Limnologica 91 (2021) 125925

Contents lists available at ScienceDirect

Limnologica
journal homepage: www.elsevier.com/locate/limno

Influence of cage farming and environmental parameters on

spatio-temporal variability of fish assemblage structure in a tropical
reservoir of Peninsular India
Sajina A.M., U.K. Sarkar *, Canciyal J., B.K. Das, A. Saha, P. Mishal, Jesna P.K., M. Ramteke, A.
K. Das
ICAR-Central Inland Fisheries Research Institute, Barrackpore, Kolkata, 700120, India

A R T I C L E I N F O A B S T R A C T

Keywords: Fish assemblage structure in Palair reservoir, a medium tropical reservoir along the river Paleru, a tributary of
Fish diversity river Krishna in Southern India, was studied along the spatial gradient of the impoundment. The abundance and
Physico-chemical parameters assemblage structure of wild fish aggregated around the fish cage units installed in the reservoir were assessed
Enclosure culture
and compared with other sites. Seasonal sampling was carried out and fish community structure in terms of
Impact
Conservation
species composition and abundance, trophic guild, niche, tolerance, resilience and conservation status were
Sustainability analyzed. A total of 38 fish species were recorded wherein the family Cyprinidae dominated in the number of
species (15) followed by Cichlidae and Channidae (3 each). Margalef richness index (d), Pielou’s evenness index
(J’), Simpson’s index (1-λ) and Shannon index (H’) revealed significant variation across different zones. Species
richness was maximum in the Site1 (d = 4.44–5.12), whereas the abundance of individuals was maximum at
Site4 (H’ = 2.65–2.86) i.e. near cage in the lacustrine zone. The important species contributing to the dissimi­
larities among the zones were identified and percentage of their contribution was estimated using SIMPER
analysis. Trophic guild of fishes indicated the dominance of omnivorous species followed by carnivores, indi­
cating the heterotrophic phase of the reservoir. The spatial and seasonal variations in the fish assemblage
structure were tested applying statistical analyses such as PERMANOVA and nMDS. The results indicated a
positive impact of cage farming in supporting the wild fish fauna, influencing the large aggregations of fishes
around the cages. The temporal variability in the cage-associated fish assemblage was related to recruitment
periods of juveniles (e.g. E. maculates and E. suratensis in summer, and S. seenghala in monsoon seasons). The links
between fish assemblages and environmental parameters were explored through DISTILM and the deterministic
factors for fish abundance in the reservoir were phosphate, pH, dissolved Oxygen, total hardness and depth. The
study also indicated the impacts of cage culture with record of accidental escapes of farmed fish to the reservoir
system. The baseline information generated and recommendations formulated in the study are crucial for the
conservation of fish diversity, fisheries enhancement and management planning of tropical peninsular reservoirs.

1. Introduction productivity. Although the average annual productivity realized from

Indian reservoirs is 110 kg ha− 1 yr− 1 (Sarkar et al., 2018), the fish
Reservoirs are lentic or semi-lentic systems built by impounding the productivity potential of the system is very high, to a level of 500 kg
lotic systems such as rivers or streams. Though reservoirs are built for ha− 1 yr− 1from the small; 200 kg ha− 1 yr− 1 from the medium; and 100 kg
various purposes, including hydropower generation, flood control, ha− 1 yr− 1 from the large reservoirs with the adoption of fisheries
drinking water supply, irrigation, etc. they also contribute considerably enhancement practices (Sugunan, 2015; Das et al., 2021). It is well
to the inland fish production. Indian reservoirs, with a total estimated accepted that Indian reservoirs are still a sleeping giant with the pro­
area at about 3.5 million ha (Sarkar et al., 2018), are situated in the duction of fish way below their potential (Sugunan, 2020). Since marine
tropical region with high nutrient turnover favoring biogenic and coastal waters as well as rivers are approaching plateau in

* Corresponding author.
E-mail address: usarkar1@rediffmail.com (U.K. Sarkar).

https://doi.org/10.1016/j.limno.2021.125925
Received 31 May 2020; Received in revised form 23 August 2021; Accepted 6 September 2021
Available online 14 October 2021
0075-9511/© 2021 Elsevier GmbH. All rights reserved.
S. A.M. et al. Limnologica 91 (2021) 125925

