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Proceedings of the NationalAcademy of Sciences, India Section B:Biological Sciences ISSN 0369-8211Volume 85Number 1 Proc. Natl. Acad. Sci., India, Sect. B Biol.Sci. (2015) 85:167-174DOI 10.1007/s40011-014-0338-3

Food and Feeding Ecology of the Non-native Nile Tilapia Oreochromis niloticus(Linnaeus, 1758) in the River Yamuna,India

Absar Alam, N. K. Chadha, K. D. Joshi,S. K. Chakraborty, Paramita BanerjeeSawant, Tarkeshwar Kumar, KalpanaSrivastava, et al.

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RESEARCH ARTICLE

Food and Feeding Ecology of the Non-native Nile TilapiaOreochromis niloticus (Linnaeus, 1758) in the River Yamuna,India

Absar Alam • N. K. Chadha • K. D. Joshi • S. K. Chakraborty •

Paramita Banerjee Sawant • Tarkeshwar Kumar •

Kalpana Srivastava • S. C. S. Das • A. P. Sharma

Received: 26 July 2013 / Revised: 7 December 2013 / Accepted: 3 March 2014 / Published online: 4 April 2014

� The National Academy of Sciences, India 2014

Abstract Nile tilapia Oreochromis niloticus is the dom-

inant invasive species of the river Yamuna. Gut analysis

showed that the majority of the food items ingested con-

sisted of Chlorophyceae, Myxophyceae, Bacillariophyceae

and detritus. Among the diatoms—Synedra spp. (80.75 %),

Melosira spp. (73.5 %), Cyclotella spp. (73 %), Meridion

spp. (71.75 %) and Nitzchia spp. (73.25 %), the green

algae—Ankistrodesmus spp. (71.00 %), Coelastrum spp.

(61.5 %), Scenedesmus spp.(52 %), Tribonema spp.

(49.5 %), Protococcus spp. (58.5 %), Oocystis spp.

(49.75 %) and Pediastrum spp. (49.5 %) and among blue

green algae, Oscillatoria spp. (70.5 %), Anacystis spp.

(61.5 %) and Phormidium spp. (46.5 %) showed high fre-

quency of occurrence. The Gastrosomatic Index in males

and females ranged from 0.23 to 0.93 and 0.25 to 1.1

respectively with no significant difference between males

and females throughout the year (t test, p [ 0.05). In

addition to this, higher percentage of males and females

showing low feeding intensity during all the months except

in January indicted the species to be the poor feeder.

However, the condition factor [1 suggested the species to

be in good condition throughout the year in both males and

females. Dominancy of detritus and pollution indicator

genera Synedra spp., Anacystis spp., Ankistrodesmus spp.,

Melosira spp., Nitzchia spp., Oscillatoria spp., Phormidi-

um spp. and Scenedesmus spp. suggested Nile tilapia to be

the cleaner of the polluted river Yamuna.

Keywords Invasive � Nile tilapia � Gastrosomatic Index �Condition factor � Food � Yamuna

