International Journal of Aquaculture, 2015, Vol.5, No.22 1
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Table 2 Growth, production, feed conversion ratio and survival rate, for Nile tilapia
O. niloticus
(Average initial wt. 30.2 g/fish)
reared in floating cages for a period of 196 days at different stocking rates
Item
Stocking density (fish/m
3
)
25 (S1)
50 (S2)
100 (S3)
150 (S4)
Initial Avg. wt., g/fish
30.01
9.4
30.08
7.6
30.20
8.5
30.10
9.2
Avg. Final weight
1
, g/fish
174.8
63.2
a
163.5
41.3
ab
151.7
40.6
b
147.2
42.3
b
Gain in weight, g/fish
144.7
54.1
a
133.4
33.7
ab
121.5
32.3
b
117.1
33.9
b
Daily gain
2
(g/fish)
0.86
0.32
a
0.79
0.20
ab
0.72
0.19
b
0.60
0.17
c
Avg. Gain in weight %
478.2
57.8
a
443.3
52.3
b
406.9
31.3
c
392.9
57.6
c
Initial avg. length (cm)
12.41
1.12
12.14
0.74
12.39
1.14
12.24
0.83
Final Avg. length (cm)
19.62
2.62
a
19.10
1.24
ab
18.46
1.78
bc
18.07
1.62
c
Gain in length (cm)
7.21
1.55
a
6.97
0.59
a
6.08
0.70
b
5.83
0.81
b
Gain in length %
57.5
7.60
a
57.40
3.20
a
49.1
3.10
b
47.5
3.50
b
Initial biomass/cage kg
0.750
0.06
1.505
0.07
3.020
0.11
4.515
0.15
Total crop /cage kg
4.371
1.60
d
8.173
2.10
c
15.171
4.10
b
22.086
6.30
a
Net production / m
3
3.620
1.40
d
6.668
1.70
c
12.154
3.20
b
17.571
5.10
a
Total feed intake (g/fish)
260.6
14.7
a
242.7
19.7
ab
225.2
15.5
b
222.6
12.6
c
Feed conversion ratio
5,
FCR
1.80
0.10
c
1.82
0.06
b
1.85
0.01
a
1.90
0.03
a
Specific growth rate
4
,SGR % /day
1.04
0.06
a
1.01
0.06
b
0.97
0.04
c
0.95
0.07
c
Condition factor
5
(K)
2.23
0.16
c
2.31
0.23
bc
2.37
0.18
ab
2.43
0.13
a
No. of fish / cage
25
50
100
150
Survival rate
6
, SR %
100
100
100
100
*Means in the same rows having different superscript letters were significantly different at 0.05 levels.
1. AFW (g/fish) =Average final weight (g) – Average initial weight (g).
2. ADG (g/fish/day) = 100[AFW (g)/experimental period (d)].
3. FCR = DM Feed Intake (g)/Live weight gain (g).
4. SGR (%/day) = 100(Ln final weight–Ln initial weight)/experimental period (d)).
5. Condition factor “K”, K=W/L³ ×100,where: W= weight of fish, g L= total length, cm
6. SR =100 [Total No of fish at the end of the experiment/Total No of fish at the start of the experiment]
Figures 1 (A) The relation between total production and stocking
density. (B) The relation between mean weight per fish at
harvest and stocking density
Figures 2 Changes of mean body weight of fish (g) during
different periods of the present study as influenced by stocking
density
to lower or medium fish density groups. Condition
factor was increased significantly (
P
<0.05) by increasing
stocking rates of fish from 25 to 150 fish/m
3
.
Economic efficiency for Nile tilapia reared at four
stocking densities was presented in Table 3. The obtained
