Species Abundance and Environmental Association of Nemacheilidae in South-Central Bhutan

Abstract

Nemacheilids are freshwater fishes distributed mainly in the South–central regions of Bhutan and environmental variables seems to have significant effect on their distribution, abundance, and diversity.
However, existing knowledge and information about nemacheilid’s association with its environment is
limited in Bhutan. This study aimed to assess nemacheilid’s abundance and determine its association
with environmental variables in the South–central Bhutan. The study was conducted in the three major
river basins; Punatsangchhu, Mangdechhu and Amochhu, which comprises of Dagana, Sarpang, Tsirang,
Samtse and Trongsa district. The data were collected from each stream using systematic random sampling, with samples collected at 100 m intervals spanning up to 500 m long. A total of 56 plots were surveyed from which nemacheilids were found in 22 plots. Eleven species were identified in three genera.
The mean relative abundance of Schistura beavani was the highest in Dagana (9.5), Paracanthocobitis cf.
botia in Sarpang (18.8), and S. devdevi in Tsirang (35.0) and Samtse (15.3). The lowest mean relative
abundance of P. cf. abutwebi was in Dagana (3.3), Aborichthys sp.2 in Sarpang (6.8), S. scaturigina in
Tsirang (5.0) and Aborichthys sp.4 in Samtse (2.1). No nemacheilids were found in Trongsa. The canonical correspondence analysis (CCA) showed a significant association between species abundance and 11
environmental variables (p = 0.01, Monte Carlo test with permutation of 999). Elevation and temperature
were the most influential variables followed by total hardness, electrical conductivity, turbidity, pH, total
dissolved solids, salinity, ammonia, dissolved oxygen and chloride with lesser importance. It is recommended to explore additional variables, sites and anthropogenic activities to further elucidate the dynamics of nemacheilids abundance and formulate effective conservation strategies.
Keywords: Abundance, Bhutan, CCA, environmental variables, Nemacheilidae

Full text

BJNRD (2024), 11(1): 34-47
Bhutan Journal of Natural Resources & Development
Open Access
www.bjnrd.org ISSN 2409–2797 (Print)
ISSN 2409–5273 (Online)
DOI: https://doi.org/10.17102/cnr.2024.94
34
BJNRD (2024), 11(1): 34-47
1College of Natural Resources, Royal University of Bhutan
*Corresponding author: karmalodhenwangmo@gmail.com
Received: May 9, 2024
Accepted: June 28, 2024
Published online: June 30, 2024
Editor: Ugyen Dorji and Nedup Dorji
Species Abundance and Environmental Association of Nemacheilidae in South-Central
Bhutan
Karma Lodhen Wangmo1, Dhan Bdr Gurung1, Karma Wangchuk1, Ugyen Dorji1, Laxmi
Sagar1, Rinchen Dorji1 and Rupesh Subedi1
Abstract
Nemacheilids are freshwater fishes distributed mainly in the South–central regions of Bhutan and envi-
ronmental variables seems to have significant effect on their distribution, abundance, and diversity.
However, existing knowledge and information about nemacheilid’s association with its environment is
limited in Bhutan. This study aimed to assess nemacheilid’s abundance and determine its association
with environmental variables in the South–central Bhutan. The study was conducted in the three major
river basins; Punatsangchhu, Mangdechhu and Amochhu, which comprises of Dagana, Sarpang, Tsirang,
Samtse and Trongsa district. The data were collected from each stream using systematic random sam-
pling, with samples collected at 100 m intervals spanning up to 500 m long. A total of 56 plots were sur-
veyed from which nemacheilids were found in 22 plots. Eleven species were identified in three genera.
The mean relative abundance of Schistura beavani was the highest in Dagana (9.5), Paracanthocobitis cf.
botia in Sarpang (18.8), and S. devdevi in Tsirang (35.0) and Samtse (15.3). The lowest mean relative
abundance of P. cf. abutwebi was in Dagana (3.3), Aborichthys sp.2 in Sarpang (6.8), S. scaturigina in
Tsirang (5.0) and Aborichthys sp.4 in Samtse (2.1). No nemacheilids were found in Trongsa. The canon-
ical correspondence analysis (CCA) showed a significant association between species abundance and 11
environmental variables (p = 0.01, Monte Carlo test with permutation of 999). Elevation and temperature
were the most influential variables followed by total hardness, electrical conductivity, turbidity, pH, total
dissolved solids, salinity, ammonia, dissolved oxygen and chloride with lesser importance. It is recom-
mended to explore additional variables, sites and anthropogenic activities to further elucidate the dynam-
ics of nemacheilids abundance and formulate effective conservation strategies.
Keywords: Abundance, Bhuta n, CCA, en vir onment al var iables, Nemacheilida e
Article
Introduction
Interaction of environmental variables in land-
scapes with biotic factors can result in environ-
mental variations, which play a crucial role in
shaping the distribution pattern of freshwater
fishes within river ecosystem (Beamish and
Plongsesthee, 2015). Studies have shown that
environmental variables, along with other hab-
itat features, are significant contributors to-
wards species diversity and abundance
(Beamish et al., 2008; Suvarnaraksha et al.,
2012; Giacomazzo et al., 2023). Growth and
distribution of fish fauna is influenced by the
physico-chemical attributes of an ecosystem
(Tobor, 1992; Lawal et al., 2023; Roy and
Saikia, 2023) making it important to observe
their interaction with the biotic factors. Tem-

