DISTRIBUTION PATTERNS, HABITAT CHARACTERISTICS AND POPULATION ESTIMATES OF

IRRAWADDY DOLPHINS (OrcaeUa brevirostris) IN KUCHING BAY, SARAWAK

Cindy Peter

Master of Science 2012

Pusat Khidmat Maklumat Aluld ,I I •

UNIVERsm MALAYSIA SARAW I

DISTIBUTION PATTERNS, HABITAT CHARACTERISTICS AND POPULATION

ESTIMATES OF IRRAWADDY DOLPHINS (Orcaella brevirostris) IN KUCHING BAY,

SARAWAK

Ii I'

CINDY PETER

A thesis submitted in fulfillment of the requirements for the degree of

Master of Science

Institute Biodiversity and Environmental Conservation UNIVERSITI MALAYSIA SARA W AK

~ I 2012

I

Declaration

I hereby declare that no portion of the work referred to in this thesis has been submitted in support of an application for another degree or qualification to this or any other university or institute of higher learning.

(Cindy Peter) September 2012

11

Acknowledgements

First of all, many thanks I offer to the Lord, my God for all the blessings which He has showered

unto me. When times seem pitch black, He always provides a way out. For all the love, and for

putting up with my not-so-traditional choice of work by my parents, Peter Alek anak Radin and

Jusa Chee, no amount of love or gratitude can ever repay your patience. Not forgetting my

brothers, Herman Peter and Allan Peter for their financial and moral support; this thesis and this

MSc is as much as yours as it is mine. I hope I made all of you proud.

Prof Dr Andrew Alek Tuen, who was my undergraduate lecturer and then my supervisor, thank

you for giving me the opportunity to work as a Research Assistant on the Sarawak Dolphin

Project when I came knocking on your office door four years ago. Your calmness and faith have

taught me how to face the world with a cafm assurance. Dr Gianna Minton, (yes I have to call

you Dr in here) how can I ever thank you. I have had the privilege to call you my co-supervisor,

mentor, teacher, colleague, and most importantly a friend. For all that you have taught me, from

the marine mammal science perspective and also through your stories, experiences and advice, I

really cannot thank you enough. The only regret I have is finishing this thesis while you are busy

packing for your move. You, Keith and the girls have made me feel so welcomed, I really cannot

thank you enough. To the administrative staff of Institute of Biodiversity and Environmental

Conservation (IBEC) circa 2008 - 2012, many thanks and gratitude are owed to all of you for

offering help during fieldwork, with all the paperwork and sometimes by just being there for a

quick chat.

I would like to express my sincere gratitude to Sarawak Shell Berhad who funded the Sarawak

Dolphin Project for the first year of this study and also the community outreach programme

through the Shell Chair Endowment throughout 2010 - 2011. I am extremely grateful also to

III

Universiti Malaysia Sarawak (UNIMAS) for its support in providing me a two-year Zamalah

Postgraduate scholarship from 2009 - 2011. Generous grants were also rewarded by the Ocean

Park Conservation Foundation Hong Kong (OPCFHK) and Ministry of Science, Technology and

Innovation (MOSTI), Malaysia which sustained my allowance and fieldwork throughout the

duration of this study.

Special thanks are accorded to Mr Rahim Bugo, the Manager of the Permai Rainforest Resort for

providing the resort's boat, boatmen (Bol, Wan Amin, Taufik, Rosmadi) instructors (John,

Rudy) and various other logistic support. The aid given by the resort has extremely lightened the

burden of running costs for this project. Many thanks also to Mr Oscar Choo, CPH Travel for

providing research vessel and boatmen (Jamadi, Roslan) during the commencement of this

project.

A major part of analyses in this thesis would not have been possible without the help of Prof Dr

Wang Yin Chai and Lee Guan Heng from the GIS lab in FIT UNIMAS who spent many hours

guiding me in the use of ArcGIS. To Mike Meredith, Gill Braulik, Robert Brownell Jr, Phil

Hammond, Lindsay Porter and Louisa Ponnampalam, who provided methodology and statistical

advice as well as visited our tiny project here in Borneo, thank you.