production growth, the entire burden of producing additional fish for Indian reservoirs are subjected to fisheries enhancement through
meeting the national targets lies on aquaculture and reservoir fisheries. stocking as well as fish production through cage culture. Influence of
Cage culture, an intensive aquaculture production system within net these interventions on the native fauna as well as fish community dis­
enclosures, has received substantial attention of researchers, entrepre­ tributions are not explored and this study was a first of its kind to explore
neurs and policymakers in recent years as the increase in fish production the same. The study was conducted to explore the fish diversity, analyze
in net cages worldwide is contributing to meet the growing demand for the seasonal and spatial variability in fish assemblages, and investigate
animal protein to the growing world population. In the context of the influence of cage farming in the fish assemblage pattern in Palair, a
stagnant production from the marine sector and declining production of tropical medium reservoir systemin peninsular India. Though there are
inland capture fisheries, the efforts are in place to enhance aquaculture some preliminary studies on the diversity of the Palair reservoir
activities and fish production from reservoirs for meeting the increasing (Johnmohammad et al., 2015; Chandrasekhar and Jaiswal, 2015), the
fish demand in country. Considering India’s rich and varied open water spatio-temporal patterns in fish diversity as well as fish assemblage
resources like reservoirs, lakes and floodplain wetlands, enormous scope structure of the reservoir was not fully explored. In the present study, the
exists to increase production through enclosure culture, especially the major environmental parameters influencing the fish abundance and
cage culture. Cage culture in reservoirs is being looked upon as an op­ their distribution were also assessed. The unanticipated impacts of cage
portunity with great production potential in India (Sharma et al., 2016) culture, such as the accidental escape of farmed fish are also discussed.
and the culture of commercially important diversified species are found Based on the baseline information drawn from the study, a few recom­
to be useful for realization of water productivity, entrepreneurship and mendations were formulated for sustainable management of reservoirs
employment generation paving a way for the empowerment of fisherfolk exploited for fisheries development.
(Sarkar et al., 2018). Also, the oligotrophic nature of medium and large
reservoirs of the country offers ample scope for implementation of cage 2. Material and methods
culture technology for intensive fish production and almost all Indian
states have taken up cage farming in reservoirs, with varying levels of 2.1. Study area and sampling design
success.
The cage culture projects are capital-intensive and subject to many Palair reservoir, also called as Paleru reservoir is a medium reservoir
environmental risks. A few studies have indicated that there are envi­ located in the Khammam district of Telangana state in Southern India.
ronmental effects in native ecosystems due to cage farming, as these River Paleru is a tributary of the Krishna River which joins the main river
systems involve intensive rearing with high stocking rate, use of high in Krishna district in the state of Andhra Pradesh. Palair reservoir was
protein feed and use of non-native fishes. Some studies evaluated the constructed on the river at Paleru town, built by erstwhile Nizam Mir
impacts of cage culture systems in the surroundings (Buschmann et al., Osman Ali Khan for the irrigation of crop lands in 1929. The reservoir
2006; Forchino et al., 2011), especially the fish assemblages and most of also acts as a balancing reservoir to the left canal of the larger reservoir,
these studies were carried out in the coastal environment for sea cages Nagarjunasagar and it has a water spread area of 17.25 km2 (Chan­
(Boyra et al., 2004; Dempster et al., 2005; Valle et al., 2007; Riera et al., drasekhar, 2014) (Fig. 1). It is one of the heavily exploited medium
2017). In the case of sea cages, cage culture of fishes became an addi­ reservoirs in Telangana for various purposes such as drinking water
tional source of nutrients in the bay and such nutrients were the most supply, irrigation, hydropower generation, recreational boating and fish
critical factors contributing to differences in species abundance due to production. Culture-based fisheries management is followed for the fish
cage system (Challouf et al., 2017). Though there are a few studies production from this reservoir, with the annual stocking of seeds of In­
exploring the abundance of wild fish assemblages around fish cages in dian major carps, Catla catla, Labeo rohita and Cirrhinus mrigala, and
reservoirs (Nobile et al., 2018; Huang et al., 2020), no such reports are native prawns, Macrobrachium rosenbergii and M. malcolmsonii. During
available from tropical Indian reservoirs. the study year 2018, nine batteries of cage farming units were opera­
Fish assemblage structure of reservoirs shows great similarity to tional in the lacustrine zone of the reservoir; four GI cage batteries with
parent river in initial years and over the years it changes with conspic­ 16 cages each (5m × 5m × 4 m cage dimension) and five pontoon HDPE
uous decline in species richness through gradual removal of pre-existing cage batteries with 10 cages each (6m × 4m × 4 m cage dimension),
fluvial fish species and with increasing abundance of species with pre- with a total cage farming area of 0.28 ha. The land use pattern and other
adaptations to thrive in standing waters (Agostinho et al., 2016). This features of the catchment area near sampling sites are given in the
shifting pattern in fish diversity causes lower diversity in reservoirs, and supplementary Table S1.
ichthyofaunal monitoring surveys conducted in Indian reservoirs indi­ Fish diversity, assemblage structure and seasonal dynamics of fish
cate that most reservoirs contain fewer than 50 fish species (Sreekantha abundance were studied through stratified random sampling in the
and Ramchandra, 2005; Pawar, 2014; Lianthuamluaia et al., 2019), reservoir. The samplings were carried out in four different sites of the
irrespective of the very rich ichthyofauna in the parent river. Thus, the reservoir to study the spatial variation in fish assemblages and also to
pattern of fish assemblage in a reservoir varies with time due to expected explore the changes in assemblage due to cage culture in the system.
trophic depletion in subsequent years after filling. With properties of Sampling sites were chosen to cover the lotic (Site 1), transitional (Site
both lentic and lotic systems, spatial variation in fish species distribution 2) and lacustrine (Site 3 and Site 4) part of the reservoir. In the lacustrine
exists in reservoirs. In general, the upper part of a reservoir tends to have zone, two sites, one near the cage (Site 4, mentioned as cage site) and
riverine features, whereas the lower part has lacustrine characteristics one away from the cage (Site 3, mentioned as lacustrine) as control,
(Irz et al., 2002; Terra et al., 2010; Sanches et al., 2016). The evaluation were chosen to compare fish assemblage patterns due to cage system
of spatial variations in species diversity can provide vital information for (Fig. 1). Sampling was carried out seasonally covering pre-monsoon
assessing the impact of habitat on fish community structure, critical for (summer) in May, monsoon (rainy) in September, and post-monsoon
conservation of these resources (Sandhya et al., 2018). Hence, it is sig­ (winter) in December in the year 2018.
nificant to study the spatio-temporal patterns in fish diversity and the Experimental fishing was conducted for the sampling and it was
structure of fish assemblages of reservoirs, in the context of conservation made sure that uniform effort was used in all sampling stations in terms
and management perspectives. of gear and duration. Gill nets of four different mesh sizes (30 mm, 45
Several studies have been carried out on fish assemblage structure of mm, 90 mm and 115 mm stretched distance between opposite knots)
Indian reservoirs (Sugunan, 1995; Shahnawaz et al., 2010; Sarkar et al., were used in the sampling for duration of 12 h (overnight fishing). Cast
2018) and its variations in the spatio-temporal gradient (Sandhya et al., netting (25 mm) was also done with the help of local fishers. The fishes
2018; Lianthuamluaia et al., 2019), no work has so far been done on the were identified following identification keys given by Talwar and
impact of fisheries enhancement practices on the native fauna. Most Jhingran (1991) and Jayaram (2010). Eight physico-chemical

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S. A.M. et al. Limnologica 91 (2021) 125925

Fig. 1. Map of Palair reservoir, Telangana, India and the sampling sites [Site1- Lotic; site2- Transitional; site3- Lacustrine (away from cage); site4- Lacustrine
(cage site)].