Introduction

Nile tilapia, Oreochromis niloticus (Linnaeus) is indigenous

to Africa. It’s natural distribution ranges from the upper Nile

river southwards to the equator and west to the Atlantic

coast [1] while its introduced range has widened, covering at

least 85 countries of tropics, subtropics and temperate

environments [2]. Invasion of exotics is globally recognised

as the most serious threat, only after habitat loss and frag-

mentation to aquatic ecosystems and their biological

diversity. Nile tilapias, in particular are highly successful

invaders due to their environmental tolerance, successful

reproductive strategies and trophic plasticity [3, 4]. Further

profound modifications to the fluvial systems such as water

removal and waste discharge directly threaten the native fish

fauna mainly the Indian major carps and favour the invasion

of non-native species [5, 6]. However, a few studies have

been conducted in Indian rivers where these modifications

are prevalent. For example in the river Ganga dominant

catch of exotics (O. niloticus and Cyprinus carpio) in the

commercial landing negatively impacted the native carp

abundance as that of Labeo calbasu, Catla catla, Labeo

rohita and Cirrhinus mrigala in recent decades [7, 8]. Nile

tilapia has been successfully established in such vacated

habitats and is present year round in the river Yamuna [9,

10]. Unauthorised introduction of Nile tilapia in India is

A. Alam (&) � K. D. Joshi � K. Srivastava � S. C. S. Das

Regional Centre, Central Inland Fisheries Research Institute,

24-Pannalal Road, Allahabad 211002, Uttar Pradesh, India

e-mail: absar_alam@rediffmail.com

N. K. Chadha � S. K. Chakraborty � P. B. Sawant � T. Kumar

Central Institute of Fisheries Education, Versova, Andheri

(West), Mumbai 400 061, India

A. P. Sharma

Central Inland Fisheries Research Institute, Barrackpore,

Kolkata 700 120, West Bengal, India

123

Proc. Natl. Acad. Sci., India, Sect. B Biol. Sci. (Jan–Mar 2015) 85(1):167–174

DOI 10.1007/s40011-014-0338-3

Author's personal copy

reported to have taken place, sometimes in the 1980s [11]. It

possibly entered the river Yamuna through the escape from

the aquaculture facilities. The gradual appearance of tilapia

in the river Yamuna was noticed since a couple of years, but

it is now spreading in the system at an alarming rate. Tilapia

started to appear in catches from July 2005 and formed a

catch of about 100 kg in 2005 [9], reached to 36.3 t in 2010

[10] at Allahabad from the river Yamuna.

Earlier studies carried out in east Africa described the diet

of O. niloticus as predominantly herbivorous, comprising

mainly of algae, benthic diatoms and detritus material [3, 12,

13] and omnivorous [14, 15]. However, information on the

food and feeding of O. niloticus is lacking in the Indian

context. The present work was undertaken to understand the

current status of food and feeding habits of the O. niloticus

and to add to the existing knowledge of the species which

would help in the management of the fishery. The knowl-

edge on the type of natural food is needed in ascertaining

whether the population age structure in the fishery is in

proper relation to the available food resources.

Material and Methods

Study Area

Fish specimens were collected at monthly intervals from the

commercial catches landed at Sadiapur landing centre in

Allahabad district of Uttar Pradesh, India (N 25.42140� and

E081.82479�). Location of the sampling site was recorded by

Global positioning system (GARMIN, GPSmap76CSx).The

river Yamuna originating from the Yamunotri in the Hima-

layas, is one of the main tributaries of the river Ganga and

contributes significantly to the local fishery(Fig. 1). River

Yamuna has a strong pattern of flow–low flow in summer and

winter and flash floods during monsoon. Of the total catch-

ment area of 3, 45, 848 km2, 27.5 % is non-arable, 12.5 %

forest and 60 % cultivable land [16]. The river bed is gen-

erally sandy with substantial top layer of mud and silt. The

mean air temperature ranges between 8.7 and 42.3 �C. It is

high in May and June and low in December and January.

Average annual rainfall is 1,027 mm with maximum rains

occurring between July to September.

Sampling Procedure

A total of 399 freshly caught fishes of different sizes were

collected early morning at monthly intervals from the

Sadiapur landing centre located on the bank of the river

Yamuna, Allahabad from October 2011 to September

2012. Their weight and length to nearest gram and mm

were measured. The specimens were dissected, their

stomachs removed and preserved in specimen bottles

containing 4 % formalin. The intensity of feeding was

visually assessed based on percentage of stomachs in dif-

ferent degrees of distension such as gorged, full, 3/4 full,

1/2 full, 1/4 full and empty [17]. Fishes were considered as

active feeders with gorged and full stomach, moderately

with 3/4 and 1/2 full stomach and poorly fed with 1/4 and

empty stomach. Food items were identified under the 4009

magnification up to the generic level. Other method for

estimating feeding intensity is Gastrosomatic Index (GaSI).

