International Journal of Aquaculture, 2017, Vol.7, No.13, 86-93
88
2.5 Fish stocking and biometry
In experiment 2, fish of av. length 6.5±0.15 cm and av. wt. 5.83±0.23 g were stocked at a density of 1 per m
2
,
employing the three selected substrates viz. bamboo, ambay and leucaena in triplicate. A set of 3 tanks without
substrate served as the control.
Biometry was performed at the beginning of the experiment and every thirty days until termination. Twenty fish
from each replicate was weighed on an electronic balance (accuracy 0.1 g) and standard length was measured. In
addition to weight and length, specific growth rate, survival, gross production and weight gain were determined at
the end of the 120-day experiment as follows.
Specific growth rate (SGR) = [(ln Final weight - ln Initial weight/ Experimental duration in days)] × 100
Survival (%) = Number of live fish harvested / Number of fish stocked x 100
Gross production (g) = Av. body weight at harvest (g) x Total number of fish harvested
Percentage weight gain = Final weight - Initial weight / Initial weight x 100
2.6 Statistical analyses
One-way ANOVA (P<0.05) as described by Chambers et al. (1992) was used to check the effect of treatments on
water quality variables, periphyton biomass and biochemical composition and fish growth parameters.
3 Results
All the water quality parameters monitored over the duration of the 2 experiments were within the limits suitable
for aquaculture. They ranged as follows: dissolved oxygen 6.71-7.32/6.91-7.17 mg/L, pH 8.22-8.68/8.16-8.52, EC
58.56-63.15/62.33-65.35 µS/cm², temperature 28.36-29.85/27.86-29.28°C, total alkalinity (CaCO
3
) 23.15-26.52/
31.15-36.19 mg/L, nitrite N (NO
2
) 0.01-0.03/0.04-0.05 mg/L, nitrate N (NO
3
) 0.95-1.35/1.39-1.78 mg/L,
ammonia (NH
3
) 0.24-0.38/0.23-0.83 mg/L, and phosphate (PO
4
) 1.82-2.69/1.13-1.29 mg/L (Table 1; Table 2).
Table 1 Physico-chemical parameters (mean ± SD) of water monitored in Experiment 1
Parameter
Control
Bamboo
Ambay
Leucaena
DO (mg/L)
6.71±0.16
a
7.32±0.13
b
7.09±0.12
ab
7.11±0.15
ab
pH
8.68±0.17
a
8.25±0.05
a
8.36±0.14
a
8.22±0.16
a
EC (µS/cm²)
58.56±3.22
a
63.15±2.32
a
61.73±4.25
a
62.67±1.85
a
Temperature (
◦
C)
29.85±0.38
b
28.62±0.12
a
28.45±0.38
a
28.36±0.24
a
Alkalinity (mg/L)
23.15±1.33
a
26.52±1.45
a
25.19±1.85
a
24.19±1.38
a
NO
2
(mg/L)
0.01±0.00
a
0.02±0.00
a
0.03±0.01ª
0.02±0.00
a
NO
3
(mg/L)
1.29±0.22
a
1.35±0.31ª
0.95±0.20
a
1.16±0.28ª
NH
3
(mg/L)
0.38±0.18
a
0.24±0.12ª
0.33±0.16
a
0.30±0.15
a
PO
4
(mg/L)
1.82±0.31
a
2.32±0.25
a
2.19±0.20
a
2.69±0.24
a
Note: Experimental duration 45 days. Values with the same superscript in each row are not statistically different (P> 0.05)
Table 2 Physico-chemical parameters (mean ± SD) of water monitored in Experiment 2
Parameter
Control
Bamboo
Ambay
Leucaena
DO (mg/L)
7.17±0.21
a
6.98±0.11
a
7.01±0.12
a
6.91±0.16
a
pH
8.16±0.27
a
8.52±0.15
a
8.27±0.18
a
8.42±0.12
a
EC (µS/cm²)
63.56±2.24
a
65.35±2.12
a
62.33±2.25
a
62.87±2.28
a
Temperature (
◦
C)
29.28±0.38
b
28.12±0.12
a
28.27±0.08
a
27.86±0.14
a
Alkalinity (mg/L)
31.15±1.62
a
34.52±1.24
a
36.19±1.58
a
34.19±1.83
a
NO
2
(mg/L)
0.05±0.01
a
0.04±0.01
a
0.04±0.01ª
0.04±0.01
a
NO
3
(mg/L)
1.78±0.16
a
1.56±0.22ª
1.39±0.14
a
1.42±0.32ª
NH
3
(mg/L)
0.83±0.12
b
0.27±0.09
a
0.23±0.06
a
0.34±0.08
a
PO
4
(mg/L)
1.28±0.11
a
1.13±0.15
a
1.29±0.12
a
1.26±0.14
a
Note: Experimental duration 120 days. Values with the same superscript in each row are not statistically different (P> 0.05)
