International Journal of Aquaculture 2015, Vol.5, No.34, 1-7
6
Figure 6 Zooplankton abundance in P2
Figure 7 Zooplankton abundance in P3
4 Dissussion
Each aquatic organism has specific survival range of
environmental temperature for their efficient
existence and beyond the limit, the conditions become
lethal. Water temperature is known to prominently
affects the fish life by directly or indirectly through
influencing the physical and chemical properties of
the water in which it lives. Growth performance of
fish is dependent on the temperature (Britz et al., 1997;
Azevedo et al.,1998; Lei and Li, 2000) which in turn
is dependent on the altitude.
O. niloticus
fingerlings
were maintained in fish ponds located at altitudes of
2,500 masl, 2,100 masl and 1,710 masl fertilized with
organic fertilizer and supplementary feed. There was
a significant difference (P<0.05) in water temperature
among the treatments which caused variation in
growth performance of
O.niloticus
. In the present
experiment when the temperature increased growth
rate was observed in pond 3 located at low altitude
where the temperature was higher than pond1
indicating the influence of temperature on the growth
of
O. niloticus
. The highest weight gain was also
observed for the fish maintained in P3. Fish being
cold blooded, is easily influenced by the surrounding
water temperature that shows a prominent effect on
body temperature, growth rate, feed consumption,
FCR and other metabolic function[Lovell, 1989; lei
and Li, 2000). The present results revealed that when
the altitude is decreased the temperature increases and
as a result growth performance increases (El-Sherif
and El-Feky, 2009). The range of temperature in the
study sites varied between 21.6 and 27
o
C that
prevailed at the altitudes of 2,100 masl and 1,710
masl. It is inferred that the water temperature in the
low altitude was more favorable for the growth of
O.
niloticus
as reported earlier that the optimum water
temperature is between 21 and 28
℃
(Popma and
masser, 1999; Bhijikajee and Gobin, 1997).The
average body weight gain of the fish decreased on day
60 and 105 in P1, on day 90 in P2 due to low water
temperature. Similar findings on the average daily
body weight gain decrease at temperatures below
21.1
o
C was reported earlier (Khouraiba, 1989) which
may be attributed to decrease in feed consumption
and metabolic rate. An increase in temperature
enhances the activity of digestive enzymes, which
may accelerate the digestion of the nutrients, thus
resulting in better growth (El-Sherif and El-Feky,
2009). In the present study, SGR in the three
treatments were positively correlated with
temperature. There was a decrease in SGR at the
average temperature of 16.1°C (P1) and it was better
in P3 than P2. This observation is in agreement with
the specific growth rates observed by many workers
who stated that between 16 and 20°C SGR is
significantly (P < 0.05) high however it was highest at
25°C (El-sherif and El-Feky, 2009). The best FCR
was observed in P3, followed by P2 and P1 (Table 4).
The variation in water temperature also influences the
solubility of gases, pH, conductivity and plankton
distribution (Boyd, 1998). At the altitude of 2500
masl higher transparency and low concentration of
nitrate and total phosphorus was noticed associated
with low rate of decomposition of the organic manure
applied and the resultant
low rate of plankton
production. The plant nutrients nitrate and phosphorus
recorded in the ponds are however optimum for the
fish culture and phytoplankton growth (Boyd, 1998).
High abundance of plankton in P2 and P3 might be
due to the higher nutrient (nitrogen and phosphorus)