I would also like to thank the Sarawak Forestry Corporation for the valuable contribution of staff

and logistical support during the 2008-2009 surveys, and the Sarawak Forestry Department for

the relevant permits to conduct dolphin surveys in Kuching Bay.

Anna Norliza and Jenny Ngeian, Research Assistants to the Sarawak Dolphin Project and fellow

friends, thank you for all your assistance during fieldwork and putting up with my mood swings.

iv

It's just us now so let's make ze boss proud! Much gratitude to Pang Sing Tyan, William

Beavitt, Pui Yong Min, Nurul Ashikeen Abdul Razak, Ada Bong and all previous and present

postgraduates of IBEC for your time assisting me in the field when I needed an extra hand and a

pair ofeyes and moral support throughout the duration of my studies. Research/student life was a

lot more colourful with all of you around.

Especially to my friends, Arlyne Davina, leniffer Liah, Tina Koh and Tiffany Nakita thank you

for always being there when I needed a lift, for all the laughter and tears, secrets and heartaches,

smiles and frowns. They say friends are the families that you choose and I would not want any

other sets of family friends. Thank you for making my life colourful.

Many friendships and acquaintances were formed throughout the years I have worked on this

research and thesis, it is impossible to list each and everyone of you. Know that I hold you dear

in my heart and thank you for keeping me in your thoughts and prayers. Thank you.

v

Distribution patterns, habitat characteristics and population estimates of Irrawaddy

Dolphins (Orcaella brevirostris) in Kuching Bay, Sarawak

Abstract

( rrrawaddy dolphins (Orcaella brevirostris) are known to be rIverme and coastal dwelling

animals which place them under pressure from human activities like fishing, coastal

developments and environmental pollution. Previously, there was a lack of baseline information

on the population of Irrawaddy dolphins that are present in Kuching Bay. This lack of data

impeded conservation and management efforts, as no one could determine how many dolphins

there are, how they are distributed on a fine scale, or what their preferred habitat characteristics

ar~

In order to overcome this, small boat surveys were conducted in the Kuching Bay from June

2008-September 2010. The first objective of the study aimed to map the distribution patterns and

determine the relative abundance of Irrawaddy dolphins in the waters of Kuching Bay. Surveys

covered a total of 4,091 km and 317 hours. Irrawaddy dolphins were sighted 41 times on-effort

representing an estimated total of 183 individuals. The mean encounter rate throughout the 44

days of survey was 0.30 sightings per hour. Analysis of encounter rates within 2km by 2km grid

cells showed high densities of Irrawaddy do'lphins in the Salak estuary, Bako peninsula and

offshore ofTelaga Air.

The second objective was to define the habitat preferences of Irrawaddy dolphins by conducting

water parameter samplings and measuring the physical characteristics of the sighting sites.

Kruskal-Wallis U tests showed that the animals' distributions are not significantly related to

vi

water temperature, pH, depth or distance to land. However the dolphin distribution was

statistically significant for the different categories of salinity (p < 0.05) and distance to

rivermouth (p < 0.05). Fisher's exact test indicated that Irrawaddy dolphins are statistically more

likely to be present in waters within a 6 km radius from rivermouths. Dolphins' distributions are

also affected by tide levels as Mann-Whitney U tests proved a statistically significant difference

(p < 0.05) in dolphin distribution between tide levels lower than 2.0 m and tide levels higher than

2.0 m.

The third objective of the study was to obtain absolute abundance estimates of Irrawaddy

dolphins in Kuching Bay. This was achieved by using mark-recapture techniques on photo­

identified individuals to generate population estimates for the Kuching study area. Based on this,

the best estimate of the Irrawaddy dolphin population in Kuching Bay is 233 dolphins (CV =

22.5%,95% CI 151-360).

The fourth objective was to learn about the individual movement patterns of the Irrawaddy

dolphins in Kuching Bay by identifying individual dolphins through photo-identification and

plotting the observed locations of identified individuals. Seventeen individuals were

photographed more than once and four individuals were photographed in both the Salak­

Santubong and Bako-Buntal bays on a few occasions. The furthest distance an individual

dolphin traveled between sighting locations in the study was approximately 40 km. In addition,

resighted individuals were photographed across different survey months as well as different

survey years.

