This is a thesis defense presentation submitted to the Department of Environmental Science of Savitribai Phule Pune University (SPPU) in the month of June 2021 for the partial fulfillment of the requirements for the award of the degree of Environmental Science.

1. Assessment of the status of the endangered Gangetic River Dolphin
of the Brahmaputra River and the socio-ecological attitude of
piscatorial communities towards the species in the riverine areas of
Silghat and Mayong in Assam
A thesis defense presentation by
Shibanjali Mahanta,
bearing Student ID No. N19401017,
under the guidance of
Dr. Ashalata Devi (Associate
Professor, Tezpur University)
from the Department of
Environmental Science, SPPU
P h o t o C r e d i t s : G a n e s h C h o w d h u r y
S o u r c e : w w w . n a t u r e i n f o c u s . i n
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Abstract
The thesis investigates the status of the Endangered (EN)
Gangetic River Dolphin in the understudied area of the
Brahmaputra River in Assam which is home to
approximately 13.2% of the entire Ganges River Dolphin
population in the world. The study tests two research
hypotheses to ascertain (a) the exact time/ range of time of
the species’ migration from the main river stream to its
upstream tributaries to direct strict implementation
measures of conservation legislation during that period, and
(b) the spatial and prey-resource overlap between fishing
activities and the Gangetic river dolphin surfacing and
foraging areas and test the so-formed research hypothesis
by checking for a linear association between the extent of
fishing activities in the river segments surveyed and
Gangetic river dolphin abundance estimates. The thesis also
tries to understand the effects of fishing activities and the
socio-ecological attitude of the piscatorial communities
towards the imperilled species in the two study sites
chosen for the project.
The topic was chosen to address a few missing links in
literature and in the process set the stage for more
scientifically motivated research on this sensitive and
relevant subject, particularly in the state of Assam.
F i g u r e 1 : S i t e I - S i l g h a t To w n , A s s a m a t
s u n s e t

3. Introduction
P A R T 0 1
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4. 04
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Research Problem
• The decreasing population trend of the
species in the Brahmaputra River system;
• The lack of credible time series of
abundance estimates for most of the
species' range;
• The lack of rigorous quantitative data
(current or historical) on numbers,
mortality, extent of occurrence, and area of
occupancy of the species;
• The absence of strong legislation and a
PAN for the species in Assam.
W H A T I W A N T T O A D D R E S S
Research Aim
To understand the Ganges River Dolphin status,
locally known as ‘xihu’ in Assam, its habitat use
and habitat selection in two segments of the
Brahmaputra River System with significantly
contrasting dolphin abundance estimates.
The research aims to compare the two sites in a
holistic pattern to provide a quantitative analysis
of relationships between habitat use and
hypothesized ecological and social co-variates
and responses to existing fishing and other
anthropogenic pressures faced by the species.
W H A T I W A N T T O A C H I E V E

5. Research
Objectives
H O W I W A N T T O A C H I E V E T H E
R E S E A R C H A I M
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• Assess the status of the Gangetic River Dolphin
population estimates during the minimum river-
discharge season in two remote river segments
of the Brahmaputra River near Silghat Town and
Mayong Village;
• Understand the spatial and prey-resource overlap
between fishing activities and the Gangetic river
dolphin surfacing and foraging areas;
• Understand the effects of fishing activities and
the socio-ecological role and attitude of the
piscatorial communities towards the imperiled
species in the two study sites.

6. Hypothesis Statements
• ρ ≠ 0: There is a temporal decrease in the
population estimates of the Gangetic River
Dolphins of the surveyed river segments during the
minimum river discharge season from February to
March 2021;
• ρ ≠ 0: There is a linear association between the no.
of fishing boats and Gangetic River Dolphin
population estimates in the river segments.
Limitations of the Study
• Lack of prior exploratory studies on the topic;
• Measure used to collect the data;
• Sample size;
• Access to resources;
• Longitudinal Effects and COVID-19
Figure 2: Site I (Silghat Town, February)
Figure 3: Site II (Mayong Village, March)
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7. Review of
Related Literature
P A R T 0 2
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8. Scottish anatomist, zoologist,
and ex-curator of the Indian
Museum in Calcutta- John
Anderson was the first to
account for the distribution
range, morphology, and
anatomy of the Platanista
species in 1879.
F I R S T
H I G H L I G H T
Surveys conducted by various
researchers in the accessible
river segments of Asia that act
as Gangetic river dolphin
habitats from 1982-2019, list
population estimates ranging
from 45 (Singh 1985) in some
river tributaries to 1500+ in
some other main river stems
(Smith, 1993; Behera, 1995;
Sinha 1999; Sinha et al., 2010a).
S E C O N D
H I G H L I G H T
In comparison to the Ganges
River system, little research on
dolphins has been undertaken
in the Brahmaputra River
system of Assam in India
(Wakid & Braulik, 2009).
T H I R D
H I G H L I G H T
As with most of its distribution
range, the GRD inhabits a
human-dominated
environment amplifying the
possibilities of man-animal
conflicts by a huge percentage
thus appropriate
implementation of science-
backed legislation is important
to secure a peaceful co-
existence (Kelkar et al., 2010)
.
F O U R T H
H I G H L I G H T
Related Literature
01 02 03 04
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9. Research Methods
P A R T 0 3
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Study Area
F I G U R E 4 : M A P O F A S S A M W I T H T H E B R A H M A P U T R A
R I V E R A L O N G W I T H T H E T W O S T U D Y S I T E S

