chapter- 5.0 threats - shodhgangashodhganga.inflibnet.ac.in/bitstream/10603/50880/16/16... ·...
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133
Chapter- 5.0 THREATS
Extensive surveys during the study period have identified the following factors as threats
to the chelonian fauna of the Kaziranga NP.
5.1 Freshwater turtles as Fishery bycatch:
Evidence of freshwater turtle catch or bycatch in the Kaziranga NP stretch of the
Brahmaputra River is available in few literatures. In the Brahmaputra River, Bishwanath
Ghatis a very busy fishing hub (Plate. P/T-1.A) with around 1000 fishers and their
families, depending on the fishes caught from the Brahmaputra River for their
livelihood.Similarly, the Mora Diffolu River (Plate. P/T-1.B) on the southern periphery
of the park is also heavily exploited for fishing and agricultural activities. Maximum
number of fishing activities were observed in Bishwanath ghat (mean and SD, 36.766
±13.38) followed by Laodubi- Kaziranga beat stretch of Mora Diffolu river and Dhanbari
of Brahmaputra River (Table. T/T-5).Nine species of hardshell and softshell freshwater
turtles were found to be affected by unregulated fishing activities in Bishwanath ghat
area during the study period.
Fishing Gears:
Various fishing gears like gill nets of varying length and mesh size, lift nets, cast nets,
bamboo mats, box type bamboo traps and line hooks were observed in the Brahmaputra
River (Bishwanath Ghat) and Mora Diffolu River. Majority of the gears were Gill nets
(73%) followed by lift nets, lift nets, cast nets, box traps and hooks (Fig. D/T-1). The gill
nets were of varying size in respect to length and mesh size. The longest net size ranges
between 0.5 to 2 km in length and 12-15 meter in width. The mesh size ranged between
1.5 cm to 10 cm, depending on the target species. The gill nets were generally placed for
overnight or day long for 12-24 hours in water but often kept permanently up to 7 days,
with daily monitoring by boat. The box type bamboo trap (locally called Khalaha) is a
bamboo made box of 1X1 meter size having one entry door for fishes. They were
generally placed in shallow water areas especially in side dried up channels with low
water current.
134
Fig. D/T-1: Fishing gears observed in Bishwanath ghat
Species Affected:
In the Brahmaputra River (Bishwanath Ghat) the following freshwater turtle species
from families, Trionychidae and Geoemydidae are recorded to be fishery bycatch.They
were- Nilssonia hurum, N. nigricans, N. gangeticus, Chitraindica, Pangshura
sylhetensis, P. tentoria, P. smithii, Geoclemys hamiltonii and Hardella thurjii.
The Mora Diffolu River was also heavily exploited for fishing activities. However the
bycatch rate is low here. An adult female Hardella thurjii individual was rescued from a
fishnet near Mihibeel in summer of 2008 and many individuals of Pangshura tentoria
were recorded during the study throughout the whole stretch of Mora Diffolu.
A total of 432 numbers of freshwater turtles were recorded during the study in
Bishwanath Ghat which was caught in different fishing gears, among which 16.67%
(n=72) bycatch were dead due to passive fishing techniques. Majority of the bycatch
comprised of juvenile individuals (Plate. P/T-2.A & B) of both hardshell and softshell
turtles including G. hamiltonii (32%), followed by Pangshura tentoria (29%)and P.
sylhetensis (16%), while Chitra indica was the least affected species (Fig. D/T-2).
Whereas, the gillnets constituted 87% of total freshwater turtle bycatches followed by
the cast nets and hooks while the lift nets were with zero turtle bycatch (Fig. D/T-3).