This study showed that the Irrawaddy dolphins of Kuching Bay prefer areas of lower salinity,

closer to land and rivermouths, with tidal state also playing a significant role in ~heir distribution.

vii

The estimate obtained in this study showed that the population in Kuching Bay is relatively

small and the movement patterns analysis proved that several individual dolphins utilize both the

Salak-Santubong Bay and Bako-Buntal Bay. Therefore, any management or conservation efforts

for the Irrawaddy dolphins will need to be applied to both bays.

Keywords: Irrawaddy dolphin, Kuching Bay, distribution, habitat preference, population

estimates.

VIII

Taburan, ciri-ciri habitat dan anggaran populasi lumba-Iumba Irrawaddy (Orcaella

brevirostris) di Teluk Kuching, Sarawak

Abstrak

Lumba-lumba Irrawaddy (Orcaella brevirostris) adalah haiwan yang hidup di kawasan sungai

dan pesisiran pantai. Oleh yang demikian, haiwan ini terdedah kepada tekanan daripada

kegiatan manusia seperti memaneing, pembangunan pesisiran pantai dan peneemaran alam

sekitar. Sebelum ini, terdapat kekurangan maklumat asas mengenai populasi lumba-lum'ba

Irrawaddy di Teluk Kuehing. Kekurangan maklumat ini menghalang usaha pemuliharaan dan

pengurusan kerana tiada pihak yang dapat menentukan jumlah bilangan lumba-lumba ini,

taburan terperinei atau habitat pilihan haiwan terse but.

Untuk mengatasi kekurangan ini, kajiselidik menggunakan bot keeil telah dijalankan di Teluk

Kuehing dari Jun 2008 - September 2010. Objektif pertama kajian ini adalah untuk memetakan

pola taburan dan menentukan kelimpahan relatif lumba-lumba Irrawaddy di Teluk Kuehing.

Survei ini meliputi 4, 901 km dan 317 jam. Lumba-lumba Irrawaddy telah dijumpai sebanyak 41

kali semasa tempoh pemerhatian (on-effort) dengan anggaran terbaik sebanyak 183 individu.

Min kadar pertemuan dalam kajian selama 44 hari itu adalah 0.30 pemerhatian sejam. Analisa

kadar pertemuan dalam sel grid 2 km x 2 km menunjukkan kepadatan lumba-lumba Irrawaddy

yang tinggi di muara Sungai Salak, semenanjung Bako dan luar pesisiran pantai Telaga Air.

Objektif kedua adalah untuk menakrifkan habitat pilihan lumba-lumba Irrawaddy dengan

merljalankan pensampelan parameter air dan mengukur ciri-ciri jizikal di lokasi pemerhatian

haiwan tersebut. Ujian Kruskal-Wallis menunjukkan tiada perbezaan signifikan antara pola

taburan lumba-lumba dengan suhu air, pH, kedalaman mahupun jarak ke darat. Walau

IX

bagaimanapun, pola taburan lumba-lumba adalah berbeza dengan kategori berlainan untuk

kemasinan (p < 0.05) dan jarak ke muara sungai (p < 0.05). Ujian ketepatan Fisher

membuktikan secara statistik bahawa lumba-lumba Irrawaddy lebih cendurung untuk berada

dalam jarak 6 km dari muara sungai. Pola taburan lumba-lumba juga dipengaruhi oleh aras

pasang surut kerana ujian Mann-Whitney U membuktikan perbezaan (p < 0.05) pola taburan

lumba-lumba antara aras kurang dari 2.0 m dan melebihi 2.0 m.

Objektij ketiga kajian adalah untuk mendapatkan anggaran kelimpahan mutlak lumba-lumba

Irrawaddy di Teluk Kuching. Ini telah dicapai melalui teknik tanda-tangkap semula pada

individu yang dikenalpasti melalui pengecaman gambar untuk mendapatkan anggaran populasi

un/uk kawasan kajian di Kuching. Dengan ini, anggaran terbaik untuk lumba-lumba Irrawaddy

di TelukKuching adalah sekitar 233 ekor (CV = 22.5%, 95% CI 151 - 360).