35 Lodhen et al., 2024
Species Abundance and Environmental Association...
B A
perature, dissolved oxygen (DO) and pH are
some of the commonly used physico-chemical
parameters to assess relation with species di-
versity and its abundance (Negi and Mamgain,
2013; Ghimire and Koju, 2021; Mariu et al.,
2023) beacause these parameters are funda-
mental for basic metabolic processes, growth
and reproduction, contributing as significant
factors in their survival (Abowei et al., 2010;
Haque et al., 2023).
Nemacheilid loaches are commonly found
in the fast flowing streams with occasional oc-
currences in various environments such as
large rivers and caves, exhibiting its highest
diversity in Southeast Asia, boasting approxi-
mately 260 described species (Kottelat, 2013;
2020). Ongoing study continues to unveil new
species and genera within this family with the
majority of these new species being document-
ed and described in works by Kottelat (2000,
2001, 2023) and Freyhof and Serov (2001).
Nemacheilidae species have been recorded in
various parts of Bhutan, particularly in the
warmer regions (Gurung and Thoni, 2015).
Nemacheilidae species are commonly trad-
ed as ornamental fishes particularly in North-
east India (Ganguly et al., 2018). However,
overexploitation of these ornamental fishes has
led to unsustainable practices in management
of such fishes (Dash et al., 2023). Although
ornamental fish farming is not widely practiced
in Bhutan, nemacheilids as ornamental fishes
could have significant future potential. The
potential ornamental fish trade might lead to
overexploitation in wild population and could
affect vulnerable Nemacheilidae species in
Bhutan. Additionally, the existing knowledge
and research on the ecological interaction of
nemacheilids in the country is limited, which
represent a significant gap in our understanding
of these species and their roles in freshwater
ecosystems. Therefore, this study focus to
study the association between environmental
variables and nemacheilids in order to guide in
understanding the fundamental elements of
nemacheilids’ ecological interaction, identify-
ing critical habitats, and assisting in formulat-
ing effective conservation strategies.
Materials and Method
Study area
The study area encompasses five districts of
the three major river basins (Punatsangchhu,
Mangdechhu and Amochhu basins). Amochhu
is a trans-boundary river which originates from
the Tibet (an autonomous region of China) and
flows through the western districts of Haa and
Samtse, ultimately flowing into India. Addi-
tionally, Bindu Khola was also explored in
Samtse which connects with Jaldhaka river,
originating from the southeastern Sikkim
(National Center for Hydrology and Metorolo-
gy [NCHM], 2020). Punatsangchhu originates
from Gasa which flows through Tsirang, Sar-
pang and Wangdue Phodrang districts and
drains into India (NCHM, 2017). Mangdechhu
is one of four major sub-basins of Manas basin
which originates near Gangkhar Puensum and
flows into Zhemgang via Trongsa district
(NCHM, 2017). Subtropical and warm broad-
leaved forests are predominant in the region
with the exception of Trongsa with elevation
ranging from 100 – 1000 m and 1000 – 2000 m
above sea level respectively (Department of
Forests & Park Services [DoFPS], 2022). Cool
broad-leaved forest is predominant in Trongsa.
Subtropical forests experience rainfall of 2,500
– 5,000 mm while warm broad-leaved forests
have rainfall of 2,300 – 4,000 mm (DoFPS,
2022). This region is generally characterized
by hot and humid summer and dry and cold
winter (DoFPS, 2022). Plots were sampled
following Gurung and Thoni (2015) where
Nemacheilidae fishes have been reported in
these river systems.
Sampling method
A simple random sampling was used in select-
ing rivers for each district. Considering the
confluence of each stream with the main rivers
as the starting point, sampling stretches of
about 500 m were considered for sampling. A
total of 56 plots (Dagana, 14 plots; Sarpang, 10

36
plots; Tsirang, 10 plots; Samtse, 8 plots;
Trongsa, 15 plots) were surveyed while inac-
cessible streams were not surveyed due to lack
of accessible routes to reach these locations.
Within the 500 m stretch, five plots were se-
lected with an interval of 100 m. Each selected
plot was 20 m long where the presence of
nemacheilids was recorded and collected.
Since the nemacheilids are cryptic in behavior,
samples were collected using electro fishing
device and temporary water diversion. The
captured fishes were released back in the water
after identification and enumeration of the spe-
cies. Species which could not be identified in
the field were fixed in 10% formalin and pre-
served in 70% ethanol for subsequent identifi-
cation. Prior to fixing, the specimens were eu-
thanized using 0.04% clove oil. Identification
keys and visuals provided in Jayaram (1981,
2010) and Gurung and Thoni (2015) were re-
ferred for fish identification. Unconfirmed
specimens were designated as ‘sp.1, sp.2 and
so on.
Environmental variables
Parameters that were measured on site includ-
ed pH, electrical conductivity (µS/cm), temper-
ature (°C), dissolved oxygen (ppm), and total
dissolved solids (mg/L) which were measured
by ProDSS multiparameter digital water quality
meter. Elevation (m) was recorded by Garmin
eTREX 20 (± <10m). Chloride, ammonia, and
total hardness were measured using methods
adopted by American Public Health Associa-
tion ([APHA], 2017). Salinity was calibrated
using salinity meter and turbidity by Nephelo-
metric method at the Soil Air and Water Test-
ing (SWAT) laboratory of the College of Natu-
ral Resources (CNR), Royal University of Bhu-
tan (RUB). Sampling was conducted during
autumn season from September to November,
2022.
Data analysis
Total relative abundances of each species for
each district were calculated using a conversion
factor obtained by dividing the total abundance
estimate of each species by the total number of
fish caught. Species diversity was calculated
using the Shannon diversity index (Shannon
and Weaver, 1949):
Figure 1. Map showing study plots in r espective distr icts with r iver s.
BJNRD (2024), 11(1): 34-47