73%
4%
14%
5%4% Gill net
Cast net
Lift net
Box trap
Hooks
135
Plate: P/T-1
A & B: Fishing activities in Brahmaputra and Mora Diffolu River
A
B
136
Fig. D/T-2: Volume of turtle bycatch species in Bishwanath Ghat
Fig. D/T-3: Turtle bycatch volume in different gears
16%
29%
8%
32%
2%
4%2%
6%
1%
P. sylhetensis
P. tentoria
P. smithii
G. hamiltonii
H. thurjii
N. hurum
N. nigricans
N. gangeticus
C. indica
87%
2% 5%
6% Gill net
Lift net
Box trap
Hooks
Cast net
137
Juveniles and hatchlings of both softshell and hardshell turtles (Plate. P/T-2) as well as
small sized adult male and female of Pangshura genus were caught in the fishnets. The
freshwater turtle bycatch volume was maximum in the winter season, which constituted
around 50% of the total bycatches, followed by pre-monsoon season (23%). The bycatch
was considerably less during the monsoon (15%) and post monsoon (12%) seasons (Fig.
D/T-4). Around 85% of freshwater turtle bycatch mortality was recorded in the gill nets
alone followed by the line hooks and box traps, that constituted 13% and 2% mortalities
respectively, while, the lift nets and cast nets caused no bycatch mortality (Fig. D/T-5).
The mortality in gill nets was maximum during monsoon (67%) and post monsoon
(22%) period, while it was negligible in the winter and pre monsoon seasons (Fig. D/T-
6).
Fig. D/T-4: Season-wise turtle bycatch volume
23%
15%
12%
50%
pre monsoon
monsoon
post monsoon
winter
138
Fig. D/T-5: Turtle bycatch mortality in different gears
Fig. D/T-6: Season-wise Turtle bycatch mortality in gillnets
0
10
20
30
40
50
60
70
Gill net Lift net Box trap Hooks Cast net
C. indica N. gangeticus
N. nigricans N. hurum
H. thurjii G. hamiltonii
P. smithii P. tentoria
P. sylhetensis
Fishing gears
Nu
mb
ers
0
5
10
15
20
25
30
35
40
pre monsoon monsoon post monsoon winter
C. indica N. gangeticus
N. nigricans N. hurum
H. thurjii G. hamiltonii
P. smithii P. tentoria
P. sylhetensis
seasons
Nu
mb
ers
13
9
Tab
le.
T/T
-1:S
pec
ies
wis
e fr
esh
wat
er t
urt
le b
yca
tch
vo
lum
e in
dif
fere
nt
fish
ing g
ears
G
ill
net
Sa
mp
lin
g e
ffo
rt
1
2
3
4
5
6
7
8
9
10
11
12
To
tal
Mea
n
SD
P.
sylh
eten
sis
17
5
0
4
7
0
8
0
5
0
4
10
60
5
±5
.08
P.
ten
tori
a
0
12
21
11
0
14
22
12
5
5
3
0
10
5
8.7
5
±7
.81
P.
smit
hii
2
0
4
5
0
0
1
0
8
0
1
2
3
35
2.9
2
±3
.32
G.
ha
mil
ton
ii
24
8
0
0
27
18
12
0
10
3
0
28
13
0
10
.83
±1
0.9
6
H.
thu
rjii
0
0
0
1
0
3
2
1
0
0
0
1
8
0
.67
±0
.98
N.
hu
rum
2
2
0
4
3
0
0
2
0
0
0
0
1
3
1.0
8
±1
.44
N.
nig
rica
ns
0
0
0
2
0
1
0
0
1
0
0
1
5
0.4
2
±0
.67
N.
ga
ng
etic
us
5
0
3
1
4
0
0
3
0
2
0
0
18
1.5
±
1.8
3
C.
ind
ica
0
0
0
0
1
0
0
1
0
0
0
0
2
0
.17
±0
.39
L
ift
net
Sa
mp
lin
g e
ffo
rt
1
2
3
4
5
6
7
8
9
10
11
12
To
tal
Mea
n
SD
P.
sylh
eten
sis
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
P.
ten
tori
a
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
P.
smit
hii
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
G.
ha
mil
ton
ii
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
H.
thu
rjii
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
N.
