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African Journal of Environmental Economics and Management ISSN 2375-0707 Vol. 2 (5), pp. 198-206, May, 
2014. Available online at www.internationalscholarsjournals.org © International Scholars Journals 

 

Author(s) retain the copyright of this article. 

 
Full Length Research Paper 
 

An investigation on the diet composition, seasonal 
variation in feeding intensity and ontogenetic dietary 

shifts of L. intermedius in Lake Koka 
   

Godana Bekere1, Kumsa Leqa,2 Wako Ogata2, Zenawi Asfaw Isaias3 
 

1
Biology Department, Addis Ababa University, Addis Ababa, Ethiopia. 

2
Animal and Range Sciences Department, Adama Science and Technology University, Adama and Asella, 

Ethiopia. 
3
Department of Animal Science, Faculty of Agriculture, Admas University College–Addis Ababa. 

 
               Accepted 21 January, 2014 

 

The food and feeding habits of the African big barb LABEOBARBUS INTERMEDIUS (Rüpell, 1836) was studied based 
on 390 gut samples collected in April- May 2011 (dry months) and July- August 2011 (wet months) in Lake Koka, 
Ethiopia. Frequency of occurrence and volumetric methods of analysis were used in this study. Macrophytes, detritus 
and insects were the most important food items occurring in 79.1%, 80.0% and 62.5% of the guts, and accounting for 
46.3%, 27.5% and 18.2% of the total volume of food, respectively. The contributions of phytoplankton, zooplankton, 
fish scales and ostracods were relatively low. Macrophytes and detritus were important food items during the wet 
months occurring in 96.2% and 60.9% of the guts, respectively and comprising 66.1% and 24.0% of the total volume of 
food items, respectively. The contribution of insects was low during the wet months. Detritus, macrophytes and 
insects were found to be the dominant food items in all size classes, whereas the contributions of ostracods, fish 
scales, zooplankton and phytoplankton were low. Based on the results it can be concluded that L. INTERMEDIUS was 
omnivorous in its feeding habits in Lake Koka. 

 
Keywords: L. intermedius, feeding habits, Lake Koka, ontogenetic diet shift. 
 
INTRODUCTION 
 
The African big barb Labeobarbus intermedius (Rüppell, 
1836) is widely distributed in Northern Kenya and in most 
parts of Ethiopia. It is one of the commercially important 
fish species in Ethiopian fisheries (LFDP, 1997; Bjørkli, 
2004; Desta et al., 2006). According to LFDP (1997), the 
annual yield of L. intermedius was about 365 tons per 
year from the inland water bodies of Ethiopia. However, 
recently the consumption of L. intermedius in some rift 
valley lakes (Lakes Hawassa and Koka) declined 
because it was found to be not safe for human 
consumption due to high mercury concentration 
(Mengesha, 2009). 
 
 

 
*Corresponding authors: E-mail: godanabekere@yahoo.com. 

 
 
 
 

The diet composition of fish may vary with in wide ranges 
on temporal and spatial conditions and environmental 
factors (Cabana et al., 1994). According to Persson and 
Crowder (1998), the major factors that influence fish diet 
are fish size, maturity, condition, season (water level), 
bottom, depth, latitude, longitude and habitat types. In 
aquatic systems where the water levels in lakes and 
reservoirs have been known to  

fluctuate, the quality and abundance of food items for 
fish vary significantly through time (Cabana et al., 1994). 
A particular characteristic of fish is that individuals 
increase in size during their ontogeny and this increment 
in size is correlated with changes in food quality and 
quantity in aquatic systems and growth varies according 
to food availability in the environment (Werner, 1988).  
Various authors have studied the food and feeding habits 

 



Godana et al.           198 
 
 

 
of L. intermedius in Ethiopia (Admassu and Dadebo, 
1997; Sibbing, 1998; De Graaf, 2003; Assaminew, 2005; 
Desta et al., 2006; Mengesha, 2009; Deribe et al., 2011). 
Admassu and Dadebo (1997) studied the diet 
composition, length-weight relationship and condition 
factor of L. intermedius in Lake Hawassa and reported 
the diet composition of the species to be phytoplankton, 
insects, detritus, macrophytes, gastropods and fish. 
Desta et al. (2006) have also studied the feeding habits of 
L. intermedius in Lake Hawassa in connection with its 
mercury concentration and have reported the food items 
of the species as gastropods, aquatic insects, 
macrophytes, detritus, fish fry and fish eggs. Sibbing 
(1998) reported that the diet of L. intermedius in Lake 
Tana was composed of benthic invertebrates, mainly 
insect larvae and detritus. According to Assaminew 
(2005), the diet of L. intermedius was composed of 
macrophytes, detritus, insects, nematodes, fish, fish eggs 
and fish scales in Lake Koka.  

