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International Journal of Aquaculture, 2014, Vol.4, No.22 1
-
6
http://ija.biopublisher.ca
4
The average water temperature was 22.44 °C, while
pH varied between 7.30±0.12 and 7.81±0.16 across all
the treatments. The minimum and maximum DO
concentration varied between 5.98±0.33
mg L
-1
and
6.13±0.36 mg L
-1
across all treatments, respectively.
The unionized ammonia varied between 0.0057 mg
L
-1
and 0.0354 mg L
-1
.
Discussion
From the results presented above, there were
differences in the growth of fish in all the treatments.
The differences in growth and survival were mainly
due to the different levels of ammonia in the water.
Rapid and slow growth was observed in T4 (0.48 kg
quail manure/week) and 5 (0.64kg/ quail manure/
tank/week) respectively.
The study demonstrated that higher amounts of
ammonia affected growth and survival of the fish in
treatment 5 (T5), a tank with the highest amount of
quail manure added per week. However, T1, T2 and
T3, showed constant growth till the end of the
experimental period, with no significant differences
observed among them (Fig. 1). The growth rate of fish
in fertilized tanks was partly attributed to the leftover
feed from the quails and the fertilization of the water
which stimulated the growth of phytoplankton and
zooplankton. In order to reduce expenses on
commercial fish feed, supplementary ingredients in
use among the farmers have also included: soybeans,
maize bran, other various plant proteins, insects and
algae. These have grown fish to attain table size of
between 100 and 350g. However, it must be
emphasized that consumer preference in Zambia
differs a lot and size of fish on the market does not
matter much.
Results of the experiment showed that in order to
achieve acceptable fish growth and survival of fish,
0.48 kg quail manure/week/2m
2
should be used as
optimum for better growth of fish, although no
primary productivity was measured to estimate
zooplankton biomass in this study. At that level,
growth performance was good and other indicators
were well within acceptable range of fish of the same
size. Similarly, Nile tilapia (
O. niloticus
) fingerlings
averaging 19.0± 1.0 g in weight were reared at four
different concentrations of UIA-N (0.01, 0.05, 0.1 and
0.15 mg/l) besides the control using 15 glass aquaria
(40 ×70 ×60 cm) (El-Sherif, and El-Feky, 2008). At
the end of the experimental period (after 75 days from
the stocking) the final average body weights (FBW) of
Nile tilapia (
O. niloticus
) fingerlings were 37.2, 36.4,
32.5, 26.9 and 37.7 g for UIA-N concentrations of
0.01, 0.05, 0.1, 0.15 and 0.004 mg/l, respectively
(El-Sherif, and El-Feky, 2008).
In this study, all treatments, except 5, recorded high
survival rate (Table 1), while El-Sherif, and El-Feky
(2008) reported that no mortality occurred in any of
their experimental groups throughout the experimental
period. The use of quail manure which was rich in
proteins underwent decomposition and the end
product was ammonia which contained unionized
ammonia. Ammonia exists in two forms: unionised
ammonia (NH3-N), and ionised ammonia (NH
4
+-N),
the sum of these two is called total ammonia nitrogen
(TAN) (Molleda,
et al
., 2007). The relative concentration
of ammonia is primarily a function of water pH,
salinity and temperature (Pillay and Kutty 2005). The
higher toxicity levels of NH
3
-N and CO
2
in water
depends on the water’s pH controls acid-base
equilibrium; as an example, at 20
o
C and a pH of 7.0,
the mole fraction of NH
3
-N is 0.004, but at a pH of 10,
the NH
3
-N increase to 0.8 at the same temperature
(Timmons
et al
., 2002).
Based on the results obtained, the ammonia level was
highest in T5, which could have been toxic, eventually
affecting growth and survival rate of fish in the tank.
Higher mortalities in T5 could equally, be attributed to
the high amount of ammonia levels recorded, although
the values were below unionized Ammonia of 0.05 mg
L
-1
that may harm fish. Normally, warm water fish are
more tolerant to ammonia toxicity than coldwater fish,
and freshwater fish are more tolerant than saltwater
fish, so in general, NH
3
-N concentrations should be
held below 0.05 mg L-
1
and TAN concentrations
below 1.0 mg L-
1
for long-term exposure (Timmons
et
al.,
2002). During the day especially after adding quail
manure some fish would be seen coming to the
surface gasping for air, showing signs of loss of
appetite and red streaking on the fins, gills turning red
at the same time fish appearing lethargic. These results
were in line with a study conducted by Ogbonna and
Chinomso (2010) on Ammonia poisoning and it was
concluded that ammonia poisoning could happen
suddenly, or over a period of days. Similarly, a study