GaSI was calculated following Le Cren [18] as:

GaSI ¼ Weight of the stomach

Total weight of the fish� 100:

The percentage occurrence of each food item was

estimated by multiplying the ratio of the number of times

Fig. 1 Map showing the sampling centre on the river Yamuna at

Allahabad

168 A. Alam et al.

123

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an item occurred to the total number of guts analysed by a

hundred. The condition of the fish was expressed by

Fulton’s condition factor (K), calculated using the

following formula:

K ¼ 100 W

L5;

where W total weight in gram and L total length in mm.

Results and Discussion

A total 399 specimens of Nile tilapia consisting of 192

male and 207 females were examined. The mean body

weight, mean total length, stomach weight of males were

350.16 ± 12.66 g, 252.6 ± 2.80 mm and 1.78 ± 0.13 g

and that of females were 340.15 ± 8.61 g, 254.01 ±

2.20 mm and 1.62 ± 0.13 g respectively. Stomach weight

ranged between 0.24–12.86 g in males and 0.4–17.6 g in

females. There was no significant difference in the mean

total body weight, total length and stomach weight in males

and females (t test, p [ 0.05).

Percentage Occurrence and Composition of Food Items

The percentage occurrence of different food items ingested

by O. niloticus is depicted in Table 1. Phytoplankton and

detritus constituted the most frequent food items of O.

niloticus. Diatom (Baccilariophyceae), green algae (Chlo-

rophyceae) and blue green algae (Cynophyceae) were

found to occur together. Among the diatoms, Synedra spp.

(80.75 %), Melosira spp. (73.5 %), Cyclotella spp. (73 %),

Meridion spp. (71.75 %) and Nitzchia spp. (73.25 %)

showed high frequency of occurrence and Pinnularia spp.

(9.5 %), Amphora spp. (8.5 %) and Denticula spp.

(0.75 %) showed low percentage of occurrence. Among the

green algae, Ankistrodesmus spp. (71.00 %), Coelastrum

spp. (61.5 %), Scenedesmus spp. (52 %), Tribonema spp.

(49.5 %), Protococcus spp. (58.5 %), Oocystis spp.

(49.75 %) and Pediastrum spp.(49.5 %) were found to

show high occurrence. Among blue green algae, Oscilla-

toria spp. (70.5 %), Anacystis spp. (61.5 %) and Phormi-

dium spp. (46.5 %) showed high frequency of occurrence.

Chironomids occurred in 22.75 % of the total stomachs

analysed. Though the frequency of occurrence of zoo-

plankton ranged between 15 and 22 %, their relative

abundance was low and is in agreement with the findings

that zooplankton avoid predation by O. niloticus [19]. The

analysis of gut content of Nile tilapia showed great diver-

sity in food items and consisted 20 genera of diatoms, 17

genera of green algae, 8 genera of blue green algae, 1 genus

of macro-benthic invertebrates (Chironomous spp.) and

microscopic copepodid eggs. The composition of the diet

varied seasonally. Chlorophyceae, Myxophyceae and

detritus dominated the diet of the Nile tilapia in most parts

of the year. During October to February, the dominant food

items were Tribonema spp. followed by Melosira spp.,

Microspora spp. and Merismopedia spp. In between

December and January, maximum number of gorged

stomachs observed were with decomposed vegetable

material. During April to September, Anacystis spp.,

Merismopedia spp., Pediastrum spp. and Oscillatoria spp.

occurred in abundance possibly due to their preference to

strong solar radiation and high temperature. Melosira spp.,

Synedra spp., Cyclotella spp., Nitzchia spp., Oscillatoria

spp. and Ankistrodesmus spp. were found to occur

throughout the year. Detritus, chironomids and Merismo-

pedia spp. showed an increasing trend in the percentage of

occurrence with the fish size. Examination of O. niloticus

diets showed high percentage of mud and detritus (53.5 %)

and epipelic algae like Synedra spp., Nitzchia spp., Meri-

dion spp. etc. suggested that it is a bottom grazer in addi-

tion to being filter feeder.