Information on the biology and ecology of L. 
intermedius from Lake Koka is scanty. Assaminew 
(2005), Mengesha (2009) and Deribe et al. (2011) have 
studied the diet of L. intermedius in Lake Koka and 
reported the omnivorous feeding habits of the species. 
The type of food items consumed by L. intermedius 
depends on prey availability, season and habitat 
differences and size of the fish (Admassu and Dadebo, 
1997; Sibbing and Nagelkerke, 2001; Desta et al., 2006). 
The available information on the biology and ecology of 
this species from Lake Koka is not sufficient to guide the 
management of the lake. Such area specific information 
is vital for proper management and utilization of the stock. 
The purpose of this study was therefore, to investigate 
the diet composition, seasonal variation in feeding 
intensity and ontogenetic dietary shifts of L. intermedius 
in Lake Koka. 
 
 
MATERIALS AND METHODS 
 
The Study Area 
 
Lake Koka (Latitude: 8

°
19

’ -
 8

°
28

’
 N and Longitude: 39

°
01’ 

- 39
°
09’ E) is located in the northern part of the Main 

Ethiopian Rift (MER) Valley, in the Awash Basin about 
100 km south east of the capital city, Addis Ababa. It is 

located at 1,590 m and has an area of 180 km
2
 (Figure 

1). The region is characterized by a semi-arid to sub-
humid climate (Peder, 2009). The main rainy season 
starts in June and extends to the end of 
August/September, while the short rainy season occurs 
from March to May. The phytoplankton biomass was 

measured to be 5.9 mm
3
 L

-1
 and dominated by 

Microcystis (Mesfin, 1988). The zooplankton was low in 
 

 
 
 

 
diversity but abundant, and there were large populations 
of benthic invertebrates (Peder, 2009). The mean annual 

maximum and minimum temperatures are 30.4
°
 C and 

14
°
 C, respectively as well as the mean depth of 9 m 

(Kibret, 2010).  
The dam is the first hydropower plant in Ethiopia by 

generating electricity for Addis Ababa and other urban 
centers. In addition to electricity generation recently the 
dam is also used for downstream irrigation that is 
accounted for 6,000 ha Wonji Sugarcane Project. The 
area is characterized by a wide and open plain suitable 
for cultivation of agricultural crops. Vegetables are grown 
around the reservoir in the wetland created by the 
receding reservoir water and using diesel water pumps to 
extract the shallow ground water. Sparsely distributed 
Acacia trees are common in the area (Kibret, 2010). Main 
habitats are the surrounding farmland and partly 
protected woodland beside the dam site and hot springs 
below it. Eichhornia crassies has invaded the lake and 
spreading very rapidly (Mesfin, 1988). The main activity in 
the area is farming and the widely grown crop is 
Eragrostis teff. The farmers using the alluvial soil around 
the lake also grow horticultural crops and pulses 
particularly haricot beans (Mesfin, 1988).  

The fishery of Lake Koka is dominated by four fish 
species. These are the Nile tilapia (Oreochromis 
niloticus), the common carp (Cyprinus carpio), the African 
catfish (Clarias gariepinus), and L. intermedius. A tiny 
cyprinodont minnow (Aplocheilichthyes antinorii) also 
exists in the lake. According to the Ethiopian Department 
of Fisheries and Aquaculture, the Lake supports a fishing 
industry of 625 tons of fish each year. The dominant 
species is O. niloticus that contributes about 327 tons per 
year (59% of the total landings) (LFDP, 1997).  

The lake attracts people for work and new settlement to 
develop extensive farming in the catchment. The 
floriculture farms around the Lake release their untreated 
effluents directly to the Lake (Mesfin, 1988). These 
effluents contain fertilizers and pesticides may cause 
pollution and contribute to eutrophication. Recently the 
lake has suffered from severe green algae bloom and 
was referred to as “the green lake” (Peder, 2009). The 
greatest threat to Lake Koka itself is sedimentation and 
recent studies show the rate of sedimentation 25 million 

m
3
 annually. 

