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INTRODUCTION
The Ganga River (Ganges) is known to harbour rich
fish diversity (Bilgrami 1991, Rao 2001, Kapoor et al.
2002, De Silva et al. 2007); however, environmental
integrity of this largest freshwater river systems of the
country is being increasingly threatened due to anthro-
pogenic activities such as river course diversions and con-
struction of barrage, dams etc. (Sinha and Khan 2001,
Sarkar and Bain 2006) and also through exotic fish intro-
ductions (De Silva et al. 2006, García-Berthou 2007, Lakra
et al. 2008). Freshwater fish biodiversity of the Ganga
River is enormous (Bilgrami 1991, Kapoor et al. 2002, De
Silva et al. 2007, Lakra et al. 2009) and the reported
impacts of alien fish species emphasized biodiversity
threats and conservation (Singh and Lakra 2006, De Silva
et al. 2007, Lakra et al. 2008). Ganga is the largest river
basin in Asia having highest level of endemism and fish
diversity (De Silva et al. 2007). The growing pollution of
the river Ganga in recent years makes a noticeable change
in its physico-chemical characteristic and the water quality
ACTA ICHTHYOLOGICA ET PISCATORIA (2010) 40 (1): 11–19 DOI: 10.3750/AIP2010.40.1.02
*Correspondence: Dr. A.K. Singh, Principal, Senior Scientist, National Bureau of Fish Genetic Resources, Canal Ring Road, P.O. Dilkusha, Lucknow-226002,
Uttar Pradesh, India, phone: +91-522-2442440, +919450355685, fax: +91-522-2442403, e-mail: aksingh56@rediffmail.com.
INVASION OF AN EXOTIC FISH—COMMON CARP, CYPRINUS CARPIO L.
(ACTINOPTERYGII: CYPRINIFORMES: CYPRINIDAE) IN THE GANGA RIVER,
INDIA AND ITS IMPACTS
Atul K. SINGH*, Ajey K. PATHAK, and Wazir S. LAKRA
National Bureau of Fish Genetic Resources, Lucknow, India
Singh A.K., Pathak A.K., Lakra W.S. 2010. Invasion of an exotic fish—common carp, Cyprinus carpio L.
(Actinopterygii: Cypriniformes: Cyprinidae) in the Ganga River, India and its impacts. Acta Ichthyol.
Piscat. 40 (1): 11–19.
Background. The Ganga River (Ganges) is known of its rich fish diversity which is adversely affected by
degrading environmental and ecological conditions. There are more than 300 exotic fish species in India. Many
of them (particularly Cyprinus carpio) escaped from confinement and are now present in the Ganga River, chal-
lenging its ecological equilibrium. The aim of this project was to study the population characteristics of Cyprinus
carpio (i.e., the abundance, size range, food and feeding, gonado-somatic index (GSI), gonad maturity stage,
maturity and breeding) and the altered fishery dynamics.
Materials and Methods. The commercially caught fishes, including the exotic ones, were identified, examined
and measured. Important indices such as: the abundance index of exotic fishes, the gonado-somatic index (IG),
as well as the gonad maturity stage of the escapee C. carpio were determined. The gut content was also analyzed
to identify food items and thereafter the food richness, diet breadth, and gut repletion index (GRI%) were calcu-
lated using the Simpson’s diversity index.
Results. C. carpio introduced about sixty years ago for aquaculture has now been found to invade into the Ganga,
the largest river of the country contributing significantly to the fishery. The abundance index of C. carpio ranged
from 12.2% to 45.5 % in 250 km long river stretch of the Ganga River flowing along Kanpur to Varanasi in the
state of Uttar Pradesh. The gut content analysis revealed the presence of Eichhornia (9.8%), Pistia (11.6%),
Nymphaea (8.5%), annelids worms (7.8%), algae (20.2%), mud and detritus (14.8%). The calculated diet breadth
ranged from 0.82% to 0.91%; food richness ranged from 12 to 16, and the gut repletion index (GRI%) was 100%
at different sampling sites. Mature females represented all the six reproductive stages with varying gonado-
somatic index (IG) (0.5 to 30) in different catches. Presence of spent, ripe, and mature females was recorded.
