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International Journal of Aquaculture, 2014, Vol.4, No.22 1
-
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http://ija.biopublisher.ca
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aquaculture (Thorarinsdottir et al., 2011). In recent
years most farmers have engaged in the integration of
fish and quail rearing. The use of quail manure as a
fertilizer to enhance the growth of phytoplankton in
ponds raises a lot of concerns due to ammonia in quail
manure which could potentially affect the growth and
survival rate of fish, (Jobling, 1994; Durborow
et al
.
,
1997). Ammonia toxicity to fish depends on the
concentration of unionized ammonia (NH
3
) (Handy &
Poxton, 1993). Percent NH
3
increases with temperature
and pH. Both temperature and pH increase the NH
3
concentration (Nettena
et al
, 2013). In general, more
NH
3
and greater toxicity exists at higher pH, which
implies that NH
3
is more dependent of pH than
temperature. This is because the percent of toxic
un-ionized NH
3
increases with pH (Frank, 1998). NH
3
toxicity will become more pronounced under higher
temperatures, but that effect on aquatic macrophytes
will strongly depend on pH of the water layer and
specific metabolic adaptations of different species
(Nettena
et al
, 2013). However, less concentration of
this NH
3
can be tolerated at lower pH (Frank, 1998).
Materials and Methods
The experiment was conducted in duplicates using
10 × 2m ×2m (4m
2
) concrete tanks at The National
Aquaculture Development and Research Centre
(NARDC) in Mwekera for a period of 14 weeks. The
ponds were supplied with borehole water that was
maintained at constant level throughout the
experimental period. Twenty-five fish (
Tilapia
rendalli
), with an average individual initial weight of
14 g and 79.49 mm length, were stocked per tank.
Tilapia rendalli
fingerlings that were used in the
experiment were collected from a 150 m
2
hatchery
earthen pond located within the fish farm. Fingerlings
were acclimatized for a period of one week before the
commencement of the experiment. During the
acclimatizing period, the fingerlings were fed on
maize bran at 4% of their body weight.
Key water quality parameters such as water
temperature, pH and dissolved oxygen (DO) were
measured twice per day (at 09:00hrs and 15:00hrs),
using a Horiba U-10 water quality checker. The
checker sensor measures by being directly submersed
or dipping the probe 20 cm into the water. Total
ammonia-nitrogen was monitored twice a week using
standard methods (Tucker, 1993; APHA, 1999).
Every fortnight individual fish were weighed on a
sensitive scale and the length measured on a
measuring board to the nearest 0.1 cm. For accurate
results the fish were starved for 24 hours prior to
weighing. The growth of fish was compared in tanks
with different amounts of quail manure. Initial and
final weight, percent in weight gain, increase in total
length, and coefficient of the final weight of
individual and condition factor were analyzed using
analysis of variance (ANOVA).
The growth parameters were calculated using the
following formulae:
Conditional factor (K): The formula is of the form:
K=W/L
3
Where K = Fulton’s condition factor, W = the weight of
the fish, and L is the length (usually total length).
Specific growth rate (SGR), expressed as percent body
weight per day, was calculated from: SGR = 100 (ln Wf
– ln Wi)/t
Where:-
Wf = final mean weight,
Wi = initial mean weight, and
t = experimental time in days
Percentage increase in weight (IWG %) was computed
following the formula provided by De Silva and
Anderson (1995): %IWG = (W
f
- W
t
)/W
t
x100
The experiment was a completely randomized design
(CRD) with five treatments; T1 (control, without quail
manure), T2 (0.32kg quail manure/tank/week), T3
(0.40kg quail manure/ tank/week), T4 (0.48kg quail
manure/tank/week) and T5 (0.64kg quail manure/tank/
week), replicated two times.
Statistical package for social sciences (SPSS) version
12.0 software was used in the statistical analysis and
variables differences were considered significant at P
< 0.05. One–way analysis of variance (ANOVA) was
used to test the differences between treatments during
the experiment.
Results
As shown in Figure 1, there were differences in the
final mean weight gain among the treatment groups.