 
 
Fish Sample Collection and Measurements 
 
Fish samples of adult L. intermedius were purchased 
from the local fish market. Fishermen in Lake Koka use 
gillnets of 100-160 mm stretched mesh size. Then they 
set their nets late in the afternoon and collect the catch 
early in the morning the following day. In addition to the 

 
 

  



199         Afr. J. Environ. Econ. Manage.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 1: Map of Ethiopia with the relative position of Lake Koka indicated (a) and 
map of Lake Koka with the sampling area indicated 

 

 
adult fish, fingerlings were sampled in the shallow littoral 
area using a beach seine of 6 mm mesh size. Fish 
samples were collected twice during the dry season (April 
and May) and twice during the rainy season (July and 
August). After collection total length (TL) was measured 
to the nearest millimeter and total weight (TW) was 
weighed to the nearest 0.1gram. 
 
 
Gut Content Analysis 
 
We preserved the contents of all non-empty guts in 5% 
formalin solution for further analysis in the laboratory. 
Since L. intermedius is a stomachless fish we sampled 
the content up to the first bend of the intestine. Visual 
examination was used to identify larger food items, but a 
dissecting microscope (LEICA MS5) and a compound 
microscope (LEICA DME) were used to identify 
microscopic food items. In order to investigate the relative 
importance of the different food items, we used the 
following methods of analysis. 
 
 
Frequency Of Occurrence 
 
The number of examined guts in which one or more of a 
given category of food items was found was expressed 
as a percentage of the total number of non-empty guts 
(Windel and Bowen, 1978). This method gives 
information on the proportion of a particular population of 

 
 
fish that fed on that particular food item. 
 
 
Volumetric Analysis 
 
The food items that were found in the guts were 
categorized into different taxonomic groups and the 
volume of each group was measured (Bowen, 1983). 
Then the volume of a given category of food items was 
expressed as a percentage of all the categories of food 
items present in the samples. The importance of different 
food items for different size classes was determined by 
dividing the fish into four size classes (I- < 20.0 cm TL, II-
20.0-29.9 cm TL, III- 30.0-39.9 cm TL and IV- > 40.0 cm 
TL) and determining percentage mean volume of food in 
each size class. 
 
 
RESULTS 
 
Diet Composition 
 
Out of the total number of 266 adult fish samples 
collected 250 (94.0%) were non-empty while the 
remaining 16 (6.0%) were completely empty. The length 
and weight range of the adult fish was 23.3 cm TL to 49.0 
cm TL and 95.4 g to 1,200 g TW. In addition to the adult 
fish, 70 fingerlings collected from the shallow littoral area 
of the lake were included in the gut content analysis. The 
size range of the fingerlings was 5.9 cm to 11.4 cm TL 

 



Godana et al.           200 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Figure 2: The Relative proportions (%) of different food items in the diet of L. intermedius 
using frequency of occurrence and volumetric analysis methods from Lake Koka (MAC-
Macrophytes, DET-Detritus, INS-Insects, PHY-Phytoplankton, OST-Ostracods, SCA-Fish 
scales and ZPK-Zooplankton). 

 
 

Table1: Frequency of occurrence and volumetric contribution of different food items in 
the diet of 320 L. intermedius from Lake Koka. 

 
 Food items Frequency Percent Volume(ml) Percent 
 Phytoplankton 69 21.6 22.9 2.1 
 Blue green Algae 40 12.5 5.0 0.5 
 Green algae 51 15.9 10.0 0.9 
 Diatoms 62 19.3 8.0 0.7 
 Zooplankton 31 9.7 25.4 2.3 
 Rotifers 8 2.5 0.1 0.01 
 Copepods 9 2.7 1.2 0.1 
 Cladocerans 1 0.3 24.1 2.2 
 Insects 200 62.5 198.5 18.2 
 Diptera 155 46.1 135.2 12.4 
 Ephemeroptera 36 11.3 12.3 1.1 
 Coleoptera 49 14.6 32.6 3.0 
 Hemiptera 31 19.2 14.6 1.3 
 Plecoptera 14 4.4 3.7 0.4 
 Detritus 256 80.0 300.3 27.5 
 Macrophytes 253 79.1 506.8 46.3 
 Fish scale 48 15.0 21.8 2.0 
 Ostracods 61 19.1 17.9 1.6 

 
 

 
and 1.6 g to 12.4 g TW. All the fingerlings were non-
empty.  