37
Where H’ represents the diversity index, pi is
the proportion of each species in the sample
and ln pi is the natural logarithm of this pro-
portion. Smith and Wilson’s (1996) Evar was
used to calculate the species evenness as it is
one of the most appropriate evenness indices
for general use:
Where xs is the abundance of the sth species, S
is the number of species in the sample, and
arctan provides an angle in radians. Canonical
correspondence analysis (CCA) was used to
find the association between species abun-
dance and environmental variables using R
version 4.3.2. Plots which had no nemacheilid
species were removed from the analysis.
Results and Discussion
Species abundance and composition
The study recorded a total of 281 nemacheilid
individuals from 22 plots belonging to three
genera (Aborichthys Chaudhuri 1913,
Schistura McClelland 1838 and Paracan-
thocobitis Gr ant 2007) and 11 species
(Aborichthys elongatus Hora 1921, Paracan-
thocobitis cf. botia, Schistura beavani
(Günther 1868), Paracanthocobitis cf. abut-
webi, Aborichthys boutanensis (McClelland
1842), Schistura devdevi Hora 1935,
Schistura scaturigina McClelland 1839,
Aborichthys sp.1, Aborichthys sp.2, Aborich-
thys sp.3 and Aborichthys sp.4) (Table 1).
Earlier studies have recorded four genera of
nemacheilids from the family Nemacheilidae
(Gurung and Thoni, 2015). However, the ge-
nus Triplophysa Rendahl 1933 was not detect-
ed in the current study. It is exclusively found
at higher elevations (Wang et al., 2015) mak-
ing their presence very unlikely in lower-
altitude environments.
The plots from Dagana comprised of
Aborichthys elongatus, Paracanthocobitis cf.
botia, Schistura beavani, P. abutwebi, S. sca-
turigina and Aborichthys. sp.1. Of the 11 spe-
cies recorded in this study, most species were
present in Sarpang except Aborichthys sp.3
and Aborichthys sp.4. Tsirang plots had two
species (S. devdevi and S. scaturigina) while
Samtse plots had four species (A. elongatus,
S. devdevi, Aborichthys sp.3 and Aborichthys
sp.4). Varied comparative mean relative abun-
dances were examined in four districts where
S. beavani was more abundant in Dagana,
Paracanthocobitis cf. botia in Sarpang, and S.
devdevi in Tsirang and Samtse (Table 1). The
least mean relative abundant species were Par-
acanthocobitis cf. abutwebi in Dagana,
Aborichthys sp.2 in Sarpang, S. scaturigina in
Tsirang and Aborichthys sp.4 in Samtse. All
the 15 sampling plots from Trongsa did not
have nemacheilids, which could be attributed
to the presence of Salmo trutta Linnaeus 1758
(Brown trout), which is a predatory species.
Brown trout was commonly found in all the
15 sampling plots in Trongsa and this fish is
an invasive species (Jan et al., 2023; Lowe et
al., 2000) which might have predated on the
native aquatic species.
Incidence of occurrence
Nemacheilids were present in about 39% of
the 56 plots of the five districts (Table 3). In-
cidence of occurrence for A. elongatus was
the highest in Sarpang (60%) followed by Da-
gana (46%) and Samtse (25%). Occurrence of
Paracanthocobitis cf. botia was the highest in
Sarpang (60%) followed by Dagana (8%) and
were absent in other districts. Schistura
devdevi was the highest in Sarpang (40%) and
Tsirang (40%) followed by Samtse (25%).
Sarpang had the highest occurrence incidenc-
es of S. beavani (40%), S. devdevi (40%), S.
scaturigina (40%), Aborichthys sp.1 (40%)
and A borichthys sp.2 (40%). Likewise,
Aborichthys sp.3 and Aborichthys sp.4 oc-
curred in Samtse. A borichthys sp.2 were pre-
sent in Sarpang (40%). Studies in certain parts
Lodhen et al., 2024
Species Abundance and Environmental Association...