parameters viz. water temperature, depth, pH, Dissolved Oxygen, as well for each site, as a percentage of total abundance (Mahajan and
transparency, electrical conductivity, total alkalinity and silicate were Fatima, 2017). SIMPER routine of Primer 7 software was run to break
analyzed (Table S2) from the water samples taken from each site down the pairwise dissimilarities between the sites. In order to reflect
following standard protocols (APHA, 2005). Secondary data and Fish­ the community differences among samples, non-metric multidimen­
Base (Froese and Pauly, 2019) were followed for categorizing species sional scaling (nMDS) plots were constructed for the Bray-Curtis simi­
based on the trophic guild, niche of occurrence, tolerance and resilience larities of the square root transformed species abundance data, using
and IUCN red data book (IUCN, 2020) for enlisting the conservation Primer 7. PERMANOVA analysis was also carried out with the resem­
status. blance matrix, keeping site and season as factors.
To explore how the environmental parameters control or influence
the fish faunal distribution, DISTLM (distance based linear modeling)
2.2. Statistical analysis procedure was carried out with fish abundance data as resemblance
matrix and the eight water quality parameters as predictor variables
The fish abundance data were analyzed for assessing the species using PERMANOVA + add on of Primer7 software. The water quality
richness, species dominance or evenness and species diversity using data was normalized, whereas fish abundance data were square rooted
Primer 7 software. Various indices, viz. Margalef richness index (d), before converting to resemblance matrix.
Pielou’s evenness index (J’), Simpson’s index (1-λ) and Shannon index
(H’) were estimated for each site. Species wise relative abundance was
estimated from species abundance data pooled for all sites and seasons,

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3. Results species in the reservoir were Parambassis ranga (20.71 %), Chanda nama
(10.75 %) and S. bacaila (8.52 %). The relative abundance of exotic
3.1. Fish diversity and major species tilapia was quite high (3.2 %). Among the stocked IMCs, L. rohita was
more abundant (3.09 %), followed by C. catla (1.96 %) and C. mrigala
A total of 38 species were reported from the reservoir, belonging to (1.77 %), respectively. The site-wise relative abundance indicated var­
15 families under 9 orders (Table 1). Family Cyprinidae, with a repre­ iations in abundance of different species (Fig. 2). The major species were
sentation of 15 species (39.5 %), was the dominant family in the O. cotio, S. bacaila and E. maculatus in the Site1; Rhinomugil corsula, L.
reservoir. The three species of Indian major carps, C. catla, L. rohita and rohita and Glossogobius giuris in Site2, P. ranga, O. niloticus and O. cotio in
C. mrigala, which were regularly stocked in the reservoir as part of the Site 3; and P. ranga, C. nama, and S. bacaila in the cage site, i.e. Site4
culture-based fisheries management dominated among the Cyprinids (Fig. 2).
along with species such as Salmophasia bacaila, Osteobrama cotio cotio,
Amblypharyngodon mola, Puntius spp, etc. The next dominant family was
3.2. Fish assemblage structure and classification of fishes
Cichlidae and the three representing species were Etroplus suratensis, the
green chromide, E. maculates the orange chromide and the exotic Nile
The categorization fish assemblage of the reservoir into different
Tilapia, Oreochromis niloticus. With three species representatives, air-
guilds based on the trophic structure, niche, tolerance, resilience, and
breathing fish family Channidae was also significant in the reservoir
conservation status are listed in Table 1. Trophic guild analysis of the
fish fauna. Major three catfish families in the reservoir were Bagridae,
fish assemblage indicated that omnivorous feeders (25 species) domi­
Siluridae and Schilbeidae, and the abundant catfish species were Sperata
nated among the reservoir ichthyofauna, followed by carnivores (13
seenghala, Ompok bimaculatus, Wallago attu and Mystus cavasius. Among
species) (Table 1). Considering the niche occupied, benthopelagic or
the recorded fishes, two are exotic species, viz. Tilapia (O. niloticus) and
column dwellers were the major group (25 species), followed by
Pangas (Pangasianodon hypophthalmus).
demersal or benthic dwellers (8 species), whereas 5 species were pelagic
Based on relative abundance estimated using species abundance data
or surface dwellers. Based on species vulnerability, 23 species of the
pooled for all sites and seasons, the most abundant (by number) three
reservoir fish fauna were falling in the medium tolerant category, 7 in

Table 1
Trophic guild, dwelling habit (niche), utilization, resilience and conservation status of the fish fauna of Palair reservoir.
Species Family Trophic Dwelling Tolerance Population doubling Conservation status Exploitation
Guild habit level time (IUCN) category

Amblypharyngodon mola Cyprinidae O BP MT L LC FD

Aplocheilus panchax Aplocheilidae O BP MT L LC FG
Catla catla Cyprinidae O BP I M LC FD
Chanda nama Ambassidae C BP MT L LC FD, OR
Channa marulius Channidae C BP I M LC FD
Channa punctata Channidae C BP MT M LC FD
Channa striata Channidae C BP MT M LC FD
Cirrhinus mrigala Cyprinidae O D MT H LC FD
Esomus danricus Cyprinidae O BP MT L LC OR
Etroplus maculates Cichlidae O BP MT H LC FD
Etroplus suratensis Cichlidae O BP MT H LC FD
Glossogobius giuris Gobiidae C BP MT H LC FD
Hyporhamphus limbatus Hemiramphidae C P MT L LC FD
Hyporhamphus xanthopterus Hemiramphidae C P MT H VU FD
Labeo rohita Cyprinidae O BP I M LC FD
Labeo rohita (Jayanti strain) Cyprinidae O BP I M LC FD
Laubuka laubuca Cyprinidae O P MT H LC OR
Macrognathus pancalus Mastacembelidae O BP MT H LC OR, FD
Mastacembelus armatus Mastacembelidae O D MT M LC FD
Mystus cavasius Bagridae C D MT M LC FD
Nandus nandus Nandidae C BP MT H LC OR, FD
Notopterus notopterus Notopteridae O D I M LC FD
Ompok bimaculatus Siluiridae O D MT H NT FD
Oreochromis niloticus Cichlidae O BP MT M LC FD
Osteobrama cotio cotio Cyprinidae O BP MT M LC FD
Pangasianodon Schilbeidae C BP I L EN* FD
hypophthalmus
Rasbora daniconius Cyprinidae O BP T H LC OR
Pethia ticto Cyprinidae O BP T H LC OR
Parambassis ranga Ambassidae O D T H LC OR
Puntius amphibius Cyprinidae O BP T M DD OR, FD
Puntius chola Cyprinidae O BP T H LC OR, FD
Puntius sophore Cyprinidae O BP T H LC OR, FD
Rhinomugil corsula Mugilidae O P MT M LC FD
Salmophasia bacaila Cyprinidae O BP T M LC FD
Salmophasi auntrahi Cyprinidae O BP T M LC FD
Sperata seenghala Bagridae C D I L LC FD
Systomus sarana Cyprinidae O BP MT M LC FD
Wallago attu Siluridae C D I H NT FD
Xenentodon cancila Belonidae C P MT H LC FD