The food items identified from the gut contents of L. 
intermedius were macrophytes, detritus, insects, 
phytoplankton, zooplankton, ostracods and fish scales 
 

 
 

 
(Figure 2, Table 1). From these food items macrophytes, 
detritus and insects occurred in high number of guts and 
constituted the bulk (92.0%) of the food consumed by 
volume (Figure 2, Table 1). The remaining food items 
accounted for only 8.0% of the total volume of food items. 

 
 

  



201         Afr. J. Environ. Econ. Manage. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 3: The relative proportion (%) of different food items in the diet 
of L. intermedius during dry month (a) and wet month (b) from Lake 
Koka (DET-Detritus, MAC-Macrophytes, INS-Insects, PHY-
Phytoplankton, OST-Ostracods, SCA-Fish scales and ZPK-
Zooplankton). 

 
 
Macrophytes were the most important food items 
occurring in 79.1% of the guts and constituting 46.3% of 
the total volume of food items (Figure 2, Table 1). Detritus 
occurred in 80.0% of the guts and accounted for Diptera 
were by far the most important groups occurring in 46.1% 
of the guts and constituting 12.4% of the total volume 
(Table 1). The contribution of other groups of insects was 
low (Table 1).  

The frequency of occurrence of phytoplankton was 
relatively high (21.6%) but their total volumetric 
contribution was rather low (2.1%). Blue green algae, 
green algae and diatoms were encountered during the 
present study, among which green algae had the highest 
contribution (Table 1). Zooplankton occurred in 9.7% of 
the guts and accounted for 2.3% of the total volume of 
food consumed (Figure 2, Table 1). Fish scales occurred 
in 15.0% of the guts and accounted for 2.0% of the total 

 
 
27.5% of the total volume of food items (Figure 2, Table 
1). Insects occurred in 62.5% of the guts and their 
volumetric contribution was 18.2% of the total volume of 
food items (Figure 2, Table 1). Among the insect groups, 
volume (Figure 2, Table 1). Ostracods occurred in 19.1% 
of the guts and constituted 1.6% of the total volume 
(Figure 2, Table 1). 
 
 
Seasonal Variation In The Diet Of L. INTERMEDIUS 
 
There was notable variation in the type of diet and the 
proportions consumed by L. intermedius in Lake Koka 
during the dry and wet months. Generally, the number of 
food items consumed during the dry month was much 
higher (seven) than the number of food items consumed 
during the wet month (three) (Figure 3a, b). 

 



Godana et al.           202 
 
 

 
Table 2: Frequency of occurrence and volumetric contribution of different food items in the diet of 320 L. intermedius 
during dry and wet months from Lake Koka. 

 
  Frequency Occurrence (%) Volumetric Contribution (%) 
 Food items Dry Months Wet Months Dry Months Wet Months 
 Phytoplankton 42.1 - 5.7 - 
 Blue green algae 24.4 - 1.2 - 
 Green algae 31.1 - 2.5 - 
 Diatom 37.8 - 2.0 - 
 Zooplankton 17.1 - 6.1 - 
 Rotifers 2.4 - 0.02 - 
 Copepods 5.5 - 0.3 - 
 Cladocerans 15.4 - 5.8 - 
 Ostracods 37.2 - 4.4 - 
 Insects 81.7 41.0 32.5 9.8 
 Diptera 76.2 19.2 25.4 4.7 
 Hemiptera 18.9 - 3.6 - 
 Ephemeroptera 20.7 1.3 2.5 0.4 
 Coleoptera 0.6 30.8 0.2 4.7 
 Plecoptera 7.9 0.6 0.7 0.1 
 Detritus 98.8 60.9 34.0 24.0 
 Macrophytes 62.8 96.2 12.7 66.1 
 Fish scales 24.4 - 4.6 - 

 

