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Email: drpnatarajan123@gmail.com;Phone: +251-969-454307

East Afr. J. Biophys. Comput. Sci., Vol. 2, Issue. 1 

S. David Kingston1, Koos Vijverber2, P. Natarajan*3 and Tigist Ashagre Amare3

1Department of Aquatic Biology and Fisheries, University of Kerala, Trivandrum, India, 
2 Centre for Limnology, Netherlands Institute of Ecology, Niewersluis, Rijsstraatweg, The Netherlands
3 Department of Aquatic Sciences, Fisheries and Aquaculture, Hawassa University, Hawassa, Ethiopia 

KEYWORDS: 
Feeding habit;  

Vamanapuram River; 

ABSTRACT 
An understanding of the feeding habits of fish species in natural environment gives clues 
for selecting the species for aquaculture. It helps in formulating artificial feeds for 
culturing species under artificial conditions for small scale or large scale aquaculture. The 
main objective of the present study was to find the food preferences of fish species in 
different ecological niches such as low land streams, riverine and estuary. Stomachs were 
cut, food items removed and stored in 4% formalin. Diet breadth was calculated as per the 
standard methods widely recommended. The diet breadth calculated for the fish 
assemblages in Vamanapuram River showed that Puntius amphibius has the highest 
breadth of 6.64. The surface feeding fishes had low diet breadth which ranged from 1.13-
1.83. Their main food has been observed to be terrestrial insects. The generalists like 
Rasbora daniconius and Puntius filamentosus have diet breadth of 3.27 and 4.15, 
respectively. Whereas fish species found in  estuarine habitats showed diet breadth range 
from 1.00 to 2.82. The fishes present in the upper regions of the river habitat were 
observed to have low diet breadth than lowland streams. In general, high diet breadth 
values were observed during February to May. The breadth of Barilius bakeri showed 
minor variations among the three seasons (1.00 to 1.20). Based on the diet breadth, the 
majority of the fishes in Vamanapuram River generalists..  

INTRODUCTION 

The diet breadth of fish species in a community 
explains the spectrum or range of food items 
consumed by the fishes. The variations in diet 
breadth can be used to classify the fishes as 
specialist and generalist (Saswata Maitr et al., 
2019). High breadth shows a generalistic mode 
of feeding and low values indicate more 

specialistic nature. In riverine ecosystems, 
because of the dynamic nature, and with varied 
habitats the fishes have adaptations to feed on 
variety of food items. Several studies pertaining 
to the diet breadth of fish species of different 
Indian rivers and streams have been carried out 
(Arunachalam et al., 1988; Arun, 1992; David 
kingston, 1992; David Kingston et al., 2011). 
The diet breadth of Srilankan streams, studied 

East African Journal of Biophysical and Computational Sciences 

Journal homepage : https://journals.hu.edu.et/hu-journals/index.php/eajbcs 
Hawassa University

College of Natural & Computational Sciences

Year 2021

Volume xx No xx

27

Diet breadth of fish communities in Vamanapuram river, Kerala, South India 

Fishes; 

Research article

mailto:drpnatarajan123@gmail.com


East Afr. J. Biophys. Comput. Sci., Vol. 2, Issue 1 
 

by Moyle and Senanayake (1984) showed that 
most of the species had narrow diet breadths. 
Julio Cesar Sa- Oliveira et al. (2014) studied 
diet and niche breadth and overlap in fish 
communities within the area affected by an 
Amazonian Reservoir in Brazil. Heng et al. 
(2018) reported the diet breadth and dietary 
overlap between three commercially important 
food fishes of Cambodia. In the present study, 
the diet breadths of different fish species from 
the riverine stretches of Vamanapuram River, 
South Kerala,  India have been studied in detail. 