hu
rum
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
N.
nig
rica
ns
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
N.
ga
ng
etic
us
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
C.
ind
ica
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
13
9
14
0
B
ox t
rap
Sa
mp
lin
g e
ffo
rt
1
2
3
4
5
6
7
8
9
10
11
12
To
tal
Mea
n
SD
P.
sylh
eten
sis
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
P.
ten
tori
a
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
P.
smit
hii
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
G.
ha
mil
ton
ii
0
0
1
2
0
0
1
0
0
0
0
0
4
0.3
3
±0
.65
H.
thu
rjii
0
0
0
0
1
0
0
0
0
0
0
1
2
0
.17
±0
.39
N.
hu
rum
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
N.
nig
rica
ns
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
N.
ga
ng
etic
us
1
0
0
0
1
0
0
0
0
0
0
0
2
0.1
7
±0
.39
C.
ind
ica
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
H
oo
ks
Sa
mp
lin
g e
ffo
rt
1
2
3
4
5
6
7
8
9
10
11
12
To
tal
Mea
n
SD
P.
sylh
eten
sis
0
0
1
0
0
0
0
1
0
0
0
0
2
0.1
7
±0
.39
P.
ten
tori
a
0
2
1
0
2
0
3
1
1
0
0
0
10
0.8
3
±1
.03
P.
smit
hii
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
G.
ha
mil
ton
ii
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
H.
thu
rjii
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
N.
hu
rum
1
0
1
0
0
0
0
0
0
0
0
0
2
0
.17
±0
.39
N.
nig
rica
ns
0
0
0
0
1
0
0
0
0
0
0
1
2
0.1
7
±0
.39
N.
ga
ng
etic
us
1
1
0
0
0
0
0
0
0
0
2
0
4
0.3
3
±0
.65
C.
ind
ica
0
0
0
0
0
0
1
0
0
0
0
0
1
0
.08
±0
.29
C
ast
net
Sa
mp
lin
g e
ffo
rt
1
2
3
4
5
6
7
8
9
10
11
12
To
tal
Mea
n
SD
14
1
Tab
le.
T/T
-2:
Fre
shw
ater
tu
rtle
byca
tch
an
d t
hei
r m
ort
alit
y i
n d
iffe
ren
t fi
shin
g g
ears
G
ill
net
L
ift
net
B
ox
tra
p
Ho
ok
s C
ast
net
B
yca
tch
m
ort
alit
y
Byca
tch
m
ort
alit
y
Byca
tch
m
ort
alit
y
Byca
tch
m
ort
alit
y
Byca
tch
m
ort
alit
y
P.
sylh
eten
sis
60
5
0
0
0
0
2
0
7
0
P.
ten
tori
a
10
5
20
0
0
0
0
10
0
9
0
P.
smit
hii
3
5
12
0
0
0
0
0
0
2
0
G.
ha
mil
ton
ii
13
0
23
0
0
4
1
0
0
5
0
H.
thu
rjii
8
0
0
0
2
0
0
2
0
0
N.
hu
rum
1
3
0
0
0
0
0
2
3
1
0
N.
nig
rica
ns
5
0
0
0
0
0
2
0
0
0
N.
ga
ng
etic
us
18
2
0
0
2
0
4
4
3
0
C.
ind
ica
2
0
0
0
0
0
1
0
0
0
P.
sylh
eten
sis
2
0
0
1
0
0
3
1
0
0
0
0
7
0.5
8
±0
.10
P.
ten
tori
a
2
0
0
0
2
1
1
0
0
3
0
0
9
0.7
5
±1
.06
P.
smit
hii
0
0
0
0
1
0
0
0
0
0
0
1
2
0
.17
±0
.39
G.
ha
mil
ton
ii
0
0
2
0
1
0
1
0
0
0
1
0
5
0.4
2
±0
.67
H.
thu
rjii
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
N.
hu
rum
0
0
0
0
0
0
0
1
0
0
0
0
1
0
.08
±0
.29
N.
