International Journal of Aquaculture, 2017, Vol.7, No.16, 106-110
107
Subsequently the fish farmer gets very little or no profit as a result. Various strategies have been devised to
control breeding of tilapia and increase its body size, among which is all male tilapia production which eliminates
reproduction and result to faster growth (Guerrero, 1985).
The Scientist report has shown that male tilapia had better growth than the female. The superiority of the
performance of male tilapia over the female goes beyond just genetic capability (Muhammad et al., 2008). Also,
the breeding pattern of females which involve incubation of eggs in the mouth during spawning greatly prevent
active feeding, hence lead to reduced growth (Muhammad et al., 2008). The propagation of all male tilapia
however is fast becoming popular in most part of the world as it removes the prolific breeding characteristics
associated with tilapia production and enhances faster growth to table size. This study was designed to investigate
the performance of all male and mixed sex tilapia reared in an outdoor system.
2 Material and Methods
This study was conducted at the Department of Fisheries and Aquaculture, University of Agriculture Makurdi,
Benue State, Nigeria. Hatchlings of Nile tilapia were collected from the mouth of females maintained in outdoor
earthen pond at the Fisheries Research Farm. Half of the hatchlings were move indoor for hormonal
administration following the methods described by Olufeagba and Okomoda (2015). Fish for sex reversal were
maintained in a well aerated 60 x 30 x 30 cm
3
glass aquaria tanks. One hundred grammes (100 g) of coppens
®
powdered feed were mixed with 30 μg of 17 α-methyltestosterone (Sigma E-4876) (already dissolved in 95%
ethanol). This was mixed in a plastic bowl and oven-dried at 65°C for one hour. The prepared feed was fed for
twenty-eight days before the commencement of this study. Triplicate batches each of fifty hormonal sex reversed
and fifty mixed sex tilapia fingerlings were transferred into six outdoor rearing tanks where they were fed with
coppens
®
commercial diet (45% CP) for twenty-four weeks. Water quality parameters such as temperature,
conductivity, total dissolved solids and pH were monitored fortnightly using a digital multi-parameter water
checker kit (Hanna water tester, Model HL 98126, Made in Romenia). Fish were fed twice daily (08:00 am and
06:00 pm) at 5% body weight. The fish were weighed weekly to determine new weight gain and adjust rations
based on the new body weight gain. Growth performance and nutrient utilization were assessed at the end of the
experiment using the equations below.
(a) Mean Initial Weight (MIW) =
Roma o ma t o Rt t浔a ੪
Roma
ݐ
t浔 Rt t浔a ੪
(b) Mean Weight Gain (MWG) =
tm t ma t o 䘥 tm o ma t o
(c) Growth Rate =
tm t ma t o䘥 tm o ma t o tt
浔mo R Rt o t ㌳䁏t浔 to
(d) Specific Growth Rate (%/day) =
aR
t
o 䘥 aR
t
o
o 䘥o
Where Wt
1
= Initial weight
Wt
2
= Final weight
T
2
-T
1
= Duration (in days) considered between Wt
2
and Wt
1
(e) Feed Fed (FF) =
Rt Roma ttt om t 䁏t浔 tt
ݐ
t浔 Rt t ੪
(f) Feed Conversion Ratio (FCR) =
浔o ttt om t
to t o m
(g) Feed Efficiency Ratio (FER) =
to t o m tt
浔o ttt om t
(h) Protein Efficiency Ratio =
to t o m
䁏浔Rot tt
Where Protein Fed =
protein in diet total diet consumed
tt
