International Journal of Aquaculture, 2015, Vol.5, No.3 1
-
13
6
Table 3 Effects of stocking density and water exchange rate on mono-sex Nile tilapia,
O. niloticus
gain in weight (g), gain in weight
(%), gain in length (cm/fish), gain in length (%) after 44 weeks of rearing in concrete tanks. Values are means
SE
Classification
Average gain in weight
Average body length
(g/fish)
(%)
(cm/fish)
(%)
Stocking density
**
**
**
**
50 fish/m
3
211.4
10.9
2817.8
145.3
a
13.6
0.4
a
149.5
5.6
a
75 fish/m
3
156.0
7.9
2080.3
105.2
b
11.9
0.3
b
133.2
3.0
b
100 fish/m
3
124.8
6.5
1664.3
86.2
c
10.1
0.3
c
113.1
3.6
c
Water exchange
N.S.
N.S.
N.S.
N.S.
8 liter/min.
168.8
8.7
2250.3
116.0
11.8
0.3
130.4
4.2
12 liter/min.
159.4
8.1
2124.7
107.6
11.9
0.3
133.4
3.7
SD x WE
N.S.
N.S.
N.S.
N.S.
R
2
0.31
0.0.31
0.33
0.25
Note: 1. Significant level: N.S. = P
0.05, * = P
0.05, ** = P
0.01. 2. Means that have the same superscript letters within each
classification column are not significantly different from each other. 3. SD = Stocking density; WE = water exchange
Table 4 Effects of stocking density and water exchange rate on mono-sex Nile tilapia,
O. niloticus
average daily gain (g/fish/day),
specific growth rate (% /day) and condition factor (K) after 44 weeks of rearing in concrete tanks. Values are means
SE
Classification
Average daily gain (g/fish/day) Specific growth rate (%/day)
Condition factor (K)
Stocking density
**
**
N.S.
50 fish/m
3
0.68
0.04
a
1.08
0.02
a
1.08
0.02
75 fish/m
3
0.51
0.03
b
0.98
0.02
b
1.90
0.11
100 fish/m
3
0.41
0.02
c
0.91
0.02
c
1.88
0.03
Water exchange
N.S.
N.S.
N.S.
8 liter/min.
0.55
0.03
1.00
0.02
1.95
0.06
12 liter/min.
0.52
0.03
0.98
0.02
1.82
0.05
SD x WE
N.S.
N.S.
N.S.
R
2
0.31
0.28
0.25
Note: 1. Significant level: N.S. = P
0.05, ** = P
0.01. 2. Means that have the same superscript letters within each classification
column are not significantly different from each other. 3. SD = Stocking density; WE = water exchange
stocking density grows faster and had a daily gain
and specific growth rate of 0.68 (g/fish) and 1.08
(%/day), respectively, while the highest stocking
density grows slower and had a daily gain and
specific growth rate of 0.41 (g/fish) and 0.91,
respectively. Condition factor (K) was not influenced
significantly by either stocking density or water
exchange rate. The means of condition factor were
1.86, 1.90 and 1.88 for stocking density of 50fish/m
3
,
75 fish/m
3
and 100 fish/m
3
, respectively. The means
of condition factor were 1.95 and 1.82 for water
exchange rates of 8L/min. and 12 L/min., respectively.
There were no significant interaction between
stocking density and water exchange rate in terms of
average daily gain, specific growth rate and condition
factor. There were a correlation between stocking
density and average daily gain (g/fish) and specific
growth rate (SGR %/day). When the stocking density
were increased the average daily gain and specific
growth rate of fish were decreased.
Effects of stocking density and water exchange rates
on mono-sex Nile tilapia,
O. niloticus
total production
and net production (kg/m
3
) after 44 weeks of rearing
in concrete tanks are presented in Table 5.
It can be
concluded from this table that, total production (kg/m
3
)
and net production (kg/ m
3
) of the present experiment
provided a picture for the stocking density and growth
rate (Figure 3 & 4). Total production (kg/m
3
) and net
production (kg/m
3
) were significantly (P
0.01) the
best at the highest stocking density (100fish/m
3
).
Harvests and production estimates increased with
increasing stocking density. No significant differences
(P
0.05) were found between water exchange rates
in terms of total and net production (kg/m
3
). At the
end of the experiment, total production was 10.97
kg/m
3
at the lowest stocking density and 13.23 kg/m
3
at the highest stocking density. Production was
opposite to the individual weight during the growth
period, that the individual weight decreased with the
increasing stoking density (Figure 3 & 4 and Table 5),