nig
rica
ns
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
N.
ga
ng
etic
us
0
0
0
2
0
1
0
0
0
0
0
0
3
0.2
5
±0
.62
C.
ind
ica
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
14
1
142
Plate: P/T-2
A & B: Rescued juvenile turtles caught in fishnets at Bishwanath Ghat
A
B
143
5.2 Grassland Burning:
The study was designed to record the extent of turtle casualties during grassland burning
which is carried out every year during February – April (Plate. P/T- 3.A). Two line
transects were set up in the recently burned grassland patch in each of the study localities;
in Laodubi, Mihimukh, Jamuguri, Dusuti, Goroimari, Arimora, Baghmari, Bordoloni,
Debeswari and Mikirjan) during February-April in 2010 and 2011. Sampling in Laodubi,
Mihimukh, Dusuti, Jamuguri, Arimora and Goroimari were conducted during 2010 and
sampling in rest areas were conducted during 2011. The transects were laid keeping in
mind that- one of the transect is at least 500 m away from any kind of water hole (Site I)
and another was laid in such a way that it is adjacent or ends in a wetland (Site II).
A total of 21individuals (dead= 6 and burnt but alive=15) belonging to five species viz, G.
hamiltonii, M. tricarinata, C. amboinensis, P. tecta and P. sylhetensis (Table. T/T-3) were
recorded during the study. This data was for a total sampling effort of 4, 00,000 m2(=0.4
km2) area for twenty transects covering20,000 m
2(1000mX 20m) within each transect. C.
amboinensis occupied the highest percentage of affected species followed by G. hamiltonii
and M. tricarinata with 34%, 24% and 19% respectively. 76% (n=16) of all the casualty
were in the Site I (i.e. sites far from water) while the Site II accounted for the rest 24%
(n=5) of the casualties (Fig. D/T-7).
The Student’s T- Test value of both the sites (Site I & Site II) in sampling area was
calculated as T= 2.43843104, which is greater than tabulated value (=2.26) at p<0.5 level
and df=9. Thus, the difference in the values of Site I and II is statistically significant,
hence the null hypothesis is rejected.
144
Fig. D/T-7: Comparison of Turtle casualties in Site I and II of all sampling sites
Table. T/T-3: Turtle casualties in grassland burning during 2010-2011
G. hamiltonii C. amboinensis M. tricarinata P. tecta P. sylhetensis Total
Bordoloni site I 0 0 1 0 0 1
Mikirjan site I 1 1 0 0 0 2
Debeswari site I 0 0 1 0 0 1
Laodubi site I 1 1 0 0 0 2
Mihimukh site I 0 1 0 0 0 1
Jamuguri site I 1 1 0 1 0 3
Baghmari site I 0 0 0 0 0 0
Dusuti site I 0 1 1 1 0 3
Arimora site I 0 0 0 0 2 2
Goroimari Site I 1 0 0 0 0 1
Total 4 5 3 2 2 16
Bordoloni site II 0 0 0 0 0 0
Mikirjan site II 0 0 0 0 0 0
Debeswari site II 0 0 0 0 0 0
Laodubi site II 1 0 0 0 0 1
Mihimukh site II 0 0 0 0 0 0
Jamuguri site II 0 1 0 0 0 1
Baghmari site II 0 0 0 1 0 1
Dusuti site II 0 1 1 0 0 2
Arimora site II 0 0 0 0 0 0
Goroimari Site II 0 0 0 0 0 0
Total 1 2 1 1 0 5
0
1
2
3
4
5
6
G. hamiltonii C. amboinensis M. tricarinata P. tecta P. sylhetensis
site I
Site II
species
nu
mb
er
145
Plate: P/T-3
A: Forest staff setting fire in grassland for burning during March
B: Fishing by fringe villagers in wetland inside KNP
A
B
146
5.3 Indirect threats
5.3.1 Inadequate basking due to anthropogenic disturbances:
Tourism related activities mainly the tourist vehicles, picnic, boat safari (Plate. P/T-4)
were recorded as disturbing factors for the basking turtles in Brahmaputra and Diffolu
River. Moreover, illegal fishing in certain wetlands (Plate. P/T -3.B), in Mora Diffolu
River (Plate. P/T-1.B), the agricultural activities including presence of human, livestock
drinking and bathing, pumping of water to the field from Mora Diffolu River has impact
not only on the basking turtles but also on their breeding.