Objektij keempat adalah untuk mempelajari pola pergerakan lumba-lumba Irrawaddy dengan

mengenalpasti individu lumba-lumba melalui pengecaman gambar dan memplotkan lokasi

individu yang telah dikenalpasti. Tujuh belas ekor dolphin telah diambil gambar lebih dari

se!cali dan empat ekor telah diambil gambar beberapa kali di kedua-dua Teluk Salak-Santubong

dan Teluk Bako-Buntal. Jarak paling jauh yang dilalui oleh seekor lumba-lumba antara

kawasan pemerhatian adalah kira-kira 40 km. Selain itu, lumba-lumba turut digambar dalam

bulan !cajian yang berlainan dan juga antara tahun kajian yang berlainan.

Kajian ini menunjukkan bahawa lumba-lumba Irrawaddy di Teluk Kuching mengutamakan

kawasan bersaliniti rendah, lebih dekat dengan darat dan muara sungai. Aras pasang surut

JuruJ memainkan peranan penting dalam menentukan pola taburan lumba-lumba. Anggaran

individu yang diperolehi dalam kajian ini menunjukkan bahawa populasi lumba.-lumba di Teluk

x

Kuching adalah agak keci!. Di sam ping itu, analisis pola pergerakan juga membuktikan bahawa

beberapa individu lumba-lumba menggunakan kedua-dua Teluk Salak-Santubong dan Teluk

Bako-Bunta!' Oleh itu, usaha pemuliharaan atau pengurusan untuk lumba-lumba Irrawaddy

perlu mengambil kira kedua-dua teluk terse but.

Kala kunci: Lumba-lumba Irrawaddy, Teluk Kuching, taburan, habitat pilihan, anggaran

populasi.

xi

Pusat Kbidmat Maldumat Akademik UNlVEKSm MALAYSIA SARAWAK

Table of contents

No. Contents Page No.

Declaration ii

Acknowledgements iii

Abstract VI

Abstrak IX

Table of contents xii

List of figu res xv

List of tables XVI

1.0 Chapter 1: Introduction

1. 1. General introduction

1.2 Rationale of study and hypothesis 3

1.3 Research objectives 4

1.4 Thesis outline 5

2.0 Literature review

2.1 Distribution of Irrawaddy dolphins in the region 6

2.2 Habitat preferences of Irrawaddy dolphins in the region 8

2.3 Population estimates of Irrawaddy dolphins 10

2.4 Individual ranges of Irrawaddy dofphins in Asia 14

2.5 Threats faced by Irrawaddy dolphins and other cetaceans in the 14 Kuching Bay

2.6 Evaluation of research methods applicable to this study 19

2.6.1 Methods to evaluate distribution and habitat preferences 19

2.6.2 Methods for determination of population estimates for marine 23 mammals

2.6.3 Methods for assessment of individual range and movement patterns 25

XII

2.7 Significance of study 27

3.0 Chapter 3: Distribution and habitat preferences of Irrawaddy dolphins (Orcaella brevirostris) in the nearshore and estuarine waters of Kuching Bay, Sarawak.

3.1 Introduction 28

3.2 Methods and materials 29

3.2.1 Study location 29

3.2.2 Field methods 31

3.2.3 Data processing 34

3.3 Results 38

3.3.1 Encounter rates and relative abundance 38

3.3.2 Habitat preferences 49

3.4 Discussion 49

3.4.1 Distribution patterns of the species 49

3.4.2 Habitat characteristics of Irrawaddy dolphins 51

3.5 Conclusions 52

4.0 Chapter 4: Movement patterns and population estimates of Irrawaddy dolphins in Kuching Bay using photo-identification.