38
of India, Nepal, and Pakistan found Nemachei-
lidae to be the second most abundant fish fam-
ily following Cyprinidae (Hasan et al., 2015;
Khatri et al., 2020; Baidya, 2022). Changlu et
al. (2021) reported the presence of Aborich-
thys and Schistura species from Manas basin
which is a continuation of Mangdechhu and
other larger tributaries downstream. However,
no species from the family were found in
Trongsa in this study, which probably induces
that the species recorded are predominantly
found in the warm water region. This could
also be one of the reasons as to why nemachei-
lids were not observed in Trongsa due to cool-
er temperature range in comparison to other
districts included in this study.
Environmental variables
Environmental conditions varied significantly
among different districts. Mean turbidity was
highest (11.8 ± 16.0 NTU) in Dagana and low-
est in Sarpang (3.0 ± 1.3 NTU) (Figure 2). The
heavy rainfall was experienced during the time
of data collection in Dagana which probably
explains high water turbidity from the sample
(Korman et al., 2021).
The average chloride concentration was
the highest (70.6 ± 27.6 mg/L) in Dagana and
the lowest (35.2 ± 21.9 mg/L) in Trongsa.
Chloride was found to be on higher range in
Dagana and Tsirang as compared to other dis-
tricts of this study. Elevated levels of chloride
concentration can indicate that the river is pol-
luted, which can impact the physiological pro-
cesses of organisms (Pal and Chakraborty,
2017). However, the chloride concentration in
the study was significantly below the maxi-
Species
Dagana (13 plots) Sarpang (10 plots) Tsirang (10 plots) Samtse (8 plots)
Rang
e
Mean ±
SD
Rang
e
Mean ±
SD
Rang
e
Mean ±
SD
Rang
e Mean ± SD
A. elongates 0 –8 9.5 ± 16.4 0 – 3 12.6 ± 0 0 0 – 4 4.2 ± 8.3
P. cf. botia 0–5 4.8 ± 17.3 0 – 4 18.8 ± 0 0 0 0
S. beavani 0 – 18.6 ± 0 – 3 8.5 ± 11.2 0 0 0 0
P. cf. abutwebi 0 – 5 3.3 ± 7.0 0 – 5 11.9 ± 0 0 0 0
A. boutanensis 0 0 0 – 3 8.5 ± 10.0 0 0 0 0
S. devdevi 0 0 0 – 5 18.1 ± 0 – 5 35.0 ± 0 – 8 15.3 ± 31.9
S. scaturigina 0 – 5 3.8 ± 9.6 0 – 3 7.9 ± 10.8 0 – 2 5.0 ± 15.8 0 0
Aborichthys sp.1 0 – 6.1± 12.3 0 – 3 7.0 ± 10.0 0 0 0 0
Aborichthys sp.2 0 0 0– 3 6.8 ± 9.5 0 0 0 0
Aborichthys sp.3 0 0 0 0 0 0 0 – 5 3.5 ± 9.8
Aborichthys sp.4 0 0 0 0 0 0 0 – 3 2.1 ± 5.9
Table 1. Ra nge and m ean relative abundance of Nema cheilidae species in river s of Dagana,
Sarpang, Tsirang and Samtse. SD indicates the standard deviation of mean relative abundance.
mum permissible limit (below 250 mg/L) of
the World Health Organization ([WHO],
2022) indicating occurrence of safe environ-
ment for the fishes. However, the average
concentration of ammonia was highest (0.12 ±
0.05 mg/L) in Trongsa and lowest in Tsirang
(0.02 ± 0.01 mg/L). Beamish et al. (2008)
observed that loaches are rarely present when
ammonia levels exceed 0.05 mg/L. However,
in cases of low ambient condition of ammo-
nia, it has no significant influence on species
abundance (p = 0.12). In Trongsa, the average
ammonia concentration was high (>0.05 mg/
L) which can be attributed to visible anthropo-
BJNRD (2024), 11(1): 34-47

39
genic activities including hydropower dam
construction in the area (Alla and Liu, 2021).
The mean temperature was the highest in
Sarpang (25.8 ± 1.5°C) and the lowest in
Trongsa (11.5 ± 1.9°C). Temperature is
known to be a critical factor in managing spe-
cies diversity as it has direct affiliation with
the metabolism of the fishes (Oberdorff et al.,
1995). Nemacheilids were found in tempera-
tures ranging from 17.6-25.8°C similar to the
range observed in prior studies by Suvarna-
raksha et al. (2012) and Beamish and Plongs-
esthee (2015). The highest (8.5 ± 0.5) mean
pH was recorded in Trongsa and lowest (7.4 ±
0.3) in Dagana. Teleosts species can be found
in small but critical pH range from 4.0-5.0 or
up to 9.0-10.0 (Parra and Baldisserotto, 2007).
District S E H’
Dagana 6 0.59 1.46
Sarpang 9 0.95 2.15
Tsirang 2 0.54 0.39
Samtse 4 0.81 1.21
The pH measured was under suitable range
(7.3-9.9) supporting ideal water quality.
Salinity was the highest (86.7 ± 36.4 ppm)
in Sarpang and the lowest (15.9 ± 2.1ppm) in
Samtse. Salinity significantly influences the
growth and density of aquatic organism’s pop-
ulation (Jamabo, 2008). The increased salinity
reduces swimming activities such as searching
behavior, potentially disrupting the ecological
processes of their habitat (Leite et al., 2022).
Three plots in Dagana exhibited slightly high
levels of salinity which prompts further inves-
tigation into potential contributing factors,
particularly anthropogenic influences in the
surrounding vicinity. These elevated salinity
Table 2. Diversity indices for four districts for 11 species.
Note: S=Richness, E=Evenness, H’=Shannon’s
diversity index
levels may be indicative of various human ac-
tivities, which need in-depth examination to
identify specific sources and potential environ-
mental implications.
Decline in dissolved oxygen concentration
in rivers is mainly attributed to higher temper-
ature (Tongnunui et al., 2023). However, the
average dissolved oxygen concentration across
all districts was high, with Tsirang recording
the highest concentration (8.95 ± 0.6 ppm) and
lowest at Samtse (6.3 ± 1.4 ppm).
The mean electrical conductivity was the
highest in Sarpang (168.4 ± 69.6 µS/cm) and
the lowest in Samste (31.5 ± 4.6 µS/cm). The
highest mean total hardness was recorded in
Trongsa (236.8 ± 47.3 mg/L) and the lowest in
Samtse (49.7 ± 17.8 mg/L). Extreme levels of
hardness are known to have negative impacts
on the growth and embryos of fishes
(Swain et al., 2020). Although the
concentration of total hardness in
Trongsa is below the permissible
limit of 500 mg/L (WHO, 2022),
absence of nemacheilids from
Trongsa could suggest lower toler-
ance for total hardness.
The mean total dissolved solids
was the highest in Sarpang (77.2 ±
32.4 mg/L) and the lowest in Samtse
(14.1 ± 1.9 mg/L). Elevated concen-
trations of suspended particles in the rivers has
the potential to disrupt its natural ecological
water system (Adjovu et al., 2023) and hence,
previous studies have reported changes in total
dissolved solids to have negative effect on
fishes (Ostrand and Wilde, 2004; Mueller et
al., 2017). However, the levels of total dis-
solved solids from all sampling plots fall be-
low the permissible limit (500 mg/L)
(National Environment Commission [NEC],
2020) indicating favourable condition for
nemacheilids.
Elevation ranged from 109-2460 m with
the lowest at Dagana and the greatest at
Trongsa. However, nemacheilids were present
in elevation ranging from 109 m (Dagana) to
Lodhen et al., 2024
Species Abundance and Environmental Association...

