International Journal of Aquaculture, 2017, Vol.7, No.20, 126-133
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2.4 Stomach content analysis
A total of 408 gut samples were examined for food composition. The numbers of specimens examined were
V.
beso
136,
G. chebera
156 and
G. quadrimaculata
116. Out of these 38 (9.31%) of the fishes were found with
empty stomachs. The food items recorded were diverse groups of phytoplankton, zooplankton, Annelids, detritus
and sandy grains (Table 5). The zooplankton such as copepods and cladocera and oligochaete worms were noticed.
In addition detritus and sandy grains formed important constituents in the stomach content of the fishes.
Table 5 Frequency of occurrence of food items in the gut content of fishes
Food item
Varicorhinus beso
Garra chebera
Garra quadrimaculata
(%)
(%)
(%)
Chlorophyceae
31.15
25.69
28.8
Cyanophyceae
10.65
13.1
16.34
Bacillariophyceae
87.70
89.58
87.5
Zooplankton
27.86
18.05
15.38
Detritus
100
100
100
Annelids
10.65
5.55
1.92
Sand grain
100
100
100
All the stomachs of
V. beso
showed the presence of detritus and sand grains (100%) followed by diatoms with
87.70%.
Chlorophyceae
(green algae) were found in 31.15% fish stomachs. Zooplankton was collected from
27.86% of the stomachs followed by
Cyanophyceae
and
Oligochaeta
in 10.65% of examined stomachs (Table 6).
The food items in the stomachs of
G. chebera
were detritus and sand grains (100%) diatoms (89.58%),
Chlorophyceae
(25.69%), Zooplankton (18.05%) and
Cyanophyceae
(13.1%) and Annelids (5.55%) of fishes.
Detritus and sandy grains formed the bulk of the ingested item in all the stomachs (100%) of
G. quadrimaculata
.
Diatoms were found in 87.5% of the examined fish, followed by
Chlorophyceae
28.8% and
Cyanophyceae
16.34%. Zooplankton were observed in (15.38%) of stomachs examined fishes.
Table 6 Numerical abundance of food items in the stomach contents
Food item
Varicorhinus beso
Garra chebera
Garra quadrimaculata
Number
%
Number
%
Number
%
Chlorophyceae
1205
19.27
1054
15.64
1251
16.69
Cyanophyceae
522
7.38
488
7.24
479
7.23
Bacillariophyceae
5382
72.69
5122
76.02
4720
74.56
Zooplankton
75
0.60
55
0.77
39
1.04
Annelids
34
0.062
19
0.28
4
0.47
Total
7218
100
6738
100
6493
100
Numerically, Bacillariophyceae was the most important food item in the stomach of the fishes examined (Table 6)
followed by green and blue-green algae. Zooplankton and oligochaete worms were also found occasionally
constituted 1.04 and 0.47% of the diet.
Analysis of stomach contents is a method for determining the food and feeding habits of fishes by which we can
easily find what the fish take as food. Palmores et al. (1997) stated that stomach content results would help to
reduce intra and inter specific competition for ecological niche and in providing straight forward models of
stomach content dynamics. In the present study, over 90.69% of the fish specimens showed food in the stomach.
The results indicated that river bed is composed of high number of decomposed material and mixed with
periphyton composed of large number of diatoms and green algae. The stomach content showed the presence of
large amount of sand grains and partially decomposed animal and plant tissues (detritus) suggesting their bottom
feeding habit (Ayotunde et al., 2007; Ayoade, 2011). Admassu and Dadebo (1997) and Zerihun et al. (2006)
found that L. intermedius in Lake Hawassa feeds on phytoplankton, insects, detritus, macrophytes, gastropods and
fish. According to Assaminew (2005), the diet of
L. intermedius
was composed of macrophytes, detritus, insects,