Conclusion. Abundance of exotic fish primarily C. carpio and Oreochromis niloticus in the fishery of the Ganga
River was observed. The gonado-somatic index (IG) and the presence of all the six gonadal stages confirmed that
C. carpio established its breeding population. The dominant catch of exotic fishes negatively impacted on the
important indigenous fishes particularly Indian major carps (Catla catla,Labeo rohita, and Cirrhinus mrigala).
The change in dynamics of the fishery due to the presence of common carp attracted attention to conserve rich
indigenous germplasm facing threats of shifting from their natural habitats.
Keywords: Exotic fish, Cyprinus carpio, introduction, breeding, biodiversity, conservation
to an extent that the fish community is affected (Sarkar and
Bain 2006, Khanna et al. 2007) and the fish yield as well as
biodiversity has decreased (Sinha and Khan 2001). The
growing siltation due to various anthropogenic activities
and the unavailability of the fish food has also been report-
ed to disturb the fish breeding grounds particularly the
Indian major carps (Rao 2001, Sinha and Khan 2001).
The common carp, Cyprinus carpio L., is extensively
translocated species around the world (Sivakumaran
et al. 2003, De Silva et al. 2006, Lakra et al. 2008) includ-
ing India where it was introduced in 1959 for aquaculture
purpose (Singh and Lakra 2006). In India, it was studied for
more than a decade under All India Coordinated Research
Project for developing it as a species under composite fish
culture. Consequently, three Indian major carps (Catla
catla,Labeo rohita, and Cirrhinus mrigala), Chinese carps
(Ctenopharyngodon idella and Hypophthalmichthys
molitrix), and common carp (Cyprinus carpio) were adopt-
ed together in composite fish culture (Jena et al. 2002). The
Bangkok strain of common carp (C. carpio communis) is
widely used under aquaculture in plains while mirror carp
(C. carpio specularis) is used for aquaculture in upland
waters of hill states. Common carp has augmented fish pro-
duction (Jena et al. 2002) in the country and is cultivated in
different agroclimatic conditions. While Chinese carps
including bighead carp, Aristichthys nobilis, and common
carp are widely cultivated exotic carps, more than 300 exot-
ic fish species have also been introduced into India from
other countries intentionally or illegally for aquaculture,
sports, mosquito control, and aquarium purposes (Singh
and Lakra 2006, Lakra et al. 2008). Escapement of exotic
fishes due to recurring floods or inadvertent releases fre-
quently happened but the occurrence of escapee exotic fish-
es in the fishery of the Ganga River was never known. The
recent appearance of exotic fishes particularly C. carpio in
the fishery of the Ganga River prompted us to study its pop-
ulation characteristics i.e., the abundance, size range, food
and feeding, gonado-somatic index (GSI), maturity, and
breeding. Therefore, this study was undertaken under two
perspectives; the former was to ascertaining the coloniza-
tion of the escapee C. carpio through natural population in
the Ganga River and the latter was to assess its possible
impacts on the dynamics of the local fishery.
MATERIALS AND METHODS
The state of Uttar Pradesh is the most densely populated
state of the country. Agriculture and allied activities form
the backbone of its economy. Being land-locked, it is
endowed with an abundant supply of inland water resources
(1165 million ha) that are ideal for fisheries and aquaculture.
The availability of 0.72 million ha of running water in the
form of rivers and canals enriches the state with plenty of
ichthyofaunal diversity (Bilgrami 1991, Kapoor et al. 2002).
The faunal resources of the Ganga have distinct characteris-
tic feature and fall into three zones (i) the upper Ganga River
in hilly terrain, (ii) the middle Ganga River flowing in the
states of Uttar Pradesh, Bihar, and (iii) the deltaic tract of the
lower Ganga in the state of West Bengal (Rao 2001).