40
1019 m (Samtse).
Diversity of nemacheilids
Of the 11 species recorded across four dis-
tricts, Sarpang (S = 9) and Dagana (S = 6) had
the largest number of species. Two species
were found in Tsirang and four species in
Samtse, however, no species were found in
Trongsa (Table 2). Species diversity was the
highest in Sarpang (H’ = 2.15) and the lowest
in Tsirang (H’ = 0.39) (Table 2). Tsirang rec-
orded only species from the genus Schistura
while Sarpang consisted species from all the
three genera.
Sarpang exhibited the highest evenness (E
= 0.95) while the lowest evenness score was
exhibited by Tsirang (E = 0.54) (Table 2).
High evenness value seems to suggest bal-
anced distribution of nemacheilids with mini-
mal dominant species. However, Tsirang and
Dagana exhibited low evenness score suggest-
ing imbalanced distribution of the species.
The uneven distribution of the species can be
attributed to the presence of dominant species
of Schistura devdevi in Tsirang and Schistura
beavani in Daga na. Additionally, variation in
physico-chemical parameters affects the water
Species
Incidence of occurrence %
Dagana
(N=13)
Sarpang
(N=10)
Tsirang
(N=10)
Samtse
(N=8)
Trongsa
(N=15) 56 plots
Aborichthys elongatus 46 60 0 25 0 25
Paracanthocobitis cf. botia 8 60 0 0 0 13
Schistura beavani 38 40 0 0 0 16
Paracanthocobitis cf. abut-
webi
23 50 0 0 0 14
Aborichthys boutanensis 0 50 0 0 0 9
Schistura devdevi 0 40 40 25 0 18
Schistura scaturigina 15 40 10 0 0 13
Aborichthys sp.1 23 40 0 0 0 13
Aborichhthys sp.2 0 40 0 0 0 7
Aborichthys sp.3 0 0 0 12.5 0 2
Aborichthys sp.4 0 0 0 12.5 0 2
Table 3. Incidence of occur r ence (% ) for each species for each distr ict s and over all plots.
quality, which in turn affects the distribution
patterns of fishes and other aquatic organisms
(Hasan et al., 2015). The average concentra-
tion of turbidity for Dagana (11.8 NTU) and
Tsirang (5.9 NTU) was slightly above the per-
missible limits of NEC, 2020 and WHO, 2022
which may have influenced the distribution of
the nemacheilids. Other factors such as com-
petition for resources, presence and absence of
predators, and human disturbances may also
have influenced their ecological structure re-
sulting in variation in their diversity and even-
ness.
Environmental association with nemacheilid
abundance
Canonical correspondence analysis (CCA) of
environmental parameters with the abundance
of nemacheilids significantly correlated with
11 environmental factors (p = 0.01, Monte
Carlo test with permutation of 999). Axis 1
and 2 of CCA analysis explains 25.7% and
15.3% of the variation of data, respectively.
Axis 1 was positively correlated to pH, chlo-
ride, and elevation (Table 4). Turbidity, elec-
trical conductivity, ammonia, and total hard-
ness correlated positively on second axis while
BJNRD (2024), 11(1): 34-47

41
temperature, dissolved oxygen, total dissolved
solids, and salinity illustrated negative gradi-
ent on Axis 1 (Figure 3). The CCA ordination
indicates the relative environmental preference
of the species. The measure of magnitude is
quantified by the length of the vector.
The ordination showed species distribu-
tion in three groups; group one included
Aborichthys elongatus, Paracanthocobitis cf.
abutwebi, Aborichthys sp.1, Schistura sca-
turigina and S. beavani, group two included S.
devdevi, Aborichthys sp.3 a nd Aborichthys
sp.4 and, group three included A . boutanensis,
Paracanthocobitis cf. botia and Aborichthys
sp.2. Habitat of species in group one, on aver-
age, was characterized by the highest turbidity,
electrical conductivity, total dissolved sol-
vents, salinity, chloride, ammonia, total hard-
ness, the lowest dissolved oxygen, and eleva-
tion. Group two species habitat, on average,
was characterized by highest temperature,
lowest turbidity, pH, dissolved oxygen, chlo-
ride, moderate electrical conductivity, total
dissolved solvents, salinity, ammonia, total
hardness, and elevation. Group three species
habitat, on average, had the highest elevation,
dissolved oxygen, and similar pH range as
Variables Axis 1 Axis 2
Turbidity (NTU) -0.108 0.352
pH 0.103 0.339
Temperature (°C) -0.732 -0.092
Electrical conductivity (µS/cm) -0.392 0.038
Dissolved oxygen (ppm) -0.286 -0.008
Total dissolved solids (mg/L) -0.335 -0.015
Salinity (ppm) -0.334 -0.015
Chloride (mg/L) 0.048 0.236
Ammonia (mg/L) -0.314 0.251
Total hardness (mg/L) -0.392 0.300
Elevation (m) 0.951 -0.186
Table 4. Canonical corr esp ondence analysis coefficients for environmental variables for 22
plots
group one habitat; lowest temper-
ature, electrical conductivity,
total dissolved solvents, salinity,
ammonia and total hardness, and
moderate chloride and turbidity.
The CCA biplot indicated
Aborichthys sp.4 to have strong
negative association with eleva-
tion while Aborichthys sp.1,
Schistura scaturigina and S.
beavani have opposite associa-
tion. S. scaturigina and S. beava-
ni had weak negative association
with total hardness and ammonia
and, to varying degrees, with tur-
bidity (Figure 3). The loaches in
Bhutan have been recorded mainly in the
warmer regions ranging from South to the cen-
tral region (Gurung and Thoni, 2015).
Beamish and Plongsesthee (2015) and
Tongnunui et al. (2016) conducted similar
studies where lower elevation had significance
in the species abundance and diversity indicat-
ing that loach species prefer warmer regions
with the exception of some genera not present
in this study. Absence of nemacheilid species
in Trongsa could be attributed to higher eleva-
tion and colder temperatures. However,
Changlu et al. (2021) have reported presence
of Schistura species in Manas basin which
suggests the need to explore the region during
different seasons. The absence of nemachei-
lids could also be attributed to the presence of
predators. Aborichthys sp.1 had weak negative
association with electrical conductivity, dis-
solved oxygen, total dissolved solids and sa-
linity. Similar studies by Dwivedi et al. (2016)
and Satpathy et al. (2021) corroborated with
the result of this study which suggests the spe-
cies to be more sensitive to low levels of elec-
trical conductivity and total dissolved solids.
A. boutanensis, Paracanthocobitis cf. botia
and Aborichthys sp.2. were negatively associ-
Lodhen et al., 2024
Species Abundance and Environmental Association...