4.1 Introduction 54

4.2 Methods and materials 55

4.2.1 Boat surveys and study area 55

4.2.2 Data collection 56

4.2.2.1 Photograph collection 56

4.2.2.2 Photograph storage and classification 58

4.2.2.3 Photograph analysis 60

xiii

4.3 Results 64

4.3.1 Matching of photographs 64

4.3.2 Movement patterns of Irrawaddy dolphins in Kuching Bay 65

4.3 .3 Population abundance estimation ofIrrawaddy dolphins in Kuching 66 Bay

4.4 Discussion 73

4.4.1 Challenges of working with the species 73

4.4.2 Resights and individual movement 74

4.4.3 Population abundance estimates 75

4.5 Conclusions 79

5.0 Chapter 5.0: General discussion, recommendations and conclusions

5.1 General discussion 81

5.2 Recommendations 83

5.3 General conclusions 85

References 86

Appendix A 101

Appendix B 102

xiv

List of Figures

No. Title Page no. 3.1 Location of Kuching Bay designated by a box. 1. Santubong River; 2.

Salak River; 3. Sibu Laut River; 4. Buntal River; 5. Talang-Satang National Park; 6. Bako National Park; 7. Mount Santubong; 8. Muara Tebas. 9. Kuala Rambungan.

Boat survey tracks (on effort portions only) covered between 15 July 2008 and 26 May 2010. Line-transects ran approximately 45 degrees parallel to the coast with areas encompassing the study location.

3.2

3.3 Boat survey tracks (on effort portions only) and location of cetacean sightings between 15 July 2008 and 26 May 2010.

3.4 Encounter rates per hour oflrrawaddy dolphins according to seasonality.

3.5 Irrawaddy dolphin relative densities represented by the number of sightings per km searched in 2km by 2km grid cells.

3.6a - f Percentage of dolphin presence in relation to different depth, distance to rivermouth, distance to land, salinity, temperature and pH categories.

3.7 On-effort sightings of Irrawaddy dolphins at tidal heights of lower than 2m vs. higher than 2m.

4.1 Locations in Kuching Bay where photo-identification efforts were concentrated. I. Santubong River; 2. Salak River; 3. Sibu Laut River; 4. Buntal River; 5. Talang-Satang National Park; 6. Bako National Park; 7. Mount Santubong; 8. Muara Tebas. 9. Kuala Rambungan.

4.2 Screenshot of Irrawaddy dolphin photo-identification database with left dorsal fin (LDF) and right dorsal fin (RDF) photos side by side.

4.3a - d Resights of Irrawaddy dolphins based on LDFs and RDFs.

4.4 Discovery curve showing the cumulative number of individuals represented by photo quality 2 and above, with distinctiveness 3 and above.

30

32

39

42

43

46-47

49

57

59

67 -68

69

xv

List of Tables

No. Title Page no. 1.0 Population estimates of Irrawaddy dolphins in Asia using mark- 13

recapture of photo-identified individuals method and other methods.

3.1 Behavioural states and definition (adapted from Lusseeau, 2006 34 and Parra, 2006).

3.2 Species encountered with number of sightings and number of 40 individuals.

3.3 Date of boat surveys with distance and hours spent (total number 41 ofdays spent on survey = 44 days).

3.4 Fisher's exact test results for the different parameters. 45

4.1 Survey months, effort distance and effort hours spent on dolphin 56 watch tours and boat surveys in Kuching Bay.

4.2 Matched photographs of Irrawaddy dolphins in a custom-based 64 Microsoft Access database as of 30 November 2010.

4.3 Distinctiveness scores of left and right dorsal fins for individuals 70 -71 represented by photo quality 2 or higher and proportion of "marked" individuals.

4.4 Estimate abundance of Irrawaddy dolphins in Kuching Bay 72 using program MARK..

xvi

Chapter 1

Introduction

1.1 General introduction

Marine mammals, be it whales or dolphins are often recognized as being keystone species.

These charismatic mega-fauna are valuable as indicators of the health of the environment, due

to their top position in the ocean's food chain. Even so, these marine creatures are poorly

studied in Sarawak, Malaysia. There are over 80 species of whales, dolphins and porpoises in

the world and some 27 of them are documented in Malaysia (Ponnampalam, 2012). Of these

documented species, the most frequently recorded in nearshore habitats of Sarawak is the

Irrawaddy dolphin (Orcaella brevirostris). Irrawaddy dolphins are odontocetes classified under

the family Delphinidae.

