International Journal of Aquaculture, 2015, Vol.5, No.24 1
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5
2
small-holder aquaculture in Malawi is the precocious
breeding of this species and the resultant fish
density-driven stunting, compounded by lack of capacity
to control fingerling numbers in the ponds (Chirwa,
2009; Russell et al., 2008). Various efforts have been
made to determine appropriate stocking densities to
overcome this limitation with considerably varied
stocking density recommendations (Russell et al.,
2008). Most farmers have problems with stocking
densities as well as favourable rearing facilities for fry
rearing. The present study was carried out to investigate
the effect of stocking density and rearing facility on
the growth and economic potential of
T. rendalli
fingering production.
Methodology
The present study was carried out at the National
Aquaculture Centre in Domasi, Zomba, from January
to March 2014.
T. rendalli
fry of 0.9±0.1g average
weight from National Aquaculture Centre hatchery
were stocked in 1x1x1 m outdoor concrete tanks and
1x1x1 m hapas mounted in a 650 m
2
pond at a space
of 1m between hapas, at the stocking density of 30, 60
and 90 fry/m
3
designated as Treatments: T
1
, T
2
and T
3
respectively in three replicates. Local feed (CP; 18%)
was administered at 5% body weight three times a day
for three months. Initial weight and length of fry was
recorded at the start of the experiment followed by
monthly sampling to assess the fish's growth with a
sample size of 30, 60 and 90 fish for T
1
, T
2
and T
3
respectively. At close of three months, the experimental
fish was harvested and final body weight and length
recorded. Dissolved oxygen, pH and temperature were
recorded twice a day (8am and 2 pm) in the entire
experimental period using HANNA Multi-parameter
HI 8424.
Growth indices were calculated using the following
formula:
Specific Growth Rate (SGR) = [Ln(Wf) – Ln(Wi) /
Time (days)] x 100
Where Wf is Final average weight, Wi is Initial
average weight, Ln is Natural logarithm and Time is
Number of experimental days.
Average Daily Gain (ADG) = Wt
2
– Wt
1
/t
Where Wt
2
is final mean weight of fish at time t
2,
Wt
1
is Initial mean weight of fish at time t
1
and t is time in
days.
Weight Gain (WG) = Wt
2
– Wt
1
Where Wt
2
is final mean weight of fish at time t
2,
and
Wt
1
is Initial mean weight of fish at time t
1
.
Biomass (BM) = Wt
2
x N
2
Where Wt
2
is final mean weight of fish at time t
2
, and
N
2
is fish that survive until the end of the time interval
(t
2
).
Profit index was used as an economic indicator using
the following formula as adopted from (Ita and Okeoye,
1988).
Profit index = value of fish crop / total cost of feed
Data Analysis
Data on growth and profitability were analyzed using
Two-Way Analysis of Variance (ANOVA) at 95%
confidence interval. Least Significant Difference (LSD)
was used to separate the means among stocking
densities and within rearing facilities. Statistical Package
for Social Scientists (SPSS) 16.0 was used for the
analysis.
Results and Discussion
Growth and Economic Parameters
To assess
T. rendalli
fry growth within the treatments,
SGR, ADG, WG, MBW, BM and Lt for both tanks and
hapas-in-ponds were calculated and presented in Table
1 and Figure 1.
Table 1: Growth (g) of
T. rendalli
fry in the two rearing facilities under three stocking densities
Parameter
Treatments
Tanks
Hapas
30
60
90
30
60
90
Specific Growth Rate
2.12
1.68
1.52
2.54
1.98
1.44
Average Daily Growth
0.03
0.02
0.02
0.04
0.03
0.02
Weight Gain
1.07
0.86
0.75
1.6
1.1
0.71
Mean Body Weight
1.87±.06
1.76±.05
1.65±.04
2.51±.08
2.01±.09
1.62±.07
Biomass
56.10
105.60
148.50
75.30
120.60
145.80
Length
4.43±.04
4.35±.03
4.31±.03
5.11±.06
4.68±.08
4.43±.06