O-Omnivorous; C-carnivorous, BP-benthopelagic, D-demersal, P-pelagic, I-intolerant; MT-medium tolerant; T-tolerant; L-low; M-medium; H-high; EN- endangered;
DD- data deficient; LC-least concern; NT-near threatened; VU- vulnerable; FD- food; FG- forage; OR-ornamental.
*
endangered in the native ecosystems only.
(Source: Froese and Pauly, 2019; IUCN, 2020).

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S. A.M. et al. Limnologica 91 (2021) 125925

Fig. 2. Relative abundance of major fish species in Palair reservoir in each sampling site.

intolerant and 8 in highly tolerant categories. The population doubling S. bacaila (Table 3). The nMDS plot indicated differentiation of sites
time (PDT) using FishBase estimates was taken as a measure of species based on fish abundance with a 2-dimensional stress value of 0.05
resilience. It was observed that 16 species were high resilient with low (Fig. 4). The spatial variation in fish assemblages were also supported by
PDT, 15 species were medium resilient and 7 species were having low PERMANOVA (with site as a factor), which indicated significant dif­
resilience, with a longer PDT. The conservation status of the species ferences in fish abundance among different sites (pseudo-F = 4.488 and
recorded was also analyzed, which showed that species like p < 0.001).
O. bimaculatus and W. attu fall under near threatened and Hyporhamphus
xanthopterus under vulnerable categories, as per IUCN Red Data Book 3.4. Seasonal variation in fish abundance
(IUCN, 2020). P. hypophthalmus, the species recorded as an accidental
escape from the cage units falls under the endangered category globally Species such as C. nama, P. ranga, and O. cotio cotio were abundant
considering its native population. Most fishes caught from the reservoir throughout the year in the reservoir. Many species showed seasonal
are utilized as food, whereas 10 species among the recorded have variation in their abundance such as dominance of E. maculates, E. sur­
ornamental value. atensis and S. bacaila in pre-monsoon, S. seenghala and P. ranga in
monsoon and tilapia and stocked IMCs, especially L. rohita in post-
3.3. Spatial distribution of fish diversity monsoon months (Table 2). There were seasonal variations in rich­
ness, evenness and diversity indices estimated for the study sites (Fig. 3),
The distribution of fish abundance varied considerably along the yet the trend was more or less the same for different sites. The species
spatial gradient (Table 2), and the spatial variation in fish assemblages richness was maximum at the Site1 in the post-monsoon season (d =
was evident from the values of various richness and diversity indices 5.13). The species richness near the cage site was also high in the post-
(Fig. 3). From the values of Margalef Index (d) for different sites, species monsoon season (d = 4.68) and it was reduced greatly in monsoon
richness was highest for site1 (d = 4.44–5.12) with the presence of 36 season (d = 3.46). In the monsoon season, the difference in the evenness
species, followed by site4 (d = 3.45–4.67) with 32 species and one index was less among the sampling sites than pre-monsoon and post-
improved strain. Considering the evenness, site2 was more even with monsoon seasons. The Simpson’s and Shannon diversity indices did
Pielou’s index (J’) value indicating a very even relative abundance of not show significant seasonal variation. ANOVA of seasonal diversity
the different species in the Site2 (J’ = 0.84− 0.97). The two diversity indices data of sites didn’t show significant variation (p > 0.05) among
indices, Simpson’s (1-λ) and Shannon (H’), which take account of both the seasons (Table S3). PERMANOVA of resemblance matrix of fish
richness and abundance were having high values for site1&4 followed abundance data (with season as a factor) did not indicate significant
by site3 and least for site2. With only 8 species recorded, site2 had seasonal variation in fish assemblages (pseudo-F = 0.528 and p =
lowest fish diversity. ANOVA revealed significant difference in diversity 0.881).
indices (Table S3) among the sites (p < 0.05), however evenness index
didn’t show significant variation (p > 0.05) among the sites although it 3.5. Effect of cage system on fish assemblages
was found highest for site2. A richer abundance of fishes was observed
near the cage system in the lacustrine zone indicating the influence of The two lacustrine sites, the cage site (site 4) and the control site
cage in the spatial density of fishes in the reservoir system. (away from cage, site 3), varied in number of species recorded (with 32
The SIMPER analysis indicated that similar species contributed to the species and one improved strain, and 29 species respectively) (Table 2)
variation of fish assemblage of cage site from other study sites and the as well as in diversity and abundance indices, clearly depicting the fact
differences in fish assemblage structure were mainly driven by small that cage systems strongly influence the surrounding fish assemblage
sized perchlets, barbs and carplets such as C. nama, P. ranga, A. mola and structure. Though the species diversity recorded from the two lacustrine

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S. A.M. et al. Limnologica 91 (2021) 125925

Table 2
Fish species composition and abundance in Palair reservoir.
Reservoir sites Season
Fish Species
Site 1 Site 2 Site 3 Site 4 Pre-M M Post-M