Being inside the park boundary the Jiya Diffolu River and all the wetlands in our study
site were free from fishing activities. While almost the whole stretch of Mora Diffolu
River and some parts in the Brahmaputra River were extensively exploited for fishing. The
Brahmaputra hold 64% and Mora Diffolu had 36% of the fishing activities of the study
sites (Table. T/T-5). Six different types of anthropogenic origin disturbances to the
basking activity have been identified. They were fishing, snail collection, tourist vehicles,
tourist boats, picnic and various agricultural activities including pumping of water to fields
(Table. T/T-4). Mora Diffolu river has the highest disturbances while, the Jiya Diffolu and
wetland habitat had the least (Fig. D/T-8).
The presence of disturbances has negative impact on the assembly of basking turtles (Fig.
D/T-9). It was observed that the Mora Diffolu River at the southern boundary of the park
had the highest anthropogenic origin disturbances in the form of fishing, tourism, picnic,
agricultural activities etc. and had the least number of basking turtle assembly throughout
the whole sampling zones. While another slow flowing river the Jiya Diffolu has the
highest basking turtles (Mean and SD= 277.9 ±4.35) and least disturbances (Fig. D/T-8).
The only disturbance is in the form of tourist vehicle in a sampling zone only. In
Brahmaputra River extensive fishing activities along with tourist boats disturbed the
basking turtles. However, the activities fishing was evident only in the sampling areas at
fringe of the park in Bishwanath Ghat and Dhanbari, but no fishing activities were
observed in other sampling sites. The maximum number of fishing activities were seen in
Bishwanath ghat (mean and SD, 36.766 ±13.38) followed by Laodubi- Kaziranga beat
147
stretch of Mora Diffolu river and Dhanbari of the Brahmaputra River. However, all the
sampling sites of Beels and Jiya Diffolu were devoid of such disturbances.
Jiya Diffolu Mora Diffolu Wetlands Brahmaputra0
10
20
30
40
50
60
70
80
250
300Va
lues
Basking turtles
Fishing
Snail collection
Tourist vehicle
Tourist boat
Agricultural activity
Picnic
Fig. D/T-8: Basking turtles and different disturbances in study areas
Table. T/T-4: Mean basking turtles and disturbances per sampling day
Basking
Turtles
Fishing Snail
collection
Tourist
vehicle
Tourist
boat
Agricultural
activities
Picnic
Jiya Diffolu 277.9
±4.35
0 0 9.57
±2.34
0 0 0
Mora Diffolu 27.78
±3.26
13.79
±2.73
4.1
±2.22
28.75
±1.86
2.2
±1.22
20.23
±2.23
5.21
±1.23
Wetlands 79.87
±5.83
0 0 13.9
±1.56
0 0 0
Brahmaputra 211.63
±2.31
10.12
±2.87
0 0 9 .0
±3.52
8.23
±1.23
4.53
±3.22
148
Table.T/T-5: Mean Number of fishing incidence/ fishing boats
Sampling sites -Jiya Diffolu Mean SD
SSJD 1: Holalpath 0 0
SSJD 2: Kathonibari 0 0
SSJD 3: Turtle point 0 0
SSJD 4: Azagar 0 0
SSJD 5: Pengajan 0 0
Sampling sites-Mora Diffolu
SSMD 1: Laodubi Ghat 10.389 ±3.795
SSMD 2: Mihimukh 3.4278 ±1.489
SSMD 3: 2nd
Elephant Riding Tower 0 0
SSMD 4: Haldibari 3.887 ±1.402
SSMD 5: Bagori 3.500 ±1.384
Sampling sites-Beels :
SSW 1: ArimoraBorbeel 0 0
SSW 2: Baruntika-Bhaisamari Beel 0 0
SSW 3: Mihibeel 0 0
SSW 4: Sohola 0 0
SSW 5: Mona Beel 0 0
Sampling sites- Brahmaputra River
SSB 1: Bishwanath Ghat 36.766 ±13.384
SSB 2: Arimora 0 0
SSB 3: Debeswari 0 0
SSB 4: Maklung 0 0
SSB 5: Dhanbari 1.650 ±1.160
(Abbreviations: SSJD= Study sites in Jiya Diffolu river, SSMD= Study sites in