 
Detritus was the most important food item during the dry 
month. It occurred in 98.8% of the stomachs and 
volumetrically its contribution was 34.0% of the total 
volume of food items (Figure 3a, Table 2). Insects 
occurred in 81.7% of the stomachs and accounted for 
32.5% of the total volume food consumed (Figure 3a, 
Table 2). Diptera were the most important food items 
among the insect groups. They occurred in 76.2% of the 
stomachs and constituted 25.4% of the total volume of 
food items (Figure 3a, Table 2). The contribution of other 
groups of insects was low because of their low frequency 
and volumetric contributions (Figure 3a, Table 2). 
Macrophytes and phytoplankton occurred in 62.8% and 
42.1% of the stomachs, respectively and comprised 
12.7% and 5.8% of the total volume food items, 
respectively. Ostracods, fish scales and zooplankton 
occurred in 37.2%, 24.4% and 17.1% of the stomachs, 
respectively. Their volumetric contributions were 4.4%, 
4.6% and 6.1% of the total volume of food items, 
respectively (Figure 3a, Table 2).  

During the wet month, macrophytes were the most 
important food items occurring in 96.2% of the guts and 
accounting for 66.1% of the total volume food items 
(Figure 3b, Table 2). Detritus occurred in 60.9% of the 
guts and comprised 24.0% of the total volume food 
consumed (Figure 3b, Table 2). The contribution of 
insects was relatively low. They occurred in 41.0% of the 
guts and constituted 9.8% of the total volume of food 
items (Figure 3b, Table 2). During the wet month the 
contributions of foods of plant origin was very high while 
the contributions of animal prey was low. 

 
 
Ontogenetic Dietary Shift 
 
Percent mean volume contribution of different food items 
with size of fish is given in (Figure 4). Detritus, 
macrophytes and insects were the dominant food items in 
all size classes, whereas the contribution of ostracods, 
fish scales, zooplankton and phytoplankton was low 
(Figure 4). In size class < 20.0 cm TL the dominant food 
items were detritus 39.7% followed by insects 36.3% 
(Figure 4). The contributions of macrophytes and 
zooplankton were 10.0% and 6.1%, respectively of the 
total volume of food items. The contributions of 
ostracods, fish scales and phytoplankton were 3.3%, 
1.4% and 3.1% of the total volume of food items, 
respectively (Figure 4). In this size class, the most 
important food items were detritus and insects. These two 
food items constituted 76.0% of the total volume of food 
consumed (Figure 4). The remaining food items 
constituted 24% of the total volume of food items (Figure 
4).  

In size class 20.0-29.9 cm TL macrophytes, detritus 
and insects were important food items accounting for 
45.0%, 34.7% and 12.8% of the total volume of food 
items, respectively (Figure 4). These three food items 
constituted 92.5% of the total volume of food items within 
that size class (Figure 4). The less important food items 
namely, ostracods 0.9%, fish scales 2.8%, zooplankton 
1.0%, and phytoplankton 2.8% collectively constituted 
less than 10% of the volume of food consumed within the 
size class (Figure 4).  

The dominant food items in size class 30.0-39.9 cm TL 
 



 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 4: The relative proportion (%) of different prey items in the diet of L. intermedius at 
different size classes from Lake Koka (DET-Detritus, MAC-Macrophytes, INS-Insects, OST, 
Ostracods, SCA-Fish scales, ZPK-Zooplankton and PHY-Phytoplankton). 

 

 
were macrophytes 48.6%, detritus 25.8%, and insects 
19.6% and these three food items constituted 94% of the 
total volume of food items within the size class. The 
contributions of ostracods 1.5%, fish scales 1.4%, 
zooplankton 0.8% and phytoplankton 2.2% were 
relatively low, collectively constituted only 6% of the total 
volume of food consumed in that size class (Figure 4).  

In size class >40 cm TL the order of the importance of 
dominant food items was similar. Macrophytes, detritus 
and insects constituted the bulk of the food items 
consumed. These food items accounted for 45.0%, 
33.0% and 12%, respectively of the total volume of food 
items consumed within the size class (Figure 4). The less 
important food items were again ostracods 2.7%, fish 
scales 4.0%, zooplankton 0.3% and phytoplankton 2.9%. 
The dominant food items constituted about 90% of the 
total volume of food items while the minor food items 
constituted only about 10% of the total volume of food 
items within the size class (Figure 4). 
 
