International Journal of Marine Science2016, Vol.6, No.31, 1-7
3
Table 2 Mean number of eggs spawned by improved
Oreochromis shiranus
Treatment
Body weight
SL
TL
Eggs
1
40.83±1.18
11.69±.12
14.32±.15
256±7.85
a
2
79.30±1.63
14.93±.13
18.18±.15
436.68±10.25
b
3
132.93±3.32
17.48±.16
21.15±.19
495.38±17.38
c
Means with different superscripts within a column are significantly different (P<0.05)
All the variables (body weight, standard length and total length were not significantly different in this model;
however, high value of relationship was obtained between standard length and eggs (Table3).
Table 3 Multiple regression of weight and length for wild strain of
Oreochromis shiranus
Predictor variable
Beta
p- value
Body weight
-.150
.392
Standard length
.533
.077
Total length
.362
.223
Improved strain of
Oreochromis shiranus
The number of eggs to body weight and length increased as the fish increased in weight and length (Table 2). The
mean minimum number of eggs spawned by improved strain brooders of
Oreochromis shiranus
with mean body
weight ranging from 41g – 133g (12 – 17cm) (all treatments) was 257 and the maximum mean number was 495
eggs. The smallest number of eggs spawned by a brooder weighing 33g (10.9cm) was 115, and the largest number
of eggs was 1083 spawned by a brooder weighing 176g (19.3cm).
Relationship between body weight (BW), standard length (SL) and eggs of improved strain of
Oreochromis
shiranus
The number of eggs, body weight, total length and standard length was significantly correlated with BW (r = 0.74;
P<0.01; n= 180, SL(r = 0.78; P<0.01; n = 180; and TL(r= 0.76; P<0.01; n = 180. The relationship between body
weight and eggs, standard length and eggs was slightly curvilinear but the relationship between standard length
and body weight was linear.
Using the enter method to establish the correlation of the variables, the adjusted R square was 60% and impact of
other variables are indicated in table 4 below,
Table 4 Multiple regression of weight and length for improved strain of
Oreochromis shiranus
Predictor variable
Beta
P -Value
Body weight
-0.052
.772
Standard length
1.112
.001
Total length
.288
.387
Standard length was a significant predictor in this model at P= .001 while the other variables were not significant
predictors. The standardized Beta coefficient gives a measure of the contribution of each variable hence in this case;
a unit change in standard length has a large effect on the dependent variable than the other variables (Table 4).
The number of eggs dropped as shown in figure 1 for wild strain brooders after attaining an average weight of 132g
(18cm), while eggs for improved strain brooders continued to increase with the increase in body weight and length
despite attaining the same weight at which the wild strain brooders showed a remarkable drop in the number of eggs
(Table 5). There were no significant difference between the numbers of eggs produced by improved and wild
strains of
Oreochromis shiranus
at P<0.89.
Table 5 Mean number of egg for wild and improved strain of
Oreochromis shiranus
Treatment
Eggs
Std Error
1
399.39
a
9.80
2
396.29
a
10.44
Means with same superscripts are not significantly different at (P>0.05)