Amblypharyngodon mola + – – +++ ++ ++ ++

Aplocheilus panchax + – – – + – +
Catla catla ++ + + ++ + + ++
Chanda nama ++ – + +++ +++ +++ ++
Channa marulius + – + ++ + + +
Channa punctata + – – + + + +
Channa striata – – + – – + –
Cirrhinus mrigala ++ – + ++ ++ + +
Esomus danricus + – + + + + +
Etroplus maculates ++ – + +++ +++ ++ +
Etroplus suratensis ++ – + ++ ++ ++ +
Glossogobius giuris ++ + + ++ + ++ ++
Hyporhamphus limbatus + – + – + – –
Hyporhamphus xanthopterus + – + + + – +
Labeo rohita ++ + + ++ ++ ++ ++
Labeo rohita (Jayanti strain)** – – – + – – +
Laubuka laubuca + – – – + – +
Macrognathus pancalus – – + ++ + + +
Mastacembelus armatus + + + – + + +
Mystus cavasius + – + ++ + ++ +
Nandus nandus + – + + + – +
Notopterus notopterus + – – – – + –
Ompok bimaculatus + – – + + + +
Oreochromis niloticus* + + ++ ++ + ++ ++
Osteobrama cotio cotio + – ++ +++ ++ ++ +++
Pangasionodon hypophthalmus + – – + – – +
Rasbora daniconius + – + + + + +
Pethia ticto + – + ++ ++ + +
Parambassis ranga ++ – ++ ++++ +++ +++ ++++
Puntius amphibius + – + + + – +
Puntius chola + – + ++ ++ + +
Puntius sophore + – + +++ +++ ++ +
Rhinomugil corsula + + + + ++ + +
Salmophasia bacaila ++ – + ++++ ++++ ++ ++
Salmophasia auntrahi ++ – – ++ ++ + +
Sperata seenghala ++ – + +++ + +++ ++
Systomus sarana + – + +++ + ++ ++
Wallago attu + + – + + + +
Xenentodon cancila + + + ++ ++ ++ +

+ less than 10, ++, 10–50, +++ 50–100, ++++ more than 100.
*
Exotic species.
**
selectively bred strain.

sites were more or less similar, there were considerable differences in dissolved oxygen level was high in the reservoir with an average of 7 mg
their abundance with high numbers of each species in the samples l− 1 (5.6–10.7 mg l− 1 range). The pH of the reservoir water was slightly
collected from the near cage site. The Shannon index value was as high high (9.08–10.25 range) and the average total alkalinity was 101.1
as 2.87 for the cage site, whereas it varied from 1.86 to 2.55 for the mgl− 1 (Table S2). The average Electrical Conductivity was 471.5μScm-1
control site (Fig. 3). The exotic species Pangas (P. hypophthalmus) and and silicate content was 8.96 mgl− 1. Major environmental factors which
Jayanti rohu, the genetically improved strain of L. rohita, recorded from got influence over fish abundance and their distribution were explored
the reservoir during sampling are assumed to be accidental escapes from for the reservoir using the DISTLM method. The DISTLM model using the
the cages as these two were cultured in the cages. One specimen of forward selection procedure and R2 criterion explained up to 51.5 % of
P. hypophthalmus (41.5 cm TL) was caught from the lotic zone and a few the variation in the fish assemblages of the reservoir, and attributed the
more specimens near the cage site. Three specimens of Jayanti rohu variation to the 8 environmental variables. Phosphate contributed the
were caught from the surroundings of the cage using a cast net. highest percentage (21.5 %), followed by pH (15.2 %), total hardness
From the PERMANOVA results for pair-wise comparisons among (11.4 %), depth (9.3 %), alkalinity (7.6 %), air temperature (6.5 %),
different sites (Table 4), it is clear that the fish assemblages of cage site electrical conductivity (6.1 %), chlorinity (6.5 %), silicate (6.5 %) and
are much different from Site3 (p = 0.097) as well as Site2 (p = 0.090), water temperature (3.3 %). The dbRDA plot emphasized the vectors that
whereas it is more alike to the fish assemblage structure of Site1 (p = correspond to the variables selected in the DISTLM models (Fig. 5). The
0.102). The nMDS plot also indicated similarity of fish assemblage length and direction of the vectors indicate strength and direction of the
structure of Site1 and Site4 (Fig. 4). relationship. There is decent agreement evident between dbRDA and the
nMDS plots (Figs. 4 and 5), indicating a good fit for the DISTLM models.

3.6. Environmental factors influencing the fish abundance 4. Discussion

The water temperature varied greatly in the reservoir with season Palair reservoir was filled almost a century ago, and such a long span
from 23.7 ◦ C to 32.4 ◦ C. The average water depth of the reservoir was 6 after reservoir closure is widely considered for the stabilization of fish
m (3.05–9.5 m range), with average transparency of 1 m; the lowest assemblages in a reservoir. Though there are evidence of stabilization of
transparency (0.6 m) at site 4 and highest (1.25 m) at site 2. The

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Fig. 3. Spatial and seasonal variation of diversity indices in Palair reservoir [(a) Margalef Richness Index; (b) Pielou’s Evenness Index; (c) Simpson’s Diversity Index;
(d) Shannon-Diversity Index]. Error bars represent ± SE.

Table 3 Table 4
SIMPER analysis results for fish species contributing most to dissimilarities be­ PERMANOVA results for pair-wise comparisons among different sites.
tween cage site and other sites (cumulative limit of 50 %). Groups t P (perm)
Lotic (Site1) vs. Cage site Transitional (Site2) vs. Lacustrine (Site3) vs.
Lotic, Transitional 2.5636 0.102
(Site4) Cage site (Site4) Cage site (Site4)
Lotic, Lacustrine 1.0291 0.499
Species DP% Species DP% Species DP% Lotic, Cage site 1.5394 0.105
Transitional, Lacustrine 2.1195 0.094
C. nama 7.64 P. ranga 10.10 C. nama 9.64 Transitional, Cage site 3.3413 0.090
P. ranga 6.77 C. nama 9.39 P. ranga 7.86 Lacustrine, Cage site 1.6391 0.097
A. mola 6.19 A. mola 6.03 A. mola 7.22
S. bacaila 6.18 S. bacaila 4.97 S. bacaila 5.24
S. sarana 5.15 E. maculates 4.63 P. sophore 4.63
P. sophore 5.02 S. sarana 4.60 S. sarana 4.61
O. cotio cotio 3.94 P. sophore 4.21 M. cavasius 4.28
M. cavasius 3.85 M. cavasius 4.14 S. untrahi 4.25
S. untrahi 3.82 O. cotio cotio 3.80 S. seenghala 4.00
E. maculates 3.74

DP%- = percentage contribution to total dissimilarity.