MATERIALS AND METHOD 

Vamanapuram River is one of the major rivers 
in Kerala with a catchment area of 787 square 
kilometre located in Thiruvananthapuram and 
Kollam districts of Kerala state, India. It is 
found at latitude of 8 ̊ 35’ 24’’ N and 8 ̊ 49’ 13’’ 
N and longitude of 76 ̊44’ 24’’ E and 77 ̊12’ 
45’’ E.  The area is characterized by lateritic 
uplands with intermittent valleys. The altitude 
ranged from 40m to 300m. It originates from 
Ponmudi Hills (1074 m above sea level) flows 
onwards through Vamanpuram Town, and joins 
the Kadinamkulam backwater and then enters to 
the Arabian Sea at Mudalapallipozhi near 
Perumathura, 25 km north of 
Thiruvananthapuram city. The climate is 
typically sub-equatorial with three main seasons, 
the premonsoon (February- May), monsoon (June 
- September) and postmonsoon (October - 
January). The premonsoon and later part of the 
post-monsoon periods are usually dry (Pisharody, 
1987).  

Twelve sites were chosen for sampling 
throughout the Vamanapuram River from the 
lowlands to mouth of the river. The study sites 
were selected in different habitats like lowland 

streams (Habitat I), riverine (Habitat II) and 
estuary (Habitat III). Among the 12 study sites, 
seven were lowland streams three riverine and 
two estuarine stations. For trophic estimates, 
fishes were collected using monofilament gill 
nets. Depending on the habitats, depth of water 
column and availability of fishes, gill nets of 
varying mesh sizes were used. A uniform effort 
of 20 minutes was set for all the nets at all 
habitats during 10 am in the morning. Soon after 
the net is hauled, fishes were removed and 
anaesthetized in 50ppm Benzococaine to prevent 
the regurgitation of food particles. Then the fishes 
were transferred to 4% formalin for preservation. 
Large sized fishes were injected with formalin 
using a hypodermic syringe and then preserved in 
4% formalin.  

Thirty two (32) fish species representing 17 
genera were collected during the study period. 
Dietary analysis was done on each individual fish. 
The fish were cut open and guts removed. The 
contents of the stomach or intestine up to the first 
bend and if no stomach was present the gut was 
pressed in a gridded glass slide and examined 
using dissection microscope. The minute and 
microscopic items were observed in high power 
microscopes. The diet breadth was calculated 
using the formula of Levins (1968): 

  B = 1 / Pij, 

where Pij is the proportion of the food in each 
category. 

RESULTS AND DISCUSSION 

Thirty two (32) fish  species representing 17 
genera were collected during the study period 
(Table 1). Among the 32 species available in the 
Vamanapuram river, Puntius amphibious (PA) 

28



East Afr. J. Biophys. Comput. Sci., Vol. 2, Issue 1 
 

showed the highest diet breadth of 6.64 (Table 1). 
This species was observed to be a bottom feeder 
and it had affinity for a wide range of food items. 
Another bottom feeder, Garra mullya (GM) had 
a diet breadth of 2.21, whose main food items 
were small algae and filamentous algae. The 
morphological adaptation of this species 
especially mouth structure was more suited for 
the bottom feeding nature. Other bottom feeding 
fishes like Etroplus maculatus (EM), Mystus 
montanus (MM), Puntius melanampyx (PM), 
Mystus armatus (MA), Puntius ticto (PT) and 
Puntius vittatus (PV) had diet breadths ranged 
from 2.78 - 5.31. Of all the bottom feeding fishes 
Garra mullya (GM), Puntius ticto (PT) and 
Puntius vittatus (PV) came under category one in 
which their diet breadths was more or less in the 
same vicinity. The surface feeding fishes like 
Danio aequipinnatus (DA), Barilius bakeri 
(BB) and Aplocheilus lineatus (AL) had diet 
breadths of 1.83, 1.18 and 1.13 respectively, and 
they relied more on terrestrial insects as their 
main food. The generalists fish groups such as 
Rasbora daniconius (RD) and Puntius 
filamentosus (PF) had diet breadths of 3.27 and 
4.15 respectively. The estuarine fishes had diet 
breadth values ranged from 1.00 - 2.82.  Out of 
these, 42.5% had low diet breadth values (< 2.00). 