Feeding Intensity in Relation to Month

Variations in feeding intensity were observed throughout

the year. Empty and 1/4 full stomach signified cessation of

feeding or lowest feeding intensity. In both male and

females, low feeding intensity was observed during all the

months except in January for both males and females

(Figs. 2, 3). Low feeding was observed in April (100 %) in

females as well as in males (85.7 %). Highest percentage

of gorged stomachs were found in December (25 %) in

males and during January (53.3 %) in females and lowest

between April to July and September respectively. In

females, highest percentages of full stomachs (18 %) were

seen in October and December and for males (15 %) in

October, November and December respectively. In males

none of the full stomachs were recorded in April and July

and in females lowest percentage were observed in April to

July (0–6.6 %) and September (8.3 %). Similarly, the

percentage of occurrence of empty stomachs ranged from

13.3 % (January) to 78.5 %) (April) in males and 21 %

(October) to 77.7 % (April) in females. The present results

indicate the species to be a low to moderate feeder with no

profound differences in the month-wise intensity of feeding

except in January when both males (40 %) and females

(46.66 %) are active feeders. During summer season,

majority of fishes were poorly fed (71 %) as compared with

monsoon (52 %) and winter (37 %). Highest percentages

of active feeders were observed in the winter (33.7 %)

followed by monsoon (20.5 %) and lowest in summer

(12.2 %) signifying seasonal differences in feeding inten-

sity. The poor feeding intensity in summer may be attrib-

uted to stress during spawning during April to June. The

Food and Feeding Ecology of Nile Tilapia 169

123

Author's personal copy

higher percentage of active feeders in winter signified it to

be the feeding phase [20].

Feeding Intensity in Relation to Length

Highest feeding intensity was observed in the length group

315–334 mm with 50 % of gorged and full stomachs fol-

lowed by 295–314 mm (23.5 % of gorged stomachs) in

females (Fig. 4). However, highest feeding intensity was

seen in length groups 355–374 mm with 32 % of gorged

and full stomachs and lowest in the length groups

155–174 mm in males (Fig. 5) but highest percentage of

gorged stomachs were found in the length group

235–254 mm (17.4 %). The males showed an increasing

trend in feeding from 295–314 to 355–374 mm length

while in females, the increasing trend was observed from

155–174 to 195–214 mm and 275–294 to 315–334 mm

length groups respectively. The percentage of poorly fed

fishes ranged between 41 % (315–334 mm length group)

and 61.1 % (295–314 mm length group) in males, whereas

it ranged between 23.5 % (295–314 mm length group) and

63.8 % (235–254 mm length group) in females. The ana-

lysis of feeding intensity in relation to fish size reveals the

species to be poorly fed in both the sexes except in length

group 315–334 mm in females.