42
ated with pH and chloride. This is corroborat-
ed in similar study by Rajbanshi et al. (2021)
for nemacheilids. Paracanthocobitis. cf. abut-
webi had high negative association with tem-
perature while S. devdevi had opposite associ-
ation. A. elongatus had weak association with
environmental variables suggesting its adapta-
bility to thrive in broad conditions.
BJNRD (2024), 11(1): 34-47

43
Figure 2. Average, sta ndar d deviation (SD) and r ange of 11 physico-chemical parameters for 56
Figure 3. Distr ibution of fish species with r esp ect to significant envir onment al variables acr oss
five districts of Bhutan.
Conclusion
Nemacheilidae species diversity and abun-
dance were found high mainly in the warmer
regions with lower elevation range. The ob-
served strong negative association with eleva-
tion observed in CCA in multiple groups un-
Lodhen et al., 2024
Species Abundance and Environmental Association...

44
derscores the influence of altitude on the dis-
tribution patterns of these species. The identi-
fied clusters, each representing a unique eco-
logical niche, contribute to our understanding
of the complex interactions between environ-
mental factors and fish species in the region.
Turbidity, ammonia, total hardness, electrical
conductivity, salinity, pH, chloride, and total
dissolved solids were of lesser but important
factors affecting species abundance. Specific
environmental parameters that serve as key
indicators for the abundance of nemacheilids
can provide information which is crucial for
monitoring and assessing the health of aquatic
ecosystems in Bhutan, guiding policymakers
and resource managers in their efforts to pre-
serve biodiversity. It is essential to
acknowledge the inherent complexity of eco-
logical systems, and factors beyond those con-
sidered in this study which may contribute to
Acknowledgement
We express our gratitude to Mr. Sonam Mok-
tan and Mr. Ugyen Tenzin for facilitating la-
boratory analysis. We would like to give spe-
cial thanks to Mr. Kinley Dorji and Ms. Tshe-
wang Zangmo for assisting us in making map
and the Royal Society for Protection of Nature
(RSPN) for assisting us in the field.
variations in species abundance. Due to the
elusive nature and habitat preferences of the
species, nemacheilids in Bhutan are not widely
distributed, which is a challenge in their col-
lection. Therefore, future research study
should explore additional study areas, and en-
vironmental variables not included in this
study, and employ more nuanced methodolo-
gies to further elucidate the intricate interac-
tions shaping the abundance dynamics of
nemacheilids.
References
Abowei, J. F. N., Davies, O. A. and Eli, A. (2010). Physicochemistry, morphology and abundance of fin fish of
Nkoro River, Niger Delta, Nigeria. International Journal of Pharma and Bio Sciences, 6(2):1-11.
Adjovu, G., Stephen, H., James, D. and Ahmad, S. (2023). Measurement of total dissolved solids and total sus-
pended solids in water systems: A Review of the Issues, Conventional, and Remote Sensing Techniques.
Remote Sensing, 15(14):1-43.
Alla, Y. M. K. and Liu, L. (2021). Impacts of dams on the environment: a review. International Journal of
Environment, Agriculture and Biotechnology, 6(1): 64-74.
American Public Health Association (APHA). 2017. Standard methods for the examination of water and
wastewater. American Waterworks Association, Washington D.C, United States of America.
Arunachalam, M. (2000). Assemblage structure of stream fishes in the Western Ghats
(India). Hydrobiologia, 430:1-31.
Baidya, S. K. D. (2022). Seasonal variations in Ichthyofaunal assemblage in relation to Physicochemical pa-
rameters, Phytoplankton assemblage and Habscore of the Chathe River. International Journal of Ecology
and Environmental Sciences, 48(4):463-483.
Beamish, F. W. H. and Plongsesthee, R. (2015). Species diversity, abundance and environmental associations
of loaches (Nemacheilidae and Balitoridae) in the central region of Thailand. Natural History Bulletin of
the Siam Society, 60(2):89-111.
Beamish, F. W. H., Sa‐Ardrit, P. and Cheevaporn, V. (2008). Habitat and abundance of Balitoridae in small
rivers of central Thailand. Journal of Fish Biology, 72(10):2467-2484
Beaufort, L. F. D. (1951). Zoogeography of the land and inland waters. William Clowes and Sons. London.
Dash, P., Gargotra, P. and Tandel, R. S. (2023). Ornamental Fisheries in Hindu Kush Himalayan Region.
In Fisheries and Aquaculture of the Temperate Himalayas, eds. P. K. Pandey, N. Pandey and M. S. Akh-
tar, pp. 151-171. Springer, Singapore.
Department of Forests and Park Services. (2022). Forest Types of B hutan. Ministry of Agriculture and Forests.
Dwivedi, A. C., Mishra, A. S., Mayank, P. and Tiwari, A. (2016). Persistence and structure of the fish assem-
blage from the Ganga river (Kanpur to Varanasi section), India. Journal of Geography and Natural Dis-
asters, 6(159):2167-0587.
BJNRD (2024), 11(1): 34-47