In general, the riverine habitat had low diet 
breadths than lowland stream habitats. PA 
showed highest breadth in Habitat-I (6.68) 
followed by Mystus montanus (MM) (5.31) and 
Puntius melanampyx (PM) (5.14). The surface 
feeders Danio aequipinnatus (DA), Barilius 
bakeri (BB) and Aplocheilus lineatus (AL) had 
diet breadths of 2.08, 1.20 and 1.13 respectively. 
While comparing the breadth values of Habitat-I 
and Habitat- II, with the exception of Puntius 
ticto (PT) (3.59) and Labeo dero (LD) (1.58), all 

other species in the riverine habitat had low 
breadth values than lowland stream habitat. In the 
estuarine habitat, diet breadth values were very 
low (1.00 - 2.42) indicating the dominance of 
specialists.  

The fish assemblages of Vamanapuram River had 
wide temporal variations in diet breadth (Figure 
1). In general, high breadth values were observed 
during premonsoon season. The breadth of 
Puntius amphibious (PA) during premonsoon 
was 6.28, whereas 4.17 during postmonsoon. The 
increased number of diet breadth was due to the 
concentration of food materials in place due to 
reduced water flow during premonsoon months.  
In species like DA, BB, PS and AL, the breadth 
values had an increase during monsoon and there 
was further a reduction during postmonsoon due 
to increased water flow during monsoon months 
and reduction of water flow during post monsoon 
months. 

 

 

 

 

 

 

 

 

 

 

 

 

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East Afr. J. Biophys. Comput. Sci., Vol. 2, Issue 1 
 

Table -1. Diet breadth of fish species in Vamanapuram River (mean count ) 

Species Habitat I 
 

Habitat II  Habitat III  Overall Diet 
breadth 

Puntius amphibious (PA) 6.68 5.80  6.64 
Puntius filamentosus (PF) 4.14 3.87  4.15 
Danio aequipinnatus (DA) 2.08 1.28  1.83 
Rasbora daniconius (RD) 3.33 2.06  3.27 

Puntius ticto (PT) 3.52 3.59  3.41 
Puntius vittatus (PV) 2.78   2.78 

Puntius melanampyx (PM) 5.14   5.14 
Garra mullya (GM) 2.44 2.00  2.21 
Puntius sarana (PS) 2.54   2.54 
Barilius bakeri (BB) 1.20 1.02  1.18 

Etroplus maculatus (EM) 4.36 2.44 1.00 4.29 
Mystus armatus (MA) 4.83   4.83 

Mystus montanus (MM) 5.31   5.31 
Amblypharyngodon microlepis (AP) 4.16   4.16 

Labeo dero (LD) 1.45 1.58  1.53 
Aplocheilus lineatus (AL) 1.13   1.13 

Ambassis gymnocephalus (AG) 2.77  1.22 1.62 
Gerres oblongus (GO)   1.51 1.51 

Stolephorus commersoni (SC)   1.13 1.13 
Carangoides malabaricus (CM)   2.42 2.42 

Therapon jarbua (TJ)   1.00 1.00 
Etroplus suratensis (ES)  2.82  2.82 

Hemiramphus xanthopterus (HX)  1.00  1.00 
Sillago sihama (SS)   1.00 1.00 

Upeneus vittatus (UV)   1.00 1.00 
Leiognathus equulus (LE)   1.34 1.34 

Johnius aneus (JA)   1.00 1.00 
Sphyraeno jello (SJ)   1.00 1.00 

Liza tade (LT)   1.22 1.22 
Xenentodon cancila (XC)   1.22 1.22 
Glossogobius giurus (GG)   1.00 1.00 

Channa gachua (CG)   1.00 1.00 

 

Only very few species showed temporal 
consistency in diet breadth. In BB, the breadth 
was almost consistent with minor variations (1.00 
- 1.31) among the three seasons. The diet breadth 

of Gerres oblongus (GO) varied between 1.00 
during premonsoon and 1.47 during post 
monsoon. During the postmonsoon, when more 
number of estuarine fishes was caught and the 



East Afr. J. Biophys. Comput. Sci., Vol. 2, Issue 1 
 

breadth of most of them was 1.00. Based on the 
diet breadth, the fishes in Vamanapuram can be 
classified as specialists (B < 3.00) and generalists 
(B > 3.00) and out of the 16 species occupying 
the freshwater region, 7 were specialists and 9, 
generalists. Out of the 7 specialists, 3 species 
were specialised to feed on the surface and 4 on 
bottom. Among the surface feeding specialists, 

DA was an important member of the community 
since it contributed to 13.55% of the total fish 
collected. According to Arunachalam et al. 
(1988), this species was a typical specialist 
feeding on the terrestrial insects. Barilius bakeri 
(BB), another specialist had a diet breadth of 1.18 
and AL, 1.13.  