The study area covered approximately 250 km of the
river stretch of the middle Ganga flowing along the dis-
tricts of Kanpur, Allahabad, Varanasi, and Mirzapur in
the state of Uttar Pradesh. Allahabad lies at the junction of
the two other major cities Kanpur and Varanasi along the
Ganga. Three main fish landing areas at Allahabad:
Daraganj, Sadiyapur, and Jhunsi; three in Varanasi the
Rajghat, Saraimohana, and Ramnagar, bridge area in
Kanpur, Shuklaganj in Unnao and Adalhat in Mirzapur
district were the study sites as demarcated in Fig. 1.
Singh et al.
12
Fig 1. Map of the study area in the Ganga River
Fish samples were collected from the landing centres on
quarterly basis during 2004 through 2008. Fishermen gen-
erally used multi-meshed gill nets of mesh size 8.5–50 mm
as well as dragnets for fishing. From commercial catches,
fishes were collected at the landing centres and were iden-
tified, measured (fork length, FL nearest mm), and weighed
(nearest g) using portable digital balance. Keys for identifi-
cation of fish species was followed as given by Jhingran
(1975) and FAO identification sheet as given by Fisher and
Bianchi (1984). From the total catch, the abundance index
of exotic fish was calculated using the following formula:
Where:
AI = abundance index,
n(k) = number of exotic fish caught at each study site,
N= number of all the fish species caught at that site.
The fish catches were sorted by species by fishermen
for marketing and sale. The data from such segregated
fish groups were then collected to work out the species
contribution. From the catch, C. carpio was separately
counted, sexed as male and female and the gonads of
immature, maturing, mature and spent fish were dissected
out, weighed and fixed in 10% formalin for microscopic
examinations. The gonado-somatic index (IG) was calcu-
lated from IG=M
G(MT– MG)–1 where MGis gonad mass
and somatic mass was total mass (MT– MG).The fecundi-
ty of individual females was determined gravimetrically,
and the gonad maturity stages were determined according
to Nagelkerke and Sibbing (1996).
The intestines of 50 collected specimens from differ-
ent sampling sites were cut and fixed in 5% formalin for
gut content analysis. The diet and feeding habits of
C. carpio were determined based on the contents of the
digestive tract and was examined using Leitz dissecting
microscope. Different taxa of the food items were identi-
fied, counted, and the food richness, diet breadth, and gut
repletion index (GRI%) were calculated using the
Simpson’s diversity index (Begon et al. 1986).
The length–weight regression was calculated by the
method of least squares by grouping the sample data into
several short length groups and fitting the regression of
logarithmic value of the average weight of fishes. The
grouping was done according to the size ranges of the col-
lected fish. The degree of adherence was then determined
on the basis of length–weight regressions and it was cal-
culated using the following formula:
Where:
n= total number of length group,
x= mean of x(length),
y= mean of y(weight).
RESULTS
The important fish biodiversity of the Ganga River col-
lected between Kanpur and Mirzapur were identified and
details of their taxonomy, habitat, size range and conserva-
tion status were synthesized and presented in Table 1.
The catch composition of the commercially important
fish diversity grouped as Indian major carps (IMCs),
minor carp, catfishes, miscellaneous, and exotic fishes
was calculated. The Indian major carps comprising of
Catla catla,Cirrhinus mrigala, and Labeo rohita consti-
tuted 5% to10 % of total catch and their size ranged from 200
to 550 mm in length and 400 to 8000 g in weight. The IMCs
included high proportion of large fish weighing 3–7 kg and
the small fishes were in low proportion. The proportion of
Labeo rohita caught was remarkably low. It was also
observed that there was a decline in catch of IMCs over
the years during the study period. The minor carps in the
total catch were mainly represented by Labeo bata,L. cal-
basu,Cirrhinus reba,Puntius sophore, and P. conchonius
and they constituted 5%–7% with size range of 90 to 250
mm in length and 150–1500 g in weight. Catfishes in gen-
eral were represented by Sperata aor,S. seenghala,
Wallago attu,Bagarius bagarius,Rita rita,Clupisoma
garua and constituted 10%–12% of the total catch having
common weight range of 600 to 2000 g. Other miscella-
neous fishes were Gonialosa manmina,Salmophasia
bacaila,Glossogobius giuris,Ailia coila,Johnius coitor,
Mastacembelus armatus, and Anabas testudineus repre-
senting 10%–15% of total catch (Table 2).