Mora Diffolu river, SSW= Study sites in Wetlands,
SSB= Study sites in Brahmaputra river)
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Plate: P/T-4
A: Boat safari in Brahmaputra disturbs the basking turtles
B: Fishing activities and a basking P. tentoria in Bishwanath Ghat of Brahmaputra
A
B
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5.3.2 Turtle market
Fishing is extensively practiced by the local inhabitants, in the Mora Diffolu and the
Brahmaputra River (Plate. P/T-1) as well as a majority of fringe villagers harvest fish from
wetlands (Plate. P/T-3.B) inside the Kaziranga NP boundary, where turtles are often
caught accidentally in fishnets. This present study recorded nine freshwater turtle species
that were accidentally caught in the fishnets in Bishwanath Ghat of the Brahmaputra
River. They were- Nilssonia hurum, N. gangeticus, Chitra indica, Pangshura sylhetensis,
P. tentoria, P. smithii, Geoclemys hamiltonii, Hardella thurjii and N. nigricans. The
turtles caught from the Brahmaputra and Mora Diffolu river of Kaziranga NP are sold in
the nearby markets especially in Bishwanath Ghat and Bokakhat. The juveniles and small
sized turtles were bought by religious Hindu devotees for releasing in the temple tanks like
the Nagshankar Temple, which is only 15 km away.
5.3.3Basking log removal and habitat degradation:
Removal of basking logs from Brahmaputra and Mora Diffolu River especially in the
boundary of the park happens to be another important category of threat to the chelonians
of Kaziranga NP. Removal of log is generally associated with the fishing activities.
Consequently, the intense fishing zones were observed with little or no dead woods
available for basking (Fig. D/R-17).
Moreover, the practice firewood collection for domestic as well as commercial use can be
observed in the semi evergreen woodland patches at Karbi-anglong foothill. Boulder
mining activities, stone quarries present in the Karbi-anglong district foothills and jhoom
cultivation has degraded the semi evergreen forest habitat. The loss of such habitat is
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likely to impact the existence of endangered chelonian species Manouria emys and Cuora
mouhotii along with Cyclemys gemeli.
5.3.4 Bankline erosion and siltation of wetlands:
The official area under mainland Kaziranga was 428.7 km2in 1973 when it was declared
National Park (Lahan and Sonowal, 1973), but in the recent years the area has been
reduced considerably due to erosion by the Brahmaputra River during flood in the South
boundary. Since, 1973 to 2010 a total of 48.05 km2 area has been eroded by the
Brahmaputra River.
The erosion is mainly in the north western and north eastern part. Such erosion has
reduced the grassland area of the park considerably and as a consequence the truly
grassland dweller species such as Melanochelys tricarinata is likely to be affected.
The area under wetland over a period of 30 years from 1967-68 to 1997, also have reduced
from 8.5% of total area to 6.7% as a result of considerable erosion, siltation and
fragmentation of beels (Kushwaha et al., 2000). The decrease in the area and depth of
wetlands will directly affect the wetland turtle species including the critically endangered
Nilssonia nigricans and endangered Chitra indica and high water depth preferring species
like Hardella thurjii.