45
Freyhof, J. and Serov, D.V. (2001). Nemacheiline loaches from Central Vietnam with descriptions of a new
genus and 14 new species (Cypriniformes: Balitoridae). Ichthyological Exploration of Freshwaters, 12:
133-191.
Ghimire, S. and Koju, N. (2021). Fish diversity and its relationship with environmental variables in Kamala
River, Nepal. Biodiversitas Journal of Biological Diversity, 22(11):
4865-4871.
Giacomazzo, M., Bertolo, A., Brodeur, P. and Magnan, P. (2023). Relationship between submerged aquatic
vegetation, turbidity, and fish distribution in a large shallow fluvial lake. Environmental Biology of Fish-
es, 106(1):1-17.
Gurung, D. B. and Thoni, R. J. (2015). Fishes of Bhutan: A preliminary checklist. Centre for Rural Develop-
ment Studies, Punakha.
Habit, E., Belk, M., Victoriano, P. and Jaque, E. (2007). Spatio-temporal distribution patterns and conservation
of fish assemblages in a Chilean coastal river. Biodiversity and Conservation, 16:3179-3191.
Hasan, Z., Ullah, S., Rasheed, S. B., Kakar, A. and Ali, N. (2015). The Ichthyofaunal Diversity , Relative
Abundance , Physico Chemical Analysis and the Estimation of Biodiversity Index of River Panjkora Dis-
trict Dir (Lower), Khyber Pakhtunkhwa. The Journal of A nimal & Plant Sciences, 25:550-563.
Haque, S. A., Jaman, A. and Hasan, M. S. (2023). Environmental impacts on seasonal fish diversity in Jamuna
River, Bangladesh. Journal of Survey in Fisheries Sciences, 10(1):3019-3030.
Jamabo, N. A. (2008). Ecology of Tympanotonus fuscatus (Linnaeus, 1758) in the mangrove swamps of the
upper bonny river, Niger delta, Nigeria. PhD thesis, Rivers state university of science a nd technology,
Port Harcourt, Nigeria.
Jan, A., Arismendi, I., Giannico, G. and Flitcroft, R. (2023). Habitat overlap among native and introduced cold
-water fishes in the Himalayas. Scientific Reports, 13(1):1-12.
Jayaram, K. C. (1981). The Freshwater Fishes of India Pakistan, Bangladesh, Burma and Sri Lanka. Zoologi-
cal Survey of India, Calcutta.
Jayaram, K. C. (2010). The freshwater fishes of the Indian region (Rev. 2nd ed.). Narendra Publishing House,
Delhi.
Khatri, K., Jha, B. R., Gurung, S., Khadka, U. R., Pokharel, S., Adhikari, A. and Shreshta, A. K. (2020). Fish
Diversity and Distribution Status in Bheri and Babai River, Mid-Western, Nepal. Proceedings of Interna-
tional Conference on Natural Resources, Agriculture and Society in Changing Climate.
Korman, J., Yard, M. D., Dzul, M. C., Yackulic, C. B., Dodrill, M. J., Deemer, B. R. and Kennedy, T. A.
(2021). Changes in prey, turbidity, and competition reduce somatic growth and cause the collapse of a
fish population. Ecological Monographs, 91(1):e01427.
Kottelat, M. (2000). Diagnoses of a new genus and 64 new species of fishes from Laos (Teleostei: Cyprinidae,
Balitoridae, Bagridae, Syngnathidae, Chaudhuriidae and Tetraodontidae). Journal of South A sian Natural
History, 5:37-82.
Kottelat, M. (2001). Fishes of Laos. Wildlife Heritage. Trust Publications, Colombo.
Kottelat, M. (2013). The fishes of inland waters of Southeast Asia: a catalogue and core bibliography of the
fishes known to occur in freshwaters, mangroves and estuaries. Raffles Bulletin of Zoology, 27:1-663.
Kottelat, M. (2023). Nemacheilus pullus, a new species of loach from central Laos (Teleostei: Nemachei-
lidae). Raffles Bulletin of Zoology, 71:106–115.
Kottelat, M. and Grego, J. (2020). Kayahschistura lokalayensis, a new genus and species of cave fish from
Myanmar (Teleostei: Nemacheilidae). Raffles Bulletin of Zoology, 35:179-185.
Lawal, N., Abdullahi, S. A. and Abolude, D. S. (2023). Physicochemical Characteristics and Fish Abundance
and Diversity of Mairua Reservoir Water, Funtua, Katsina State, North-Western Nigeria. Journal of Ap-
plied Sciences and Environmental Management, 27(1):125-132.
Lodhen et al., 2024
Species Abundance and Environmental Association...

