Basic HTML Version
International Journal of Aquaculture, 2014, Vol.4, No.02,
http://ija.sophiapublisher.com
6
larvae tested for egg yolk was supplied with 100ml of
the solution. And those tested for egg yolk and
rotifers, the feed was mixed in a proportion of 1:5,
thus each tank was supplied with 50ml of solution of
egg yolk and 250ml of a solution of rotifer three times
a day. The amount of feed was adjusted as per the
larvae requirements with time and during each feeding
the larvae were fed to satiety. Some samples of the
dried
B. plicatilis
and egg yolk were taken to Sokoine
University of Agriculture (SUA) for proximate
analysis of crude protein, lipid, crude fibre, and ash
contents.
3.3 Set up and duration of the experiment
The feeds performance experiment lasted for 15 days
and was divided into two phases. The 1
st
phase which
comprised the first five days since the commencement
of exogenous feeding aimed at giving the larvae with
live feed parcel. The second phase (weaning period)
lasted for 10 days and aimed at acclimatizing the
larvae with a dry formulated diet. During weaning
period, the larvae were fed with the live feed plus the
Ugarchick (35% crude protein, 7% lipid, 6.5 % crude
fibre, 7% ash, and 11% moisture) in a substitution
manner. At the end of each phase, the larvae in the
nine tanks were randomly sub sampled to obtain 10
larvae from each tank, totalling to 30 larvae for each
feed treatment. The larvae were weighed to the nearest
0.0001mg (using a 220g capacity and 0.0001g
sensitivity balance, Model Sartorius, CPA 224S
23750418, USA). The total lengths were also
measured to the nearest 0.1 millimetre using a 30cm
ruler. The faeces and uneaten food at the bottom of
each tank including the dead larvae were pumped out
daily at 08.00hrs using a 1cm thick and 5m long pipe.
While the dead larvae were counted for the calculation
of survival %, the live larvae were separated from the
impurities and returned to the tanks.
3.4 Growth performance indices
Growth parameters were determined using both length
and weight following the formulas provided in Olurin
et al. (2012):
GR = 100
× (W
f
- W
i
)/(T x L
i
)…………………. (i)
GR = 100 × (L
f
- L
i
)/(T × L
i
)………............…… (ii)
SGR = (ln W
f
- ln W
i
)/(T
2
- T
1
)……………….... (iii)
SGR (mm/day) = (ln L
f
- ln L
i
)/(T
2
- T
1
) ………. (iv)
SR (%) = 100 × N
s
/N
i
…………….……………. (v)
Where GR = growth rate, SGR = specific growth rate,
SR = survival rate; W
f
= final weight (mg), W
i
= initial
weight (mg), L
f
and L
i
represent final and initial
lenghts in mm respectively; T = time in days, T
1
and
T
2
represents initial and final time (days); Ns and Ni
represents number of survivors and initial number of
fish respectively.
The condition factor of
C. gariepinus
larvae
was
calculated according to Madu et al
. (
2003):
CF = 100 × W/L
3
…………………..........………. (vi)
Where w = weight of fish in mg, L = length of fish in
mm.
3.5 Statistical analysis
One-way ANOVA test was used for the test of
significance in growth performance and water quality
parameter differences among the treatments. The
analyses were done using SPSS version 17 (SPSS Inc,
USA).
4 Conclusions
The rotifer
B. plicatilis
is not a suitable feed for the
larval rearing of farmed fresh water fish like African
catfish if profitability is important. Generally, because
both diets tested indicated poor growth and survival,
this study does not recommend any at first choice,
unless for assuring survival at risks of mortality. Of
the diets tested, chicken egg yolk can somehow work
well as a good start feed in the larvae rearing of
African catfish. While choosing feed for the larvae, it
is important that the regards of deterioration of water
quality are taken care, as the larvae of African catfish
have indicated as not strong in tolerating stresses
highly contrasting their adults.
Acknowledgments
We wish to recognize the Association for Strengthening
Agricultural Research in Eastern and Central Africa
(ASARECA) for sponsoring this study. We also appreciate the
cooperation of TAFIRI staff during the execution of this study.
Authors’ Contributions
GWN and MM together designed the study and had full
cooperation in the writing of this manuscript. GWN cultured
the rotifer, supervised the experiments, analyzed the data, and
prepared a first draft.