International Journal of Aquaculture, 2018, Vol.8, No.1, 1-7
4
Table 1 Mean of character size and the asymmetry indexes of
H. vittatus
(1),
H. brevis
(2) and
H. forskalii
(3)
Character
Character size (R+L)/2
Asymmetry index (R-L/R)%
Fish 1
Fish 2
Fish 3
Fish 1
Fish 2
Fish 3
HL
6.5
6.3
6.5
0.6
0.6
0.6
ED
2.1
2
2.2
0.4
2.4
0.9
POL
3.4
3.3
3.8
0.6
4.5
0.8
SNL
2.8
2.6
2.9
10.7
9.5
5.8
PFL
1.8
1.8
1.9
2.7
0
1.1
VFL
1.7
1.6
1.8
1
2.5
5.7
PVFL
14.7
11.7
13
0.1
0.2
0.4
PSL
4.6
4.3
4.6
0.2
1.9
1.2
CPL
3
2.9
3.2
1.2
1.8
0.6
PFR
14.1
13.45
12.05
4.4
0.8
2.5
LLS
57.1
55.6
54.3
2.1
2.2
1.7
DLS
9.8
10.5
11.3
3.8
5.5
4.1
VLS
6.5
5.7
6.2
7.8
4.3
0.3
GR
55.4
54.9
56.6
2.5
0.8
0.8
Mean
24.5
23.6
24.1
5.1
4.9
3.5
4 Discussion
In this study significant difference in the degree of FA among the populations of the three species was detected.
Occurrence of FA in a single individual may prove meaningful biologically in identifying environmental stressors
within the Nile water. The Different degrees of FA among individuals of fish in each population may identify
environmental instability. Individual specimens sampled could have experienced different developmental
conditions during their development. Differences in the percentage of FA may be attributed to the ability of the
traits to buffer developmental alterations (Lens et al., 2002). Therefore, environmental condition takes part for the
overall condition of the species and may enhance its fitness to resist alterations. According to Allan (2004),
Richards et al. (1996) and Roy et al. (2003), human activities along the Nile can have some impacts on water
quality, habitat, and aquatic biota and can play a significant role in defining Nile condition and thus create
developmental stressors resulting in FA. In addition, pesticides and fertilizers are main factors to contamination of
water and aquatic natural resources (Manjare et al., 2010). However, water chemistry may have a more direct
influence on FA and may be a more powerful predictor of developmental stress. Other factors such as nutrition,
chemical contaminants and pH have also been shown to increase FA (Allenbach, 2011). Annual variability in
temperature and water levels could also impact a variety of stressors contributing to increase variability among
individuals. Many studies have shown FA to be a reliable bio-indicator of environmental stress (Hardersen, 2000;
Seixas et al., 2016).
Since, asymmetry in the morphology of fish specimens was observed, it might be a sign that fishes in the
sampling area underneath environmental disturbances. Observed fluctuating asymmetry would be an indication of
existing pollutants within the fish habitat which consequently affected its morphology. The continuity of the fishes
in the polluted and disturbed environment will likely affect fish morphology and cause asymmetry. The present
data shows the indication for FA of the fishes that can be a result of a stressed environment probably from
different types of aquatic pollutants. The polluted ecosystem will eventually cause morphological variation as
these effluents interfere during its growth and development (Bonada and Williams, 2002).
Many Studies showed that greater fluctuating asymmetry is the outcome of the species towards environmental
situation (Ducos and Tubago, 2015). Other studies have also showed direct relationship between environmental
stress and the increase of abnormalities (Taylor, 2001; Lemly, 2002; Hermita et al., 2013; Lutterschmidt et al.,