Fig. 5. Plot of DISTLM analysis using fish abundance and environmental pa­
rameters of Palair reservoir.

fish community structure between 15 and 40 years after reservoir filling

(Mol et al., 2007; Orsi and Britton, 2014), there is no consensus
Fig. 4. Clustering dendrogram of sampling sites based on Bray- regarding the time for stabilization of fish assemblages in reservoirs
Curtis similarity. (Petrere, 1996). Dam operation patterns and water level fluctuations

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S. A.M. et al. Limnologica 91 (2021) 125925

cause constant perturbations in reservoirs affecting its fish assemblage high longevity (k-strategists) (Agostinho et al., 2016).
stabilization process. Palair is a heavily exploited system for fish pro­ The fish diversity and abundance showed distinct patterns along the
duction, where fish stocking and heavy fishing are carried out as part of spatial gradient, as indicated by richness, evenness and diversity indices,
culture-based reservoir management, practiced as in most small and and also the SIMPER and NMDS analysis. The fish assemblage analysis
medium reservoirs of India. River Paleru, the parent river of the reser­ indicated that all the sites were recorded with a greater number of
voir is one of the tributaries of Krishna river system, which is very rich in species (76.3–94.7 % of the total species recorded) compared to the
fish fauna (David, 1963; Jayaram, 1995). The state of Telangana, situ­ transitional zone which supported only 21 % of the total fish diversity.
ated on the Deccan Plateau, drained by major rivers such as Godavari Although abundance was less, the lotic zone of reservoir harbored much
and Krishna, and many minor rivers, also has many lakes and reservoirs diversity. The rich diversity in the lotic zone was observed in other
as inland fisheries resources. Srivastava et al. (2017) has reported 166 tropical large reservoirs of Brazil (Agostinho et al., 2007; Araújo et al.,
species of fishes from the inland waters of Telangana, a state with rich 2013) and also in large Indian reservoirs (Sandhya et al., 2018; Lian­
native fish fauna and where high fish production is targeted and ach­ thuamluaia et al., 2019), which may be accounted to similarities in flow
ieved through pond aquaculture and fisheries enhancement in reser­ with the parent river, the lower depth, and connectivity. This study also
voirs. The present work with 38 species is the highest diversity reported, indicated that even in medium reservoirs, the upper reaches are capable
Palair reservoir contributes almost 23 % of the total state fish diversity of sustaining higher richness of lotic fish species, probably due to their
of Telangana. The native fish faunal diversity and assemblage structure similarity with natural habitats and longer littoral area. The transitional
of Palair reservoir were less studied (Johnmohammad et al., 2015; zone, being ecotone of both lotic and lentic environments tends to
Chandrasekhar and Jaiswal, 2015), particularly immediately after harbor rich species in reservoirs as reported in many studies (Sandhya
filling and succeeding stages. The fish species reported from other res­ et al., 2018; Lianthuamluaia et al., 2019), but in case of Palair reservoir,
ervoirs of Telangana are 30 species from Koilsagar (Laxmappa et al., the trend was not followed, with lowest species diversity and abundance
2014), 64 species from Lower Manair Dam (Rao, 2014), 31 species from were reported in the transitional zone. Unlike in other reservoirs, there
Wyra reservoir (Rao et al., 2019), and 38 species from Udayasamudram was no macrophyte infestation in the transitional zone of this reservoir,
reservoir (Shyamsundar et al., 2017). Family Cyprinidae dominated in which may also account for the less diverse transitional zone. The
all these reservoirs, as in the case of Palair reservoir. The reservoir also sampling site for the zone was in the middle of the reservoir, far away
harbors exotic fishes like Tilapia, O. niloticus, with great abundance, from the littoral area, which may be a reason for the poor record of
which is a concern as the species may pose a threat to other indigenous species from the zone. Pelicice et al. (2008) explored macrophyte
fishes, especially the native cichlid species, E. suratensis and biomass as an interesting predictor of fish density and richness in
E. maculatus. The fishermen reported that the catch of both native neotropical reservoirs, through their observations on macrophytes
chromide species reduced due to the infestation of Tilapia in the reser­ playing important role influencing fish distribution. The very sparse
voir. Apart from fishes, two species of freshwater prawns, M. rosenbergii macrophyte vegetation might be a reason for low species richness and
and M. malcolmsoni, were also abundant in the reservoir, which were fish abundance in Palair reservoir due to non-availability of microhab­
also being stocked regularly to replenish the native stocks for a rich itats for the fishes to dwell. The presence of aquatic macrophytes in
prawn fishery. manageable quantity provides stability to reservoir ecosystem as they
The fish assemblage structure indicated massive proliferations of purify water and maintain the water quality parameters and keeps the
small-sized, non-migratory species (viz. P. ranga, C. nama, S. bacaila, S. environment relatively healthy and sustainable in controlled growth
untrahi, O. cotio etc) in the studied reservoir, which have high repro­ situations (Thomaz and da Cunha, 2010; Sarkar et al., 2021).
ductive potential and short longevity (r-strategists) (Hasan et al., 2021; Taking account of the seasonal variation in fish abundance, higher
Froese and Pauly, 2019). This particular pattern is expected in a tropical diversity was recorded in post-monsoon season, yet the diversity indices
reservoir after achieving the fish community stabilization, similar to the were more or less similar for the other two seasons. Various species
observations of Agostinho et al. (2016) in Brazilian reservoirs. The showed marked variation in their abundance with respect to the season.
species recorded are mostly having pre-adaptations to thrive in lentic The results indicate high temporal variability in the cage-associated fish
waters, with lower dependence of fluvial waters. Only a few species with assemblage, which may be related to recruitment periods for juveniles
potamodromous nature were reported, and they included the Indian and specific preferences by other species for summer or monsoon pe­
major carps, mainly stocked for fisheries enhancement. Most species riods. The summer season was marked with the dominance of native
reported from the reservoir falls under the SIF (small indigenous fishes) cichlids, smaller barbs and glassy perchlets. Limited connectivity with
category, and are mostly self-recruiting populations with a greater role the parent river in the summer season may be a reason for the less
in the nutritional security of fish-eating populations of the state. The abundance of large sized fishes in pre-monsoon sampling. During
fishery of SIFs such as A. mola, and Puntius spp, and many other species monsoon, schilbeid catfish S. seenghala dominated in the reservoir
with ornamental value need special attention to ensure their sustainable fishery. The increased abundance of such large catfishes in monsoon is
utilization. mainly through the improved river connectivity and also through
Trophic guild analysis of the fish assemblage indicated that omniv­ floodwaters during the season. As the reservoir is stocked for fisheries
orous species dominated among the reservoir fish fauna, indicating the enhancement during monsoon season with subsequent closure on fish­
heterotrophic phase of reservoir. Piscivorous species like W. attu were ing activities, post-monsoon sampling yielded more Indian major carps
found in good numbers and large size (upto 105.9 cm weighing more and also exotic Tilapia along with other native fishes. Less fishing
than 7 kg). The poor representation or absence of herbivorous guild pressure exerted during fishing closure might have boosted the prolific
might be due to lack of macrophytes in the reservoir unlike most tropical breeding of Tilapia, increasing their abundance. Temporal variation in
reservoirs. It may also be attributed to shifting abundance to omnivores fish assemblage structure was documented in many tropical reservoirs
and carnivores in the heterotrophic phase. The omnivores, with the (Okada et al., 2005; Lianthuamluaia et al., 2019).
advantage of feeding plasticity, tend to thrive easily even in impaired The study explored spatial variation in fish assemblages indicating
ecosystems. The dominance of fishes of medium tolerance indicates a changes in assemblage to cage culture in the reservoir system. Shannon
slightly to moderately impaired ecosystem. Similarly, the absence of diversity index indicated that the site near cage exhibited the highest
wild fishes with high PDT or low resilience also indicates the complete diversity compared to other zones in terms of abundance and domi­
adaptation of fish community structure to the lentic system with the nance. With results providing evidence of local aggregation in the
massive proliferation of small-sized, sedentary species, which are r- associated fish assemblages around the cage units, the study indicates
strategists. It has been well documented that fish species most affected that the cage influences on the surrounding natural ecosystem and its
by the damming or impoundments are large-sized, migratory species of fish communities. It signifies the role of cage as food chain support to the