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Study Area
F I G U R E 5 : S I T E I - S I L G H AT T O W N , N A G A O N , A S S A M

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Study Area
F I G U R E 6 : S I T E I I - M A Y O N G V I L L A G E , M O R I G A O N , A S S A M

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Project Timeline
Literature Review, and
Familiarization with
different research
techniques that can be
employed for the purpose
of the thesis.
On-field Data Collection Analysis and Discussion of
Results
Finalization of Dissertation
and Thesis Write-up
P H A S E 0 1
( D E C - J A N )
P H A S E 0 2
( F E B - M A R )
P H A S E 0 3
( M A R - A P R )
P H A S E 0 4
( A P R )

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Research Approach
D E S C R I P T I V E & A N A L Y T I C A L Q U A N T I T A T I V E R E S E A R C H
I N F L U E N C E D B Y A S U B - P O S T P O S I T I V I S T W O R L D V I E W
R E A S O N 0 1 R E A S O N 0 2 R E A S O N 0 3
The first objective includes the
assessment of the population
status of the species in the two
study areas- which involves
comparing numbers between
the two sites hence, a
population estimates' count
method was chosen to test the
research hypothesis.
The second objective was to
understand the spatial and
prey-resource overlap between
fishing activities and river
dolphin surfacing and foraging
areas and hence, definite
numbers were required to test
the research hypothesis.
The third objective was to
understand the socio-
ecological attitude of the
piscatorial communities at both
study sites and hence,
quantifiable data was required
to make meaningful
interpretations.

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Data Collection Methods
M E T H O D 0 1 M E T H O D 0 2
MODIFIED VESSEL-BASED
DIRECT COUNT METHOD
(SMITH & REEVES, 2000)
STRUCTURED SCHEDULES
FOR THE SOCIO-
ECOLOGICAL STUDY
S U R V E Y
D U R A T I O N
• February and March
• 2 times a day
(Morning and
afternoon)
• Three days a week in
each month
S U R V E Y
D U R A T I O N
March and April
S A M P L I N G
M E T H O D
Non-Judgemental
Sampling

16. Results
P A R T 0 4
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Data Analysis Methods
Q U A N T I T A T I V E A N A L Y S I S
O B J E C T I V E 0 1 O B J E C T I V E 0 2 O B J E C T I V E 0 3
• Descriptive Analysis
of Numerical Data
using Tables and
Graphs;
• Inferential Analysis of
Numerical Data using
Student's Paired t-
Test.
Inferential Analysis of
Numerical Data using
Pearson's Correlation Co-
efficient Test and Scatter
Plots.
Descriptive Analysis of
Numerical Data using
research tools such as
frequency distribution
tables, socio-
demographic statistics,
etc.

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Quantitative Results
Research Findings & Highlights
Figure 7: Gangetic river dolphin population estimates vs.
their frequency of occurrence for Site I in February
Figure 8: Gangetic river dolphin population estimates vs.
their frequency of occurrence for Site I in March
Objective 01- Site I

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Quantitative Results
Research Findings & Highlights
Figure 9: Gangetic river dolphin population estimates
vs. their frequency of occurrence for Site II in
February
Figure 10: Gangetic river dolphin population estimates
vs. their frequency of occurrence for Site II in March
Objective 01- Site II

20. • There is a temporal decrease in the population
estimates of the Gangetic river dolphins of the
Silghat and Mayong river segments in the
minimum water discharge season from February
to March 2021;
• In both the sites, the means of population
estimates for the Gangetic river dolphins were
higher for the month of February compared to the
month of March;
• In both sites, the highest number of dolphins were
observed on upstream surveys compared to the
speed of the boats during the downstream
surveys when the vessels plied in the direction of
the river current;
• The average population estimate of the Gangetic
river dolphin was lesser in Mayong village of
Assam where a mean of 15.5 river dolphins (±5.79)
was observed for the month of February and a
mean of 10.7 river dolphins (±6.25) was observed
for the month of March compared to the mean
estimate of 22.5 (±6.69) for the month of
February, and 14.2 river dolphins (SD ±4.7) for the
month of March in Silghat.
H I G H L I G H T 0 1
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Quantitative
Results
R E S E A R C H F I N D I N G S
A N D H I G H L I G H T S
Table 1: Paired t-test results of SITE I for February and March