Cyprinus carpio was most dominating fish species in
all the catches from the Ganga River at all the sampling
stations (Fig. 2). It is to mention that there was no exis-
tence of C. carpio in the fishery of the Ganga River earli-
er. An assessment of the occurrence of exotic fishes for
the years 2004 and 2008 revealed that there was a decline
of 24.56% in total catch of local fishes whereas the catch
of exotic fishes increased by 115.8 percentage points
within four years (Fig. 3).
Gonadal examination of C. carpio in different catches
revealed that immature, maturing, and mature fishes were
available. Mature males were found at smaller size
(214 mm FL) while mature females were bigger in size
(324 mm FL) and sex ratio revealed slight variation (1 : 1.12)
in sex ratio (female : male) = 383 : 429 than the expected
Mendelian sex ratio of 1 : 1. Gonads of 132 examined
specimens from different locations of the river revealed
that mature female represented all reproductive stages
(1–6) with varying gonado-somatic index (IG= 0.5 to 30).
The gonado-somatic index and description of different
gonad maturity stages are summarized and presented in
Table 3. In general, the highest IGvalue was recorded dur-
ing February–March and July–August. A consistent pat-
tern of spawning of C. carpio was also found during
July–August when spawning of Indian major carps (Catla
catla,Labeo rohita, and Cirrhinus mrigala) occur. The
key indicators of spawning activity were the presence of
ripe, mature, and spent female C. carpio during rainy as
well as spring seasons.
Trophic spectra of 173 examined specimens of C. car-
pio revealed that there was similarity in the ingested food
at different locations. Similar types of algae and plant
Invasive common carp in the Ganga River 13
AI (%) =
n(k) × 100
N
r=∑xy – nxy
√[(∑x2– nx2) (∑y2– ny2)]
Singh et al.
14
Table 1
Fish species of the Ganga River
Species Family Habitat Length [cm] Status
Ailia coila Schilbeidae pelagic 18–30 Vu
Bagarius bagarius Sisoridae benthopelagic 39–89 Vu
Chitala chitala Notopteridae demersal 48–69 En
Gudusia chapra Clupeidae pelagic 12–20 LR-Ic
Notopterus notopterus Notopteridae demersal 28–74 LRnt
Puntius conchonius Cyprinidae benthopelagic 12–14 LRnt
Setipinna phasa Engraulidae pelagic 23–40 LRnt
Silonia silondia Schilbeidae demersal 58–68 LRnt
Sperata aor Bagridae demersal 63–78 NE
Sperata seenghala Bagridae demersal 39–65 NE
Tenualosa ilisha Clupeidae pelagic 28–74 En
Xenentodon cancila Belonidae pelagic 26–40 LRnt
Catla catla Cyprinidae benthopelagic 32–56 LRnt
Labeo rohita Cyprinidae benthopelagic 21–46 LRnt
Labeo bata Cyprinidae benthopelagic 14–28 LRnt
Labeo calbasu Cyprinidae demersal 28–38 LRnt
Cirrhinus mrigala Cyprinidae benthopelagic 14–42 LRnt
Cirrhinus reba Cyprinidae benthopelagic 12–14 Vu
Puntius sarana Cyprinidae benthopelagic 18–21 Vu
Pangasius pangasius Pangasiidae pelagic 58–92 En
Gonialosa manmina Clupeidae pelagic 12–14 LRnt
Clupisoma garua Schilbeidae pelagic 16–36 Vu
Mystus cavasius Bagridae demersal 26–39 LRnt
Rita rita Bagridae demersal 32–56 LRnt
Johnius coitor Sciaenidae demersal 12–18 LRnt
Glossogobius giuris Gobidae benthopelagic 14–22 LRnt
Mastacembelus armatus Mastacembelidae pelagic 21–32 LRnt
Anabas testudineus Anabantidae pelagic 14–18 LRnt
Salmophasia bacaila Cyprinidae benthopelagic 16–18 LRnt
Wallago attu Schilbeidae benthopelagic 56–126 LRnt
F
En = threatened; LRnt = lower risk near threatened; Vu = vulnerable; LT-lc lower risk least concern (on the basis of the
report of the Conservation Assessment Workshop held at NBFGR, Lucknow during 1997 and duly modified where neces-
sary: Ponniah and Sarkar 2000).