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S. A.M. et al. Limnologica 91 (2021) 125925

fish community directly, through excess feed and organic wastes, and water temperature and transparency explained the seasonal and spatial
indirectly, by enhancing plankton productivity and has greater impli­ changes in fish abundance in the wetland of Cross River, Nigeria (Offem
cations in the spatial density of fishes in the reservoir system. The et al., 2009). The DISTLM analysis pointed out that assemblage and
attraction exerted on native reservoir fish fauna by the food supplied but occurrence of fishes in Palair reservoir were greatly influenced by a
not consumed by fishes in cages may be the reason for large aggregations combination of water quality parameters.
around cages. Demétrio et al. (2012) studied the effects of cage farming Palair reservoir is endowed with many ecological services besides
in the diet of wild ichthyofauna in a neotropical reservoir. Apart from functioning for purposes of drinking water supply, irrigation, hydro­
the influence of feed, thigmotropism in fish (the attraction to a solid power generation, and tourism activities (recreational boating) and
object) (Ibrahim et al., 1996) may also account for the large aggrega­ being a balancing reservoir to the large Nagarjunasagar reservoir. The
tions of fishes around cages and cage acting as FADs (Fish Aggregating reservoir acts as a germplasm reserve for the native fauna of Paleru, the
Devices) in reservoirs. These aggregations make the native fish fauna reservoir’s parent river, being a seasonal stream, which almost dries up
vulnerable to overfishing and predation, as no control overfishing op­ in peak summer. As a fishing hub to the nearby fishing communities, the
erations are being implemented in the reservoir system. Dempster et al. reservoir directly gives employment to more than 1200 fishers (the
(2005) suggested prohibiting fishing of large planktivorous species in members of primary corporative society looking after fisheries in the
coastal waters with cages to fully harness their ability to consume lost reservoir). With rich prawn and fish catch, it exclusively supports two
feed and assimilate nutrients for ameliorating benthic impacts. Similar adjacent fish markets (Palair and Nayakalgudam), where most vendors
to this, Riera et al. (2017) observed that the development of cage culture are women, and the distant Suryapet market partially shows the socio-
units might include their positive effects on wild fish aggregates, with a economic importance of the reservoir. Recently initiated cage farming
“buffer” fish-ban zone to protect fish stocks from the fishermen. Cage activities have brought in new opportunities for optimizing fish pro­
culture practices in reservoirs result in high fish catches as fish cages duction and developing new skills among fishers and entrepreneurs to
attract a diverse variety of wild fish, leading to increased fishing pres­ enhance their earnings. Following the national guidelines for cage
sure in the vicinity of cage farms as shown in the study by Huang et al. farming (NFDB, 2016), the carrying capacity of the reservoir can be up
(2020) in a Chinese reservoir. During the study, it was observed that to 500 cages and currently the operations are well below the limits. A
native murrels (Channa spp) were being farmed in few cages, and small huge increase in cage installations may be restricted as a precautionary
fishes caught by cast netting from the cage surroundings were chopped approach for the sustainability of the ecosystem. The artificial fish feeds
and given as feed to the farmed murrels. This practice is very looming to supplied in cages in more than optimal quantity often leads to eutro­
the indigenous fish fauna if it is done on a large scale. Hence, it is phication in reservoirs, with impacts on the chemical and physical
imperative to implement some fishing regulations in reservoirs so that quality parameters of water and sediments. Cage culture in reservoirs in
the commercial capture of fish around cage farms should be limited to a sustainable manner can contribute to global efforts for achieving Zero
protect the indigenous fish resources in reservoirs. Hunger, the second Sustainable Development Goal (SDG) through better
Accidental escapes of caged fishes are perceived as a major threat to use of biodiversity and can contribute to more nutritious diets, enhanced
wild fish populations and such escapes are largely caused by technical livelihoods for farming communities, and more resilient and sustainable
and operational failures of cagestructures or while changing the nets of farming systems.
cages, which is a routine maintenance practice in cage culture. Such This research is a starting point for future studies to gather infor­
escapes have been reported for many species presently cultured around mation from several medium and large reservoirs, where cage farming
the world, including Atlantic salmon, Atlantic cod, sea bream, sea bass, has already been initiated and expanded (Sharma et al., 2016; Sarkar
rainbow trout, Arctic charr, halibut etc. (Soto et al., 2001; Naylor et al., et al., 2018; Das et al., 2021) for seeking broader patterns that can apply
2005; Gillanders and Joyce, 2005; Moe et al., 2007; Toledo Guedes et al., to other similar environments in a larger scale. As the study was a first of
2009). Though the species P. hypopthalmus is a very popular candidate its kind effort to explore the influence of interventions like cage culture
species for cage farming many South Asian and South East Asian and culture-based fisheries on the native fauna as well as fish assem­
countries, it is an exotic species for India and its implications on native blage structure; specific recommendations were formulated based on the
fauna need to be considered. Another reported escape of Jayanti strain findings and observations for the scientific management of the tropical
of L. rohita is also to be taken seriously as it is a selectively bred strain for reservoirs exploited for fisheries enhancement and development.
aquaculture.
The environmental and water quality parameters in the reservoir • Regulation of fishing activities around the cage units installed in
showed that the reservoir is favorable for fish production. Chan­ reservoirs, to prevent overfishing and depletion of indigenous fish
drasekhar (2014) studied the limnological attributes of this reservoir fauna
and categorized it as a slightly polluted oligotrophic system. While • Strict preventive measures and biosecurity protocols to be followed
exploring the environmental drivers of fish spatial distribution, links for avoiding accidental escapes of farmed fishes (especially exotic
between fish assemblages and some environmental parameters were and genetically modified strains) from enclosure culture systems to
conspicuous from the DISTILM analysis between species distribution the reservoirs
and abundance and environmental variables. The DISTLM model indi­ • Periodic monitoring of water quality parameters and trophic status
cated that phosphate, pH, Dissolved Oxygen, total hardness and depth in reservoirs to be done around the cages for risk perception on
are the deterministic factors for fish abundance in the reservoir. nutrient loading
The key deterministic parameters influencing fish abundance in • Demarcation of hotspot areas in the fluvial riverine zone as conser­
Palair reservoir are phosphate, pH, Dissolved Oxygen, total hardness vation sites for maintaining biodiversity
and depth. The physico-chemical variables like temperature, DO, con­ • Impact of exotics on native fauna to be analyzed with ecosystem-
ductivity, pH, transparency, ammonia and alkalinity have been identi­ based modeling
fied as important factors in structuring sites and fish assemblages in • Fishing regulations in peak breeding season (during monsoon sea­
other tropical water bodies (Dubey et al., 2012; Sarkar and Bain, 2007; son) for continuous recruitment of self-recruiting native fish fauna
Tongnunui and Beamish, 2009; Wu et al., 2011). For freshwater fish • Maintaining macrophytes in a portion of reservoirs, to support native
communities, pH can be a major determinant of which species will be fauna as feeding ground and refuge to escape from predators
present because species vary widely in their tolerance of acidity (Greig • Sensitizing the key stakeholders (local fishers and cage fish farmers)
et al., 2010; Mills et al., 2000). In a tropical habitat in small rivers in of reservoirs on sustainable utilization of fisheries resources
eastern Thailand, a study showed that fish species richness was posi­
tively related to dissolved oxygen (Tongnunui and Beamish, 2009). The