21. Quantitative Results
Research Findings & Highlights
Figure 11: Scatter plot showing a fairly linear association between
fishing boats and Gangetic river dolphin abundance estimates in
SITE I
Objective 02- Site I
SITE I: r value +0.6
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Quantitative Results
Research Findings & Highlights
Figure 12: Scatter plot showing a fairly linear association between
fishing boats and Gangetic river dolphin abundance estimates in
SITE II
Objective 02- Site II
SITE II: r value +0.7

23. • In both sites, there was a linear association
between the no. of fishing boats and
Gangetic river dolphin abundance estimates
in the river segments indicating an overlap in
the Gangetic river dolphin foraging areas and
the fishing areas preferred by the local
fishers;
• A stronger correlation (r= +0.7) in the two
variables, i.e. no. of fishing boats and
Gangetic river dolphin abundance estimates
in the river segments was observed in Study
site II, i.e. Mayong village of Assam compared
to Study Site I (r= +0.6), i.e. Silghat Town.
H I G H L I G H T 0 2
02
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Quantitative
Results
R E S E A R C H F I N D I N G S
A N D H I G H L I G H T S
Figure 13: Fishers leaving for their daily catch in the
morning at Silghat Town, Assam

24. • Most of the inland fishers (88% in Silghat
town and 52% in Mayong village) fish during
the early morning and afternoon hours,
which coincides with the diurnal activities of
the species;
• In both Sites, I and II, a very close association
was observed between the agreement/
disagreement levels of various respondents
on legislations such as the Assam Fisheries
Rules, 1953, etc. and their opinions on the
role(s) played by fishers in the conservation
of the diverse biodiversity in the study area;
• In both Sites I and II, a significant association
was observed between educational levels
and awareness about the imperiled status of
the Gangetic river dolphins in the state.
• The study also found the unrevealed use of
destructive fishing techniques to increase
the already depleted fish abundance in the
Brahmaputra River.
H I G H L I G H T 0 3
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Quantitative
Results
R E S E A R C H F I N D I N G S
A N D H I G H L I G H T S
Figure 14: Fishers’ schedule-based socio-ecological survey

25. Conclusion
P A R T 0 5
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26. Study highlights
Interpretation
of findings
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U N C O V E R E D K E Y R E S E A R C H T R E N D S
• The seasonal migration of the GRDs from the
main river stream to its tributaries occurs
between the months of February and March
2021 which coincides with the pre-monsoon
season in the north-east;
• Study Site II, compared to Study Site I had a
relatively higher influence of anthropogenic
fishing activities on the area's extant GRD
population; and
• There was a significant lack of awareness among
the piscatorial communities regarding the
importance of conserving the GRD species-
more so in Site II, compared to Site I.
A G R E E M E N T S & D I S A G R E E M E N T S
W I T H H Y P O T H E S I S
Both the alternate research hypotheses were
accepted.

27. N O T E S F O R F U T U R E R E S E A R C H
• Need for the development of a robust and easy to
implement technique for freshwater cetacean
density and abundance studies;
• Exploratory research on the ecological behaviour of
Gangetic river dolphins;
• Development of co-management initiatives by the
concerned regulatory bodies;
• Development of a Gangetic river dolphin sanctuary
in the highest river dolphin abundant site in Assam
and delineation and declaration of all the major
dolphin hotspots and breeding grounds in Assam
as IUCN Marine Protected Areas, etc.
Implications of
the research
Areas of improvement
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P R A C T I C A L A P P L I C A T I O N S
• The study confirmed the findings of a study conducted by Braulik
& Wakid, (2009) in Assam for the IUCN;
• The study also found the beginning of seasonal migration of the
Gangetic river dolphins from the main Brahmaputra channel to its
tributaries to start sometime between mid February and early
March;
• It was clear from the findings of the study that in both sites, there
was a strong overlap between the areas used by the Gangetic river
dolphins to travel, forage, and rest with the areas used by the
fishers to catch fish resources to sustain their living;
• Very few individuals were aware of the vulnerable state of the
species in Assam as well as India

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A Final Thank You
F i g u r e 1 5 : S i t e I - B a n k s o f t h e B r a h m a p u t r a R i v e r
d u r i n g s u n s e t a t S i l g h a t T o w n , A s s a m