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0
10
20
30
40
50
60
Allahabad Varanasi Mirzapur Unnao Kanpur
AI %
C.carpio O.niloticus r value
Length − Weight regression [r]
Fig. 2. Abundance index and length–weight regression of Cyprinus carpio in the Ganga River
remains were found to be the major food items in com-
mon. The analyzed gut contents were Eichhornia (9.8%),
Pistia (11.6%), Nymphaea (8.5%), annelids worms
(7.8%), algae (20.2%), mud and detritus (14.8%) (Fig. 4).
The calculated diet breadth ranged from 0.82% to 0.91%,
food richness ranged from12 to 16, and gut repletion
index (GRI%) was 100% respectively (Fig. 5).
DISCUSSION
Exotic fish introductions have been reported to impact
the fish biodiversity and have provided significant warn-
ings of the various effects on environment posing threats
to the community trophic structure disrupting biological
integrity (Casal 2006, De Silva et al. 2006, García-
-Berthou 2007, Rowe 2007, Lakra et al. 2008). It has
also been realized that the nature and extent of such
changes being complex remains unpredictable. Exotic
species may become invasive and are capable of: spread-
ing exotic diseases, decreasing biodiversity through
competition, predation and habitat degradation, genetic
deterioration of wild populations through hybridization
and gene introgression in short or long course of time
(Casal 2006, Singh and Lakra 2006, García-Berthou 2007,
Lakra et al. 2008).
Invasive common carp in the Ganga River 15
Table 2
Important fish species and their contribution in commercial fishery of the Ganga River
Fish group Fish species
Length
range
[mm]
Weight
range
[kg]
Catch
contribution
[%] range
Indian major carps Catla catla, Cirrhinus mrigala, Labeo rohita, 200–550 0.4–8 5–10
Minor carps Labeo calbasu, L. bata, Cirrhinus reba,Puntius sophore,
P. conchonius
90–250 0.15–1.5 5–7
Catfishes Sperata aor, S. seenghala, Wallago attu, Channa punctata,
C. marulia, Mystus cavasius, Bagarius bagarius, Rita rita,
Clupisoma garua, Ailia coila, Notopterus notopterus
260–780 0.6–2 10–12
Miscellaneous Gonialosa manmina, Salmophasia bacaila, Glossogobius
giuris, Johnius coitor, Mastacembelus armatus,
Anabas testudineus
36–98 0.023–0.034 10–15
Exotic fishes Cyprinus carpio 70–690 0.025–8.5 12.2–45.5
Oreochromis niloticus 18–270 0.003–0.97 12.7–19.5
Aristichthys nobilis 0.39–18 stray catch
Ctenopharyngodon idella 0.55–7.9 stray catch
Hypophthalmichthys molitrix 0.45–9.5 stray catch
Clarias gariepinus 0.28–2.3 stray catch
S
0
500
1000
1500
2000
2500
2004 2008
Av. Annual Catch [tons]
Exotics Local
115.80%
24.56%
Fig. 3. Increased occurrence of exotic fishes in the Ganga River over the years (2004–2008)
Common carp was introduced into India during 1939
and 1957 (Froese and Pauly 2004, Singh and Lakra 2006)
for aquaculture purpose and it contributes more than
7.17% in total inland fish production (Dey et al. 2005).