Gastrosomatic Index and Condition Factor

The GaSI of males and females in the different months is

presented in Table 2 and Fig. 6. The gastrosomatic index

in males and females ranged from 0.23 to 0.93 and

0.25–1.1 respectively. However, there are no significant

differences in the GaSI between males and females

throughout the year (t test, p [ 0.05). The gastrosomatic

index of both males and females were less than 1 in all the

months except in females in January indicating it to be

poorly fed. The condition factor has been used to measure

various ecological factors such as gonadal maturation,

Table 1 Percentage occurrence of different food items in the stom-

ach of Oreochromis niloticus from Allahabad, river Yamuna

Sl. no. Food items Occurrence Percentage

occurrence

Bacillariophyceae

1 Synedra 323 80.75

2 Melosira 294 73.5

3 Anomoenoeis 54 13.5

4 Gyrosigma 118 29.5

5 Stephanodiscus 187 46.75

6 Fragilaria 161 40.25

7 Navicula 124 31.00

8 Cyclotlella 292 73.00

9 Tabellaria 141 35.25

10 Asterionella 183 45.75

11 Nitzchia 293 73.25

12 Pinnularia 38 9.50

13 Cymatopleura 56 14.00

14 Aulacoseira 183 45.75

15 Eunotia 87 21.75

16 Cymbella 152 38.00

17 Amphora 34 8.50

18 Stauroneis 80 20.00

19 Meridon 287 71.75

20 Denticula 3 0.75

Chlorophyceae

21 Tribonema 198 49.5

22 Coelastrum 250 62.50

23 Protococcus 234 58.50

24 Pediastrum 198 49.50

25 Ankistrodesmus 284 71.00

26 Scenedesmus 208 52.00

27 Actinastrum 68 17.00

28 Chorella 58 14.50

29 Microspora 154 38.50

30 Oocystis 199 49.75

31 Crucigenia 99 24.75

32 Gleocystis 125 31.25

33 Cosmarium 110 27.50

34 Gonium 90 22.50

35 Pandorina 68 17.00

36 Kirchnerilla 102 25.50

37 Mougeotia 15 3.75

Myxophyceae

38 Oscillatoria 282 70.50

39 Anacystis 246 61.50

40 Phormidium 187 46.75

41 Merismopedia 153 38.25

42 Nostoc 105 26.25

43 Euglena 85 21.25

44 Anabaena 64 16.00

Table 1 continued

Sl. no. Food items Occurrence Percentage

occurrence

45 Spirulina 115 28.75

Zooplankton

46 Moina 88 22.00

47 Brachionus 60 15.00

Macrobenthic invertebrates

48 Chironomus 104 22.75

Other items

49 Detritus 213 53.25

50 Copipodid eggs 16 4.00

170 A. Alam et al.

123

Author's personal copy

degree of fatness and well-being of an organism [21].

Condition factor ranged from 1.9 to 2.3 and 1.8 to 2.2 in

males and females respectively (Table 2; Fig. 7). The high

values of condition factor in January in males (2.25) and

females (2.2) coincide with higher values of GaSI, might

possibly be due to active feeding intensity in both the

sexes. The lower values of GaSI and higher values of

condition factor in April might be due to low feeding

intensity and peak breeding period. The average values of

condition factor in both males and females being greater

than one indicates the species to be in good health

throughout the year. The mean K value of O. niloticus from

0%10%20%30%40%50%60%70%80%90%

100%

Perc

enta

ge

Month

Low feeding Moderate feeding High feeding

Fig. 2 Month-wise feeding intensity in O. niloticus (male)

0%10%20%30%40%50%60%70%80%90%

100%

Per

cent

age

Month

Low feeding Moderate feeding High feeding

Fig. 3 Month-wise feeding intensity in O. niloticus (female)

010203040506070

Per

cent

age

Length group in mm

Low feeding Moderate feeding Active feeding

Fig. 4 Length-wise feeding intensity in O. niloticus (female)

010203040506070

Per

cent

age

length group in mm

Low feeding Moderate feeding Active feeding

Fig. 5 Length-wise feeding intensity in O. niloticus (male)

Food and Feeding Ecology of Nile Tilapia 171

123

Author's personal copy

Ethiopian Rift valleys varied from 1.81 to 1.87 [22] and

from Bangladesh it varies in genetically improved strains

of Nile tilapia from 1.343 to 1.871 for GIFT (5th genera-

tion) and 1.385 to 1.825 [23] for GIFU (11th generation).

Higher values in the study period indicated the robust

character of individuals of Nile tilapia from river Yamuna

over that of Ethiopian lakes and GIFT and GIFU strains of

Nile tilapia. The nearer the useful end product stands to the

first link in the food chain, the higher the yield from the

water mass [24]. Algae and detritus are the important

components of diet forming the first link in the food chains

resulting in efficient utilization of energy in the aquatic

ecosystem and hence better growth of the fish.