Irrawaddy dolphins are closely associated with shallow estuarine and riverine waters in the

Indo-Pacific, from northeastern India east to the Phillipines and this species is unlikely to

colonize offshore islands beyond few ki lometers from the mainland (Dolar et aI., 2002; Smith,

2008). As a species, Irrawaddy dolphins are listed as Vulnerable in the IUCN Redlist of

Endangered Species with five subpopulations in the Ayeyarwaddy River in Laos PDR, the

Mahakam River in Indonesia, the Malampaya Sound in the Phillipines, the Mekong River in

Myanmar and the Songkhla River in Thailand designated as Critically Endangered (IUCN,

2008).

Prior to this study, there was very limited information on marine mammals in Sarawak waters.

Historical field observations noted their presence in waters off Peninsular Malaysia (Gibson­

Hill, 1949; Lewin, 1958; Ratnam 1982). Occasional sightings, strandings and deaths of

cetaceans have also been reported (e.g. Beasley and Jefferson, 1997; Dolar et ai., 1997;

Nadarajah, 2000; Jaaman, 2004) but the status of marine mammal populations in Malaysia is

still not fully understood. Following the turn of the century, research efforts on marine

mammals in Cowie Bay, Sabah slowly increased due to the involvement of Universiti

Malaysia Sabah (Jaaman, 2004; Jaaman, 2006) but dedicated surveys were still lacking in

Sarawak. The Sarawak Forestry Corporation, in collaboration with Universiti Malaysia Sabah

and Sabah Wildlife Department conducted two aerial surveys and limited boat surveys in 2000

and 2007 which provided a broad overview of marine mammal distribution in Sarawak (Bali et

aI., 2008). In addition to Irrawaddy dolphins, several researchers have confirmed the

occurrence of other types of cetaceans in the nearshore waters of Sarawak, including Indo­

Pacific fin less porpoises (Neophocaena phocaenoides) , Indo-Pacific humpback dolphins

(Sousa chinensis) and bottlenose dolphins (Tursiops sp.) (Beasley and Jefferson, 1997;

Jaaman, 2004; Bali et ai., 2008). Anecdotal reports from fishermen and dolphin watch tour

operators specifically from Kuching Bay provide further evidence that those species occur in

the same areas as the Irrawaddy dolphins. In 2008, the launch of the Sarawak Dolphin Project

(SDP) paved the way for more dedicated cetacean research in Sarawak. The research focused

on three sites in the first two years, namely the Kuching, Similajau and Miri regions. It aimed

to collect baseline data on seasonal distribution, habitat use and conservation needs of dolphins

in Sarawak, provide training and field experience for local Malaysian scientists, as well as to

raise awareness in the local communities by disseminating findings through scientific and

popular press, as well as community workshops (Minton and Peter, 2009). This thesis

embodies an important element of the project's first and second aims and uses data collected

during the project's first two years.

2

1.2 Rationale of study and hypothesis

In light of the vulnerable status of Irrawaddy dolphins in the IUCN Red List, there is an urgent

need to collect baseline data to assess the population status and design effective conservation

management plans.

This dolphin and other inshore cetaceans which rely on coastal waters continue to face

anthropogenic threats incfuding incidental capture in fishing gears, habitat degradation and loss

due to coastal developments, decreased fitness from pollution or contaminants as well as

depleted prey resources due to intensive fishing activities (Jaaman 2004; Jaaman et a!., 2009).

However, before threats can be mitigated, the distribution, habitat preferences and population

estimates of the animals in the area have to be scientifically investigated, mapped and

quantified. This information, along with definition of core habitats and the characteristics that

make them attractive to the dolphins can be used to advise conservation authorities and

managers. To date there is a lack of information on these topics, not only in Sarawak but

throughout the coastal range of this species. As such, this research will make a valuable

contribution to the understanding of this species throughout its range.

The first hypothesis for this study was that the Irrawaddy dolphins in Kuching Bay comprise

an estuarine-dwelling population that is distributed in relatively shallow areas similar to the

population occurring in the Bay of Bengal, Bangladesh (Smith et a!., 2008). If this hypothesis

was true, we would expect the dolphins to occur closer to shore as well as river mouths. This

study also hypothesized that water quality has a similar impact on habitat choice of Irrawaddy

dolphins in Kuching Bay as in the other regions, where they are known to prefer low salinity

waters that are highly turbid (Do lar et a!., 1997) with a constant input of freshwater. The final

3

hypothesis was that the population in the bay is small, and therefore more vulnerable to the

known threats in the area.