The utilization of C. carpio gradually expanded for
enhancing reservoir fishery production (Suguan 1995,
Sugunan 2000) and it was then introduced into reservoirs
and lakes. After the expansion of the use of C. carpio for
enhancement of aquaculture production, its occasional
occurrences were later reported from open waters gravi-
tating Jhelum, Mahanadi, and Yamuna rivers (Singh and
Lakra 2006, Singh et al. 2008a). However, its occurrence
in the fishery of the Ganga River has been observed for
the first time and there is no other report. The local fishes
of the Ganga River were subjected to the threats of pollu-
tion by sewage and industrial wastes, deforestation,
excessive use of fertilizers, pesticides, and water develop-
ment programmes (Rao 2001, Sarkar and Bain 2006,
Singh and Singh 2008). Consequently, the catches of local
fish species were adversely affected (Lakra et al. 2009)
but invasion of exotic C. carpio and tilapia in the fishery
of the Ganga River has been found to aggravate the threats
to the indigenous fish diversity including environmental
problem (Gopal and Zutshi 1998, Rao 2001, Das 2007,
Khanna et al. 2007, Singh et al. 2008b).
Gonadal development of C. carpio has been reported to
be continuous in females (Parameswaran et al. 1972) and
the results of the present study also provided first evidence
of wild spawning of common carp in the Ganga River
forming feral population. Since common carp, C. carpio, is
known to exhibit early sexual maturity, rapid colonization
and wide environmental tolerances (Koehn 2004,
Singh and Lakra 2006), these attributes have been consid-
ered to help this exotic fish to successfully invade into
new environment of the Ganga River. Results of this
study delineated increased abundance of C. carpio in the
fishery and the reproductive staging of the fish ascer-
tained the presence of all reproductive stages (1–6) in the
river-caught C. carpio. This confirmed that common carp
has now established itself in the Ganga River and the so
colonized fishes constituted the bulk of the catch.
Fishermen are desperate of getting mostly low value fish
like common carp and tilapia which sell in the market at
low price of Rs. 35–40 per kg whereas IMCs, the demand
fish cost Rs. 60–70 per kg.
Introduced common carp has been reported to impli-
cate environmental changes principally eutrophication
through an increase in turbidity and mobilization of nutri-
ents to the water column from the benthos through its habit
of rooting or digging in the bottom (Britton et al. 2007,
Singh et al.
16
Table 3
Macroscopic appearance, gonado-somatic index (IG) and the gonad maturity stage
(according to Nagelkerke and Sibbing 1996) of ovary of Cyprinus carpio of the Ganga River
Stage
No. Stage IGnDescription
1 Immature < 1 14 Ovaries thin, transparent, circular (0.5–1 cm diameter) in cross
section. Oocyte faintly visible upon rupture of tunica albuginea
2. Immature developing (early) 0.5–5 23 Ovaries opaque, granular and occupied less than a third of body
cavity. Oocyte small, green yellow
3. Immature developing (late) 5–20 45
Ovaries occupied less than two thirds of body cavity with
abundant blood capillaries and large opaque oocyte (C.1 mm).
Some oocyte appeared translucent
4. Ripe 15–30 21 Ovaries distinctly bulging and lobular in appearance.
They filled the body cavity. Oocyte large (>1 mm)
5. Spent 1–5 18
Body musculature was stretched and body cavity was fl accid.
Ovaries were small, bloodshot and granular with scattered
residual vitellogenic oocyte
6. Regressing 3–10 11
Ovaries difficult to stage but appeared blotchy with atretic
oocyte in all developmental stages. Oocytes were variable
in colour
9.8
11.6
8.5
7.8
20.2
14.8
Eichhornia Pistia Nymphea
Annelid worms Algae Mud & Detritus
Fig. 4. Major food items [%] in the gut of Cyprinus car-
pio from the Ganga River
Khanna et al. 2007, Rowe 2007). The invasion of com-
mon carp, Cyprinus carpio, in Australia has already been
reported to quickly spread and dominate fish communities
(Koehn 2004). Significant negative effects of common
carp on the piscine diversity have been reported (Lakra et
al. 2008, Ross et al. 2008). Common carp in India has
already been reported to cause sharp decline in the catch-
es of endemic schizothoracids (Singh and Lakra 2006,
Lakra et al. 2008). Due to introduction of common carp in
the lakes of Kumaon, the catches of schizothoracids was
found to drastically decline (Singh and Lakra 2006) and
the production of common carp increased since 1985
(Shyam Sunder 1998). In Manipur, it has escaped in Loktak
Lake and now contributing an important fishery replacing
the important local and endemic fish species particularly
Osteobrama belangeri (see Singh and Lakra 2006). The
declining trend of Indian major carps in the Ganga River
and increasing appearance of common carp in the fishery
is a warranting situation of biological invasion threaten-
ing ecological integrity. The problem of repopulating C.