The present study revealed that Nile tilapia in Yamuna

river feeds largely on phytoplankton and detritus is in

agreement with similar findings in lake Victoria [25–27].

Stomach contents of O. niloticus suggested it to be an

opportunistic feeder with the availability of the broader

food base. Chironomid larva (Diptera) is an important

herbivore of the aquatic ecosystem owing to their ubiquity,

high densities and short generation time [28]. The occur-

rence of phytoplankton/detritus, zooplankton and chirono-

mids in the diet showed the species to feed on more than

one trophic level in the food web suggesting the species to

be omnivorous in food habit. Dietary plasticity over other

native fish species that did not express such flexibility (like

Catla catla which is primarily a zooplanktivorous) may

have contributed to the success of Nile tilapia in the river

Yamuna.

0

0.2

0.4

0.6

0.8

1

1.2G

astr

o So

mat

ic I

ndex

(GaS

I)

Month

Male

female

Fig. 6 Month-wise Gastro Somatic Index in O. niloticus

Table 2 Month-wise estimated Gastro Somatic Index and condition factor of O. niloticus

Length group (mm) No. of male No. of female Gastrosomatic Index (GaSI) Condition factor (K)

Male Female Male Female

October 21 32 0.41 0.40 1.90 1.80

November 25 30 0.55 0.55 1.97 2.10

December 32 28 0.67 0.53 2.04 2.14

January 15 15 0.93 1.10 2.25 2.20

February 14 11 0.80 0.52 2.30 2.22

March 16 13 0.40 0.63 2.13 2.19

April 14 9 0.23 0.25 2.05 2.13

May 12 17 0.42 0.36 1.98 1.95

June 11 15 0.46 0.41 1.93 1.91

July 11 14 0.39 0.33 2.00 2.04

August 10 11 0.58 0.44 1.96 1.95

September 11 12 0.38 0.29 1.91 1.85

Total 192 207

1

1.2

1.4

1.6

1.8

2

2.2

2.4

Con

diti

on F

acto

r (K

)Month

Males

Females

Fig. 7 Month-wise condition factor (K) in O. niloticus

172 A. Alam et al.

123

Author's personal copy

The decline of the diverse and trophically complex

native fish community, in particular the Indian major carps,

might have allowed the increase of their main food sources

including phytoplankton, zooplankton and macroinverte-

brates in the river Yamuna. After Cyprinus carpio, O.

niloticus is the dominant fish landed from the Yamuna [7,

8, 10]. This may have initiated changes in food web

structure. The cascading effect of the introduced Nile perch

into the lake Victoria on the food web has also been

reported [27]. If the declining Indian major carp fisheries

re-establish in the former trophic position and abundance,

they may upset the growth and condition of Nile tilapia in

the river Yamuna.

Further, river Yamuna is among the most polluted rivers

in the world. Industrial and municipal sewage released

directly into the river without any treatment have resulted

in dramatic ecological changes [16, 29–31]. Dominancy of

pollution indicator genera Synedra spp., Anacystis spp.,

Ankistrodesmus spp., Melosira spp., Nitzchia spp., Oscill-

atoria spp., Phormidium spp. and Scenedesmus spp. among

algae and detritus suggest Nile tilapia to be the cleaner of

the polluted river Yamuna.

Conclusion

Management of the fisheries and the aquatic system that

support them requires the knowledge of the food web

ecology. Much attention has been given to Indian major

carps over the last two decades and relatively less impor-

tance on the development and impact of feeding habits of

Nile tilapia. Understanding of the present trends in food

and feeding habits of Nile tilapia is very critical in pre-

dicting its fisheries in dynamic riverine system.

Acknowledgments The first author is thankful to the Director CIFE

Mumbai, the Director CIFRI Barrackpore and the Indian Council of

Agricultural Research (ICAR), New Delhi, permitting to carrying out

the research work as part of the Ph.D. Programme.

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