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International Journal of Aquaculture 2012, Vol.2, No.9, 59
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64
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61
Figure 1 Mean body weight of juvenile
Oreochromis niloticus
reared at different water temperature in degree Celsius during
90 day experimental period
The mean values of pH ranged from 8.18 to 8.32 were
optimum for rearing juvenile
Oreochromis niloticus
.
These results were in agreement with the work of
El-Sherif and El-Feky (2009a), who reported that the
optimum pH values for optimum growth and feed
utilization efficiency were between 7 and 8. The
present results also showed that the range of dissolved
oxygen concentration were from 5.7 to 6.7 mg/L
which confirmed the earlier work of El-Sherif and
El-Feky (2009b). These authors reported that
fingerling of
Oreochromis niloticus
showed the best
growth performance and feed utilization efficiency
when dissolved oxygen concentration ranged from 6.5
to 6.7 mg/L. The work of Bahnasawy et al (2003) also
confirmed the present results that the pH values
ranged from 6.1 to 7.63 and dissolved oxygen
concentration ranged from 6.1 to 8.4 mg/L were
suitable for optimum growth performance and feed
utilization efficiency of
Oreochromis niloticus
. In
general, with the exception of water temperature, the
water parameters for all aquaria were not significantly
different (p>0.05). Moreover, the initial mean body
size of juvenile
Oreochromis niloticus
was
homogenous. Thus, variation in growth performance
and feed utilization efficiency were caused due to
differences in water temperatures.
2.2 Growth performance
Growth performance and feed utilization efficiency of
juvenile
Oreochromis niloticus
reared at different
water temperature treatments (24, 26, 28 30, 32 and
34
℃
) were significant (p<0.05). The highest final
mean body weight of the fish was achieved at 32
℃
water temperature followed by 30
℃
water
temperature. Lower (24
℃
) and higher (34
℃
) water
temperature caused reduction of final mean body
weight of juvenile
Oreochromis niloticus
by 48.78%
and 24.63%, respectively, which was attributed to a
decrease in feed utilization efficiency and metabolic
process (Larsson and Berglund, 2005).
Similarly, the highest mean body weight gain and
specific growth rate were observed on the fish reared
at 32
℃
followed by 30
℃
water temperature and
were significantly different (p<0.05) from the fish
reared at the rest of water temperatures. In this study,
growth performance of juvenile
Oreochromis niloticus
in terms of the final mean body weight, mean body
weight gain and specific growth rate increased
gradually and reached to their maximum values at 32
℃
water temperature and decreased at 34
℃
water
temperature.
These results are in agreement to the
earlier works of Saber et al (2004), El-sherif and
El-Feky (2009a,b) and Pandit and Nakaura (2010),
who reported that growth performance of juvenile
Oreochromis niloticus
reared at different water
temperature increased as water temperature increased
until 30
℃
to 32
℃
and declined when it excided. The
present results were also confirmed the earlier works
of Devline and Nagahama (2002) and Azaza et al
(2008) who stated that lower and higher water
temperature reduces the growth performance of
juvenile
Oreochromis niloticus
. As mentioned by
Azaza et al (2008), juvenile
Oreochromis niloticus
reared at 26
℃
and 30
℃
water temperature has
higher body weight than reared at 22
℃
and 34
℃
water temperature. The results of the present study
were also in line with the work of Pandit and Nakaura
(2010), who reported that the growth performance of
juvenile
Oreochromis niloticus
reduced at 35
℃
and
37
℃
water temperature as compared to 27
℃
and 32
℃
water temperature.