1.3 Research objectives

The first objective of this thesis was to map the distribution patterns of Irrawaddy dolphins in

the estuarine waters of Kuching Bay in order to test the hypothesis that the population here has

a similar distribution to that shown in other areas. Line transect boat surveys were conducted to

map the distribution and determine relative abundance within the study area. Then ArcGIS and

other statistical tools were used to analyse the relationship between sighting locations and

depth and distance to shore and river mouths.

The second objective was to further define the habitat preferences of Irrawaddy dolphins in

Kuching Bay in terms of water parameters including temperature, acidity (pH) and salinity.

Instruments were used to sample these water parameters and readings were compared with

Irrawaddy dolphins' encounter rates to look for possible associations between these physical

characteristics and dolphin distributions, and to determine whether there are any seasonal or

tidal changes in these parameters that are linked to dolphin distribution.

The third objective of the study was to obtain absolute abundance estimates of Irrawaddy

dolphins in Kuching Bay. This was achieved by using mark-recapture techniques on photo­

identified individuals to generate population estimates for the Kuching study area. This will

help to determine whether the population in Kuching Bay is indeed small and in need of

conservation measures.

4

Pusat I(hidmat Maidumat Akadenuh UNlVERSm MALAYSIA SARAWAK

The fourth objective was to learn about the individual movement patterns of the Irrawaddy

dolphins in Kuching Bay. This was attained by identifying individual dolphins through photo-

identification and plotting the locations of individuals that were observed on more than one

occasion. Information on the species' different locations in the bay over time would help better

understand their occurrence throughout the study area and determine individual ranging

patterns.

1.4 Thesis outline

Chapters I and 2 consist of a general introduction of the Masters research project and a

literature review regarding the study methods and the target species respectively. Chapter 3

focuses on cetacean sightings data that were collected during boat surveys conducted between

June 2008 and May 2010. This chapter also presents an analysis of physical characteristics like

depth, distance from shore, and distance to river mouths as well as water quality readings of

temperature, pH and salinity in relation to Irrawaddy distributions to further refine

understanding of the types of habitats that are preferred by the dolphins in Kuching Bay.

Chapter 4 discusses the results of photo-identification studies, including the ranging patterns of

individually identified Irrawaddy dolphins and the use of mark-recapture methods (through the

program MARK) to obtain absolute abundance estimates. Chapter 5 draws conclusions from

the results of the analyses from Chapters 3 and 4 to formulate research and management

recommendations for the future.

5

CHAPTER 2

Literature Review

1.1 Distribution of Irrawaddy dolphins in the region

Irrawaddy dolphins are patchily distributed, and limited to primarily estuarine, tropical and

subtropical waters in the Indo-Pacific from northeastern India east to the PhiIlipines (Smith,

2008). Freshwater populations of Irrawaddy dolphins have been well documented in the

Chilika Lake in India (Sutaria, 2009) and the Songkhla Lake in Thailand (Beasley et ai., 2002),

both completely or partially isolated brackish water bodies. The Chilika Lake is a brackish­

water, oblong-shaped marine appended lake which receives an influx of salt water from the

Bay of Bengal (Sutaria and Marsh 2011). In the lake, the distribution of Irrawaddy dolphins is

clumped in the central and southern sectors, as well as the outer channel of the lake but not in

the northern sector as it is shallow and weed-infested (Sutaria, 2009; Sutaria and Marsh, 2011).

Songkhla Lake, another marine appended lake which is situated in southern Thailand was

surveyed in May 200 I and February 2002 (Beasley et aI., 2002). They found that the

population here were restricted to the freshwater portion in the upper region of the lake

(Beasley et ai., 2002).

Additional populations have been documented and studied in the river systems of Southeast

Asia. In the Mahakam River and associated lakes in Kalimantan, Borneo, Irrawaddy dolphