International Journal of Aquaculture, 2015, Vol.5, No.24 1
-
5
3
Figure 1
T rendalli
fry growth rate per stocking density within
rearing facilities
A two-way ANOVA was conducted to examine the
effect of stocking density and rearing facility on growth
of
T. rendalli
fry. There was significant interaction
between stocking density and rearing facility on
growth of
T. rendalli
fry,
F
(2, 12) = 17.132,
p = 0.001
.
Statistical significant differences were also observed in
both the rearing facility, F(1,12) = 1918.00,
p = 0.001
,
with fry reared in hapas mounted in pond (4.67±0.42)
growing better than fry reared in tanks (1.67±0.19).
Stocking density, F (2,12) = 17.61,
p = 0.001
, with fry
in T
1
(3.45±1.81) grew better than fry in T
2
(3.07±1.79)
and the least being T
3
(2.98±1.34). The results show
that rearing facility had more influence on fry growth
than stocking density. Rearing facilities play a great
role in fry growth as they provide a platform for natural
feed enhancement depending on the nature of the
facilities. The potential for enhanced primary productivity
in ponds made hapas mounted in pond more productive
compared to the tank. These results agree with Keremah
and Esquire (2014) who attributed the differences in
growth to the availability of natural food (plankton)
induced by decomposed and degraded uneaten artificial
feed for fish in the pond unlike in the tank, where the
fish relied solely on artificial feed as the only food
source. The availability of additional dietary protein
source may attribute to the highest SGR for fry reared
in hapas mounted in pond.
The results also show that growth performance of
T.
rendalli
fry is affected by stocking density. This is in
agreement with Mensah (2013) and (King et al., 2000)
who observed that social interactions through competition
for food and/or space negatively affect fish growth,
hence higher stocking densities lead to increased stress,
resulting into increase in energy requirements thereby
causing a reduction in growth rate and food utilization.
Stocking density is an important parameter which
directly affects the growth of fish and hence its
production (Backiel and Le Cren, 1978). Thus the
present study has demonstrated that fry in low stocking
densities grow faster hence attain fingerling stage
earlier than fry in high stocking densities. The results in
this study are in agreement with the findings of
Abdel-Hakim and Ammar (2005) who reported that
lower stocking densities resulted in significantly higher
final weights and lengths of fish compared with the
higher stocking densities.
To assess the profitability potential of the treatments,
economic parameters of production for both tanks and
hapas-in-ponds were calculated and presented in Table 2.
The results show that there were no statistically
significant interaction between the effects of stocking
density and rearing facility on profitability of
T.
rendalli
fry,
F
(2, 12) = 0.18,
p
= 0.98
. These results
show that both stocking density and rearing facility do
not affect profitability of fingering production. This
could be as a result of the pricing policy of fingerlings
where fingerings are sold in numbers and not biomass.
However, selling fingerlings after attainment of a
stock-able size, thus reducing the rearing time can limit
production costs and affect profitability, especially
with the fast growing hapas mounted in pond system.
Table 2: Profit index among the treatment groups
Treatment
Biomass (g)
Cost of feed (MK) Value of fingerlings (MK)
Profit index
Tank
30
25.40±0.35
421.99
450
1.29±0.02
a
60
52.00±2.77
794.33
900
1.26±0.07
a
90
92.70±28.84
1117.02
1350
1.12±0.30
a
Hapa
30
27.10±0.17
514.19
450
1.31±0.01
a
60
54.60±0.01
823.53
900
1.30±0.01
a
90
102.00±36.37
995.61
1350
1.12±0.33
a
Means with the same superscript on the same column are not significantly different at α = 0.05, 1USD=450MK