 
DISCUSSION 
 
L. intermedius fed mainly on detritus, macrophytes and 
insects in Lake Koka. Unlike the present study, the major 
food items of L. intermedius were mollusks, fish prey and 

 

 
aquatic insects in Lake Hawassa (Desta et al., 2006). 
Comparable with the present study the main food items of 
L. intermedius constituted macrophytes, detritus and 
aquatic insects in Lake Koka (Assaminew, 2005). 
Similarily, in Lake Tana the diet of L. intermedius was 
dominated by benthic prey organisms especially insect 
larvae and detritus (Sibbing, 1998; De Graaf, 2003). Diet 
studies of big barbs from other inland waters of Africa and 
Asia have been shown to be omnivorous and the fish is 
able to change its diet depending on availability of prey, 
seasonal and spatial differences (Admasu and Dadebo, 
1997; Sibbing and Nagelkerke, 2001).  

The high occurrence and volumetric contribution of 
detritus in guts of L. intermedius showed the significant 
contribution of this food item in their nutrition. Detritus is 
reported as a dominant food item of B. bocagei, B. 
staeindachneri and B. cyclolepis and additional food for  
B. comiza in Maritza River from Bulgaria (Losos et al., 
1980). Dietary studies on big barbs in different lakes 
showed that (Corbet, 1961; Cambray, 1983; Admassu 
and Dadebo, 1997) the ingestion of detritus, sand 
particles and benthic food items indicated the ability of 
the species to possess benthic habitats. Detritus is 
considered low in nutritional value (Bagenal and Braum, 
1978; Bowen, 1979). Several studies in lotic and lentic 
water systems have considered that an increased 

 

  
203         Afr. J. Environ. Econ. Manage. 



Godana et al.           204 
 
 

 
consumption of detritus is a prime response to a decline 
of higher value primary food resources (Bowen, 1979; 
King et al., 2003).  

The importance of insects mainly Dipterans in the diet 
of different Barbus species was reported by various 
authors (Hyslop, 1980; Losos et al., 1980; Piet, 1998). 
This was probably due to the dense stand of aquatic 
weeds that support significant biofilm assemblage of 
benthic prey production noted by Piet (1998). Nagelkerke 
and Sibbing (1993) reported the importance of 
macrophytes in the diets of B. sukris and B. truttiformis in 
Lake Tana, Ethiopia. The results of the present study are 
in agreement with the findings of other investigators in 
different water bodies of Africa where macrophytes, 
detritus and insects dominate the gut content of the 
species. Unlike the present study, Desta (2006) reported 
the dominance of gastropods in the diet of B. intermedius 
in Lake Hawassa the volumetric contributions of 
zooplankton, phytoplankton, ostracods and fish scales 
were relatively low in the diet of L. intermedius. These 
food items could probably be consumed accidentally 
when the fish searches other food items in the 
environment. According to Losos et al. (1980) mollusks, 
beetles larvae and ants were incidentally consumed in 
the diet of B. cyclolepis because of their low volumetric 
contributions in Maritza River, Bulgaria. In many tropical 
freshwater ecosystems zooplanktivorous fishes were 
poorly distributed (Piet, 1998). De Graaf (2003) 
documented three zooplanktivorous barbs, two small 
barbs (B. tanapelagius and B. humalis) and one big barb 
B. brevicephalus in Lake Tana. Zoopanktivory and the 
filter feeding habits on zooplankton are rare in tropical 
waters (De Graaf, 2003).  

Piscivory was not observed in the diet of L. intermedius 
during the present study. This is probably due to the 
presence of a top predator, C. gariepinus which feeds on 
C. carpio, O. niloticus, Barbus sp.  
Piscivory is not common in Cyprinids due to the absence 
of oral teeth and the shortage of stomach acidity (Sibbing, 
1982; Desta et al., 2006). However, piscivory is relatively 
common among the African cyprinids due to the presence 
of sufficient fish prey and the absence of other 
piscivorous fishes while in Europe some cyprinids 
specialized on fish even in the presence other piscivorous 
fish (Desta et al., 2006). Nagelkerke (1997) noted that in 
Lake Tana, Ethiopia five out of eight big barbs found to 
be specialized on fish and the nature of piscivory is due 
to the abundance of B. humilis in the littoral region and B. 
tanapelagius in the pelagic area. High level of piscivory 
was observed in the diet of B. intermedius in Lake 
Hawassa, Ethiopia (Admassu and Dadebo, 1997; Desta 
et al., 2006).  