 
Fig. 1: Seasonal variations in diet breadth of fish species in Vamanapuram River 
 

The bottom specialists were PV (2.78), GM 
(2.21), Puntius sarana (PS) (2.54) and LD 
(1.53). Among these, PV, GM and PS were 
herbivores feeding mainly on plant matter 
whereas LD was a carnivore feeding mainly on 
chironomid larvae. The important generalists 
were PA (6.64), PF (4.15), PM (5.14), PT (3.41) 
and Amblypharyngodon microlepis (AP) (4.16). 
Among these, PT and AP were herbivores. Most 
of the estuarine fishes were specialists feeding on 
fish. Temporal variations in diet breadth were 
noticed in almost all species and in general it was 
rather high during premonsoon season. According 

to Welcome (1979), differential prey 
availabilities, optimal foraging or interspecific 
competition could explain changes in diet breadth 
of a fish. The seasonal variations observed in the 
present study may be due to the differential food 
availabilities. Arunachalam et al. (1990) reported 
relatively low densities of invertebrates during the 
monsoon (wet) season in the stream pools of 
Kallar River. Various studies show that food 
availability was low during the dry season i.e. 
premonsoon in the present study (Zaret and Rand, 
1971 and Power, 1983 in Panama; Matthes, 1964 
in Zaire). The high diet breadth values observed 
during premonsoon may be due to the low food 

0

1

2

3

4

5

6

7

PA PF DA RD PT PV PM GM PS BB EM MA MM AP LD AL AG GO SC CM TJ ES HX SS UV LE JA SJ LT

Species

Di
et

 b
re

ad
th

Premonsoon

Monsoon

Postmonsoon

31



East Afr. J. Biophys. Comput. Sci., Vol. 2, Issue 1 
 

availability of their choice and fishes switched 
over to other items of food. On the other hand, 
Moyle and Senanayake (1984) hypothesised that 
the relative consistency of the environment during 
dry season enabled the development of 
autochthonous food. This fact may also be true in 
the present study for the high diet breadth values 
noticed during dry season. The breadth of PA 
during premonsoon and monsoon were found to 
be 6.28 and 6.35, respectively. The breadth was 
4.17 during post monsoon. During post monsoon 
the fish consumed a major percentage of small 
algae whereas in other seasons it consumed more 
of chironomid larvae. Similarly, PF had a diet 
breadth of 5.59 during premonsoon whereas 
during monsoon and postmonsoon, it was 3.18 
and 3.65 respectively. Similarly, PT, PM and EM 
also showed relatively high values during 
premonsoon season. 

Comparing the diet breadth values of fish species 
in different habitats, Habitat -I showed high 
values. The exceptions were PT and LD. The 
high segregation of bottom feeding fishes in 
riverine habitat observed in food overlap studies 
supports the high specialisations (low breadth 
values) noticed in this habitat. The interspecific 
competition may also be responsible for the high 
diet breadths observed in Habitat- I, since species 
richness is high in streams and more competition 
for the available food. E. maculatus (EM) had the 
maximum difference in diet breadth between the 
habitats (Habitat I - 4.36, Habitat- II - 2.44 and 
Habitat III – 1.00). It consumed more filamentous 
algae and littoral vegetation (58% and 23%, 
respectively) in riverine habitat. In the stream 
habitat, its food was mainly chironomid larvae 
(41%). Another fish which displayed much 
spatial difference in its food spectrum was RD 
(3.33 and 2.06 in Habitat I and Habitat II,  
respectively). The difference lies in the fact that 

the fish consumed a high percentage of terrestrial 
insects (67%) in the riverine habitat whereas it 
consumed a lower percentage (45%) of the same 
in the stream habitat. The streams which have 
comparatively more canopy cover are supposed 
to harbour more of terrestrial insects than the river 
habitat. Moreover, the trend is reverse with this 
fish in the present study. A similar reverse trend 
is observed in DA also. Thus the quantity of 
terrestrial insects available per fish is higher in 
rivers than in streams which in turn may be a 
factor for the high consumption of terrestrial 
insects in rivers. 

