive. A thumb counter was used to assist the counting process.
Growth rate in each treatment was measured as specific growth rate and average daily weight gain (ADWG).
Specific growth rate, average daily weight gain and survival rate was calculated using the following formulae
(Pillay, 1990);
i. Average Daily Growth (ADG)
ii. Specific Growth Rate (SGR percentage)
Where, W
2
= Final weight in grams
W
1
= Initial weight in grams
D = time interval (number of experimental days)
iii. Body weight gain (BWG)
Where, W
1
= initial mean weight, W
2
= final mean weight
3.5 Water Quality Monitoring and Management
Ammonia level in rearing units was checked bi-weekly using the Phenate method. Temperature, pH and Dissolved
oxygen (DO) of water in each tank was recorded twice every day, at 8 am and 2 pm, using a digital water checker.
To maintain good water quality in the rearing tanks, partial water replacement was done by flashing out 10 cm in
each tank at the end of each day. Waste feed and faecal matter remaining at the bottom of the tanks was siphoned
out after every 3 days. Lost water after siphoning out waste material was replaced. Aeration stones were used to
supply oxygen.
Data analysis was done using SPSS (Statistical Package for Social Scientists) Version 20. One-way Analysis of
Variance (ANOVA) was used to test for significant differences among treatment means. Tukey HSD test was used
to separate means after ANOVA showed significant difference among treatment means.