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5. Conclusion Agostinho, A.A., Gomes, L.C., Santos, N.C.L., Ortegaa, J.C.G., Pelicice, F.M., 2016. Fish
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eries development. More in-depth and systematic studies on the impacts Chandrasekhar, S.V.A., 2014. Limnological variations of two Krishna river tributaries in
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CRediT authorship contribution statement
Central Inland Fisheries Research Institute, Kolkata, India.
David, A., 1963. Studies on fish and fisheries of the Godavary and the Krishna river
Sajina A. M.: Investigation, Formal analysis, Writing – original draft, systems-Part-1. Proc. Acad. Sci. India Sect. B 33 (2), 263–286.
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view & editing, B. K. Das: Funding acquisition, Supervision, A. Saha: Dempster, T., Fernandez-Jover, D., Sanchez-Jerez, P., Tuya, F., Bayle-Sempere, J.T.,
Investigation (environmental parameters), Mishal, P.: Investigation, Boyra, A., Haroun, R.J., 2005. Vertical variability of wild fish assemblages around
sea-cage fish farms: implications for management. Mar. Ecol. Progr. Ser. 304, 15–29.
Writing – review & editing, Jesna P. K.: Investigation (environmental https://doi.org/10.3354/meps304015.
parameters), M. Ramteke: Investigation (experimental fishing), A. K. Dubey, V.K., Sarkar, U.K., Pandey, A., Sani, R., Lakra, W.S., 2012. The influence of
Das: Investigation (experimental fishing, socio-economic data habitat on the spatial variation in fish assemblage composition in an unimpacted
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Funding information ecosystem in Alghero Bay (Sardinia, Italy) using AMBI and M-AMBI. Ecol. Indic. 11,
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Froese, R., Pauly, D., 2019. FishBase. World Wide Web Electronic Publication. www.
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kingfish via natural elemental signatures in otoliths. Mar. Freshw. Res. 56, 693–704.
State and ICAR-CIFRI during 2018− 2020’ financially supported by Greig, H.S., Niyogi, D.K., Hogsden, K.L., Jellyman, P.G., Harding, J.S., 2010. Heavy
Department of Fisheries, Govt. of Telangana. metals: confounding factors in the response of New Zealand freshwater fish
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Declaration of Competing Interest Hasan, M.R., Hossain, M.Y., Mawa, Z., Tanjin, S., Rahman, M.A., Sarkar, U.K.,
Ohtomi, J., 2021. Evaluating the size at sexual maturity for 20 fish species
(Actinopterygii) in wetland (Gajner Beel) ecosystem, north-western Bangladesh
The authors declare that they have no known competing financia­ through multi-model approach: a key for sound management. Acta Ichthyol. Piscat.
linterestsor personal relationships that could have appeared to influence 51, 29.
the work reported in this paper. Huang, G., Wang, Q., Yuan, T., Xiong, M., Liu, J., Li, Z., De Silva, S.S., 2020. Combined
effects of fish cage culture and increased fishing pressure on wild fish assemblages in
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