Seasonal variation was observed on the type of food 
and their proportion during the dry and wet periods of the 
 

 
 
 

 
Year detritus and insects were the most important food 
items during the dry period. Detritus was probably 
ingested with insects when the fish was trying to pick 
insects from the sediment assisted by their ventral mouth 
projection that is suited for benthic feeding (Adeyemi, 
2009). During the wet period of the year, macrophytes 
and detritus were the most important food items. The 
source of detritus could be probably floods that 
introduced fragments of plant materials in the lake. 
Balcombe et al. (2004) suggested that Barbus sp. 
consumed more detritus and fewer insects during high 
water level in a Sri Lankan reservoir. High water levels 
designated as resource rich while low water levels have 
poor resources in trophic dynamics in lentic systems 
(Balcombe et al., 2004). The availability of food items 
changes throughout the year in tropical region due to 
seasonal changes and feeding habits of fish depend on 
seasonal variation (Desta et al., 2006; Peder, 2009).  

Fingerlings mostly fed on detritus and insects in large 
amounts while in larger size classes macrophytes, 
detritus and insects were the most dominant food items. 
The remaining food items were of minor contribution in 
the diet of L. intermedius. An attempt was made to 
determine ontogenetic diet shift. There was slight 
ontogenetic variation in the diet of L. intermedius among 
the different size classes. The importance of 
macrophytes, detritus and insects was dominant in all 
size classes while the contributions of ostracods, 
phytoplankton, zooplankton and fish scales were low 
regardless of their size. The slight variation observed was 
that macrophytes were relatively unimportant in the diet 
of the smallest size class while they are dominant food 
items in larger size classes. Moreover, insects that were 
dominant in the smallest size class were relatively 
unimportant in larger size classes. Desta et al. (2006) 
studied the feeding habits of L. intermedius in Lake 
Hawassa and reported slight ontogenetic diet shift in L. 
intermedius from Lake Hawassa. They noted that insects 
were important food source for juvenile, but their 
importance declined with size of fish. The results of the present 
study agree well with the report of Desta et al. (2006). Desta et 
al. (2006) also reported that L. intermedius in Lake Hawassa 
shifted to piscivorous feeding habits as its size increases. 
However no fish prey was encountered in the present study. 
Corbet (1961) studying B. altianalis in Lake Victoria and Spataru 
and Gophen (1987) working on B. altianalis in Lake Kinneret, 
(Israel) pointed out lack of ontogenetic diet shift and therefore, 
small and large sized fish consumed similar food items. 
 
 
 
CONCLUSION 
 
The most important food items of L. intermedius in Lake 
Koka were detritus, macrophytes and insects while 



205         Afr. J. Environ. Econ. Manage. 
 

 

 
zooplankton, fish scales, phytoplankton and ostracods 
were low in their contribution. During the dry period the 
food items that were identified in the diet of L. intermedius 
were detritus, insects, macrophytes, zooplankton, fish 
scales, phytoplankton and ostracods. Among these food 
items detritus, insects and macrophytes were the most 
important food items while the remaining food items were 
low in their contribution. During the wet period only three 
food items were identified. These were macrophytes, 
detritus and insects and all were important in the diet of L. 
intermedius. The dominant food items in all size classes 
were detritus, macrophytes and insects while the 
remaining food items were low in their contribution. 
Detritus and insects were the dominant food items of 
juveniles, while macrophytes, detritus and insects were 
the dominant food sources of adults. Generally, L. 
intermedius was found to be omnivorous in its feeding 
habits; macrophytes become more important in its diet as 
it grows older. 
 
 
ACKNOWLEDGEMENTS 
 
We thank fishermen Kecha Fiche and Abu Geleta for 
their assistance during the fieldwork. Yirgashewa Bekele 
is acknowledged for assisting us during the laboratory 
work. Thanks are also due to Dr. Andargachew Gedebo, 
the NORAD Project coordinator, for providing a vehicle 
for the field trips. Biology Department of Hawassa 
University provided us the necessary facilities and 
laboratory space. Ethiopian Ministry of Education 
provided financial assistance for the second author. 
 
 
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