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International Journal of Aquaculture, 2014, Vol.4, No.02,
http://ija.sophiapublisher.com
2
Despite the increasingly wide use of the mixo-haline
rotifer
B. plicatilis
in the marine fish laviculture, there
are no records on the culture and use of the fresh
water
B. plicatilis
as live feed in the fresh water fish
larviculture. Therefore, any efforts to culture the fresh
water rotifer
B. plicatilis
and its consecutive use in the
rearing of any of the fresh water fish larvae would be
appreciated as important to the large scientific
community of the world.
Currently, as aquaculture industry is expanding, also
the technologies in processing fish feed into various
formulations including the micro-dry diets for fish
larvae are also increasing. In East Africa, some local
fish farmers use boiled chicken egg yolk for the
rearing of
C. gariepinus
larvae. However, the feed has
never been researched and recommended for its
suitability. Chicken egg yolks are appreciated of
having diversity of nutrients like vitamins, amino
acids, and high content of lipids, however with a bit
low protein content as compared to the high demand
of
C. gariepinus
larvae (Krawczyk, 2009). Therefore,
any efforts to experiment the suitability of the feed in
the growth and survival of the larvae would be
appreciated by many as important especially in the
regards of promoting local technologies and
innovations. Generally, East African aquaculture
industry is relatively undeveloped despite of much
potential for its growth. In those countries, of the
major obstacles towards the growth and ultimate
development of the industry is the unavailability of
cheap technologies in place to lead into affordable
quality fish feed and seed (Mwanja et al., 2006; FAO,
2006). And, knowledge on the technical knowhow in
artificially manipulation of
C. gariepinus
broods to
lead to larvae and its rearing processes is limited. In
West Africa (i.e. Nigeria), Artemia feeds (decapsulated
from its cysts or packed as dry diets) are the most
widely used feeds for the rearing of larvae of
C.
gariepinus
and its hybrid, Heterobrachs (Olurin and
Oluwo, 2010; Olurin et al., 2012).
This study intended at mass producing the fresh water
rotifer
B. plicatilis
and explores its performance on the
rearing of
C. gariepinus
larvae. The performance
indices monitored were growth rate (GR), Specific
Growth Rate (SGR), survival percentages, and
conditional factor (CF). The study also explored the
performance of chicken egg yolk on the rearing of the
same
.
The hypotheses of the study are: (a) Rotifers
can offer proper growth in the
C. gariepinus
larvae (b)
Egg yolk perform well in the rearing of African catfish
larvae, thus can be a good substitute for live feeds.
1 Results
During the 1
st
phase of the experiment, there were
significant differences (F = 768, p < 0.01, Table 1) in
growth performances of the three feeds fed to the
African catfish larvae. The African catfish larvae fed
with egg yolk indicated the highest growth rate
(60.42%/day), survival of 83% and SGR of 0.28. In
terms of growth rate (42.76%/day), the larvae fed with
mixture of egg yolk and rotifer performed the second
to egg yolk. The feed indicated survival rate of 87%
and SGR of 0.23. The larvae fed with rotifer indicated
the poorest growth rate (25.76%/day) and SGR (0.16),
however with highest survival percentages (98%)
(Table 1).
Table 1 Growth rate, SGRs, and survival percentages of the
Clarias gariepinus
larvae fed with chicken egg yolk, rotifer
(
Brachionus plicatilis
) and a mixture of the two during the 1
st
phase (the first five days) of the experiment.
Egg yolk
Egg yolk
+ Rotifer
Rotifer
Initial average
weight (mg)
3.33 ± 0.13 3.33 ± 0.13
3.33 ± 0.13
Final
average
weight (mg)
13.39 ± 2.87 10.45 ± 1.80 7.62 ± 2.45
Initial average
length (mm)
5.83 ± 0.75 5.83 ± 0.75
5.83 ± 0.75
Final
average
length (mm)
9.65 ± 1.16 8.95 ± 0.59
8.20 ± 0.42
Growth
rate
(%/day) (sd)
60.42
a
42.76
b
25.76
c
Survival
(%)
(nsd)
83
a
87
a
98
a
SGR (sd)
0.28
a
0.23
b
0.16
c
Condition factor
(CF) (nsd)
1.49
a
1.46
a
1.38
a
Note: Values with same superscript in a row mean that were not
significant different.
During the 2
nd
phase (weaning) of the experiment,
there were significant differences in growth
performances of the African catfish larvae (F = 418,
p < 0.01, table 2) with larvae fed on egg yolk
performing best (weight and length of 19.85±3.66mg
and 12.13±0.60mm, respectively, and survival of
61%). The performance of larvae fed with mixture of