46
Leite, T., Branco, P., Ferreira, M. T. and Santos, J. M. (2022). Activity, boldness and schooling in freshwater
fish are affected by river salinization. Science of the Total Environment, 819:153046.
Lowe, S., Browne, M., Boudjelas, S. and De Poorter, M. (2000). 100 of the W orld’s Worst Invasive Alien Spe-
cies A selection from the Global Invasive Species Database. In The Invasive Species Specialist Gr oup
(ISSG) a specialist group of the Species Survival Commission (SSC) of the World Conservation Union
(IUCN).
Mariu, A., Chatha, A. M. M., Naz, S., Khan, M. F., Safdar, W. and Ashraf, I. (2023). Effect of Temperature,
pH, Salinity and Dissolved Oxygen on Fishes. Journal of Zoology and Systematics, 1(2):1-12.
Montoya, J. M. and Raffaelli, D. (2010). Climate change, biotic interactions and ecosystem ser-
vices. Philosophical transactions of the Royal Society of London. Series B, Biological sciences, 365
(1549):2013-2018.
Mueller, J. S., Grabowski, T. B., Brewer, S. K. and Worthington, T. A. (2017). Effects of temperature, total
dissolved solids, and total suspended solids on survival and development rate of larval Arkansas River
shiner. Journal of Fish and Wildlife Management, 8(1):79-88.
National Center for Hydrology and Meteorology. (2017). A nnual Report (July 2016-June 2017). Royal Gov-
ernment of Bhutan.
National Center for Hydrology and Metorology. (2019). Analysis of Historical Climate and Climate Projection
for Bhutan. Royal Government of Bhutan.
National Center for Hydrology and Metorology. (2020). Final Report on Installation of Interim Community
Flood Early Warning System at Amochhu, Phuentsholing. Royal Government of Bhutan.
National Environment Commission. (2020). ENVIRONMENTAL STANDARDS, Royal Government of Bhutan.
Negi, R. K. and Mamgain, S. (2013). Species diversity, abundance and distribution of fish community and
conservation status of Tons river of Uttarakhand State, India. Journal of Fisheries and Aquatic Science, 8
(5):617-626.
Oberdorff, T., Gue´gan J. F. and Hugueny B. (1995). Global scale patterns of fish species richness in rivers.
Ecography, 18:345-352.
Ostrand, K. G. and Wilde, G. R. (2004). Changes in Prairie Stream Fish Assemblages Restricted to Isolated
Streambed Pools. Transactions of the American Fisheries Society, 133(6):1329- 1338.
Ou, C., Montaña, C. G., Winemiller, K. O. and Conway, K. W. (2011). Schistura diminuta, a new miniature
loach from the Mekong River drainage of Cambodia (Teleostei: Nemacheilidae). Ichthyological Explora-
tion of Freshwaters, 22(3):193.
Pal, S. and Chakraborty, K. (2017). Different Aspects of Chloride in Freshwater: A Review. International
Journal of Current Trends in Science and Technology, 7(8):20295-20303.
Parra, J. E. G. and Baldisserotto, B. (2007). Effect of water pH and hardness on survival and growth of fresh-
water teleosts. In Baldisserotto, B., Mancer a, J.M., Kapoor, B.G.. (eds.), Fish osmoregulation. Science
Publishers, New Hampshire.
Rajbanshi, D., Limbu, H., Khadka, N., Kumar, P., Gurung, J. K. and Limbu, D. K. (2021). Fish community
structure along altitudinal gradients with relation to environmental variables in Ratuwa River of Eastern,
Nepal. Our Nature, 19(1).
Roy, S. and Saikia, S. K. (2023). Characterization of Some Physico-Chemical Parameters of Water Bodies
Inhabited by Small Indigenous Fish Species (SIFs): A Case Study. European Journal of Aquatic Scienc-
es, 2(3):1-7.
Satpathy, S., Sivakumar, K. and Johnson, J. A. (2021). Fish communities and associated habitat variables in
the upper Subansiri River of Arunachal Pradesh, eastern Himalaya, India. Journal of Threatened
Taxa, 13(1):17477-17486.
Shannon, C. and Wiener, W. (1949). The Mathematical Theory of Communication. University of Illinois
Press, Illinois, United States of America.
Smith, B. and Wilson, J. B. (1996). A consumer's guide to evenness indices. Oikos. 76:70-82.
Suvarnaraksha, A., Lek, S., Lek-Ang, S. and Jutagate, T. (2012). Fish diversity and assemblage patterns along
the longitudinal gradient of a tropical river in the Indo -Burma hotspot region (Ping-Wang River Basin,
BJNRD (2024), 11(1): 34-47

47
Thailand). Hydrobiologia, 694:153-169.
Swain, S., Sawant, P. B., Chadha, N. K., Chhandaprajnadarsini, E. M. and Katare, M. (2020). Significance of
water pH and hardness on fish biological processes: A review. International Journal of Chemical Studies,
8(4):830-837.
Tobor, J. G. (1992). Fin and shellfish of conservation interest in Nigeria. NIOMR Tech Paper No 79:1-23.
Tongnunui, S., Beamish, F. W. and Kongchaiya, C. (2016). Fish species, relative abundances and environmen-
tal associations in small rivers of the Mae Klong River basin in Thailand. Agriculture and Natural Re-
sources, 50(5):408-415.
Tongnunui, S., Beamish, F. W. H., Sooksawat, T., Wattanakornsiri, A., Chotwiwatthanakun, C., Supiwong,
W., Intacharoen, P. and Sudtongkong, C. (2023). Temporal Changes in Water Quality with Increasing
Ambient Temperatures Affect the Distribution and Relative Abundance of 10 Species of Balitorid Fishes
in Small Streams of Eastern Thailand. Water, 15(15):2791.
Wang, Y., Yang, L., Wu, B., Song, Z. and He, S. (2015). Transcriptome analysis of the plateau fish
(Triplophysa dalaica): Implications for adaptation to hypoxia in fishes. Gene, 565(2):211-220.
World Health Organization (2022). Guidelines for drinking‑water quality: fourth edition incorporating the first
and second addenda. Geneva.
Lodhen et al., 2024
Species Abundance and Environmental Association...