Conclusion 

Vamanapuram River, one of the major rivers of 
Kerala, is rich in fish species. The diet breadth 
study undertaken for different fish species of the 
river showed that the food preference greatly 
relied on habitat preference and feeding habits 
of the fish. Both specialists and generalists are 
found in the habitats. In general, the riverine 
habitat showed low diet breadths than lowland 
stream habitats. Estuarine fishes showed very low 
diet breadth indicating the dominance of 
specialists. Puntius amphibious showed the 
highest diet breadth followed by Mystus 
montanus and Puntius melanampyx.  

Acknowledgements 

The senior author is thankful to Professor 
P.Natarajan, the then Head of the Department of 
Aquatic Biology and Fisheries, University of 
Kerala, India, and Dr. Koos Vijverberg, 
Limnological Research Institute. Specicial 
thanks also extend to the Netherlands for their 
support and advice in carrying out this research 
work under the collaborative research project 
‘River Ecology, India’ sponsored by NIOO and 

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East Afr. J. Biophys. Comput. Sci., Vol. 2, Issue 1 
 

the Office of the International Co-operation of 
the University of Leiden, The Netherlands.  

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communities of a South Indian River, Ph.D. 
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Arunachalam M., Madhusoodhanan Nair K.C., 
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David Kingston S. 1992. Niche segregation of fish 
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Heng K., Chevalier M., Lek S. and Laffaille P. 2018. 
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Julio Cesar Sa-Oliveira, Ronaldo Angelini and Isaac 
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Levins R. 1968. Evolution in changing 
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Matthes H. 1964. Les poisons du lac Tumba et de la 
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partitioning among the fishes of rainforest 
streams in Srilanka.  Journal of Zoology 
(London). 202 : 195 – 223. 

Pisharody P.R.1987. Monsoon vagaries over Kerala.  
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Abdul Aziz (eds.).  Advances in Aquatic 
Biology and Fisheries, Trivandrum, India. 361-
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Power M.E. 1983. Grazing responses of tropical 
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Saswata Maitra, Mahadevan Harikrishnan and 
Balachandran Nidhin,2019.Feeding strategy, 
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four mesopredatory catfishes of a tropical 
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Welcome R.L. 1979. Fisheries ecology of floodplain 
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	Cover V2.pdf (p.1)
	Cover.pdf (p.1-2)
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	blank page.pdf (p.2)
	Table of contents Vo 2.pdf (p.3-5)
	all articles vol 2.pdf (p.6-81)
	Volume 2 Issue 1_ 6 articles_4_3.pdf (p.6-91)
	4_Captive fish_Anna
	RESULTS AND DISCUSSION
	References

	3_Reproductive Disorder
	6_Diet bredth_Prof. Nat
	8_Ground water_Jeeva
	Base boundary map was prepared using Survey of India topo-sheets of the study area, and data such as rainfall, geomorphology, geology and land use were collected from central and state government agencies. During field study, groundwater samples were ...

	10_Ethnoveterinary Following comments
	Dagne et al_ Challenging students’ performance through Practical Skills Assessment.pdf (p.73-82)


	Guideline to Authors_ EAJBCs.pdf (p.82-90)
	Back cover.pdf (p.91)
	INTRODUCTION
	EXTENSION OF THE MODIFIED MODEL INTO AN OPTIMAL CONTROL
	Optimal protection and hospitalization using modified model
	Existence of an optimal control
	The Hamiltonian and optimality system

	Numerical simulations of optimal control problem
	Optimal control comparisons and strategies

	CONCLUSION
	INTRODUCTION
	INTRODUCTION

