International Journal of Aquaculture, 2017, Vol.7, No.13, 86-93
90
Table 5 Growth performance of jaraqui (mean±SD) over the culture period under different treatments
Parameter
Control
Bamboo
Ambay
Leucaena
Final av. weight (g)
19.44±1.12
a
34.34±2.05
d
29.85±1.71
c
24.38±1.65
b
Final av. length (cm)
9.02±0.17
a
11.23±0.69
b
10.14±0.52
ab
9.21±0.25
a
Survival (%)
95.00±2.31
b
100.00±0.00
c
90.00±2.62
ab
85.00±3.33
a
Gross production (g/100m
2
)
1846.80±33.26
a
3440.00±45.49
d
2686.50±26.93
c
2072.30±38.15
b
Net weight gain (g)
13.61±1.31
a
28.51±1.53
d
24.02±1.21
c
19.00±0.57
b
SGR (%/day)
1.00±0.02
a
1.48±0.01
d
1.36±0.02
c
1.19±0.01
b
Weight gain over control (%)
--
76.65
53.55
25.41
Note: Initial av. length of fish was 6.5±0.15 cm and initial av. wt. 5.83±0.23 g. Values with the same superscript in each row are not
statistically different (P>0.05)
4 Discussion
The physico-chemical parameters of aquatic ecosystems serve as water quality indicators. Water quality of fish
ponds is influenced by various factors that include the feeding habit of the cultivated species, stocking density,
and the quality and quantity of nutrient input through fertilizer and feed. Decomposition and accumulation of
organic matter also affects water quality (Asaduzzaman et al., 2009). Inadequate conditions of water quality affect
growth, reproduction, health, survival and quality of fish life, jeopardizing the success of aquaculture (Lourenco et
al., 1999). The water quality parameters monitored in the present study were within the acceptable range for fish
culture, as reported by Boyd (1981) and Tavares (1994). According Proença and Bittencourt (1994), the optimal
level of oxygen for tropical fish species is in the range of 4 to 6 mg/L. In the current experiments, dissolved
oxygen remained above 6 mg/L throughout. pH of pond water was in the alkaline range, the value remaining
higher than 8 over the duration of the two experiments. Gangadhar and Keshavanath (2012) obtained good growth
of rohu (
Labeo rohita
) in ponds with alkaline pH (8.39 to 9.82). Araujo-Lima and Goulding (1997) observed that
in nature, jaraqui tolerates large ionic plasticity and survives well even in acidic waters, such as the Solimões river
black water (pH 4.5) as well as white water (pH 6.5 to 7). EC was low in both the experiments (Table 1; Table 2).
Tavares (1994), who recorded EC of 23-71 μS/cm
2
in fish ponds, opined that the values can be used as a reference
to assess the availability of nutrients and regulate the concentration of ions in th e water column. The average
water temperature was between 27°C and 29°C during the present study, being within the desired range. Proença
and Bittencourt (1994) stated that temperature in the range 20°C to 30°C is acceptable in fish cultivation, but the
ideal range is from 25°C to 28°C. Jaraqui is found in nature in both lotic and lentic ecosystems, where the
minimum temperature is 24°C and maximum 40°C, indicating high temperature tolerance (Araujo-Lima and
Goulding, 1997). Temperature remained significantly lower in the substrate tanks. This can be attributed to the
shading of these tanks by the substrates as reported earlier by Keshavanath et al. (2002). Alkalinity acts as a pH
regulating buffering system of pond water (Tavares, 1994). When alkalinity (CaCO
3
) is low (less than 20 mg/L), it
can cause high fluctuations in pH index, hindering the performance and production of fish, due to the constant
adaptation needs of the animal by osmotic exchange with the medium (Boyd, 1981). The values of nitrogen
compounds NO
2
, NO
3
and NH
3
were low (Table 1; Table 2). For fish, these are toxic in water when the
concentration crosses 0.5 mg/L (Ostrensky and Boeger, 1998), 5 mg/L and 2 mg/L respectively (Tavares, 1994).
Ammonia values in experiment 2 showed a decline in substrate treatments which is attributable to its uptake by
periphyton and plankton (Azim and Little, 2006).
Periphyton biomass on different substrates can be quite varied and is influenced by environmental (temperature,
photoperiod) and operational (grazing pressure, fertilization, fish stocking density, density and type of substrate,
etc.) processes (Azim et al., 2005). The average periphyton biomass recorded on bamboo, ambay and leucaena
substrates was 1.12±0.16, 0.95 ±0.13 and 0.87±0.11 mg/cm² in experiment 1 and 1.43±0.22, 1.22±0.14 and
0.98±0.16 mg/cm² in experiment 2. The higher values recorded in experiment 2 could be related to the longer
duration of the study and grazing by the fish stocked. Grazing is known to improve periphyton growth (Jacoby,
1987; Swamikannu and Hoagland, 1989). These values compare with those observed on glass (0.91 mg/cm
2
),