carpio in degrading water of the river (Gopal and Sah
1993, Gopal and Zutshi 1998, Khanna et al. 2007) has
come up to conserve rich fish genetic resources of the
Ganga River before it faces a major alteration. This
would not only influence the human but might induce
either more adaptability of the biota living in it or might
cause damage to various species which would not be able
to adapt to such fast ongoing change. The adverse
impacts on the wild population due to common carp have
been assessed in the Ganga River and it is a big concern
to the conservation biologists. Its rapid spread and colo-
nization in the Ganga is understood to cause dramatic
ecological disruptions at the community and ecosystem
levels (Titus et al. 2004, Mabuchi et al. 2008). Adverse
impacts of C. carpio have been recorded across the
world, including North America (Britton et al. 2007),
Japan (Mabuchi et al. 2008), New Zealand (Rowe 2007),
and Australia (Koehn 2004). The results of this study
highlights that the common carp has established in the
Ganga River as a pest through naturally breeding popula-
tions which is now becoming the source for secondary
invasions at other places. Impacts of exotic fish in the
Ganga have been found to be mild at present but it may
cause habitat alteration, trophic structure alteration, and
hybridization in due course of time (De Silva et al. 2006,
García-Berthou 2007, Lakra et al. 2008). Gut content
analysis, the diet breadth, and the gut repetitive index
showed similar pattern at all the sampling stations. This
result indicated that ecological conditions in the Ganga
were homogenizing by the increasing population of com-
mon carp which could be a great threat to the ecological
integrity for this mighty river sustaining rich fish biodi-
versity. The gut content analysis delineated presence of
mainly plant material and algae of similar kind. Benthic
feeding by invasive common carp has been reported to
usually result in adverse impacts upon invaded ecosys-
tem with declines in submerged vegetation (Titus et al.
2004). Since degraded ecosystems are often more sus-
ceptible to successful invasion of exotic fish species,
other introduced exotic fishes may also find access and
then negatively impact the biodiversity cumulatively
(Singh and Lakra 2006, García-Berthou 2007, Lakra et
al. 2008). The present change in dynamics of the fishery
due to the burgeoning presence of common carp invites
Invasive common carp in the Ganga River 17
0
20
40
60
80
100
120
0
2
4
6
8
10
12
14
16
Allahabad Varanasi Mirzapur Unnao Kanpur
Diet breadth
No. of food items
Food richness Diet breath GRI %
Fig. 5. Trophic spectra of Cyprinus carpio in the Ganga River
attention to conserve rich indigenous germplasm facing
threats of shifting from their natural habitats.
ACKNOWLEDGEMENTS
Authors are grateful to Dr. S. Ayyappan, Director
General, Indian Council of Agricultural Research, New
Delhi for his kind support and encouragements for carry-
ing out this study. The help provided by the officers of the
Uttar Pradesh Fisheries Department particularly Dr.
Arvind Mishra, Assistant Director Fisheries, Varanasi is
thankfully acknowledged. The authors are also thankful to
Mrs. Reeta Chaturvedi, Technical Assistant (T-4),
NBFGR for providing help in the preparation of graphs
and charts of this manuscript. Thanks are also due to Mr.
Vishwanath Nishad, an active worker of fishermen socie-
ty of Allahabad for his help in arranging fishing and sam-
pling works.
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Received: 8 May 2009
Accepted: 19 November 2009
Published electronically: 25 June 2010
Invasive common carp in the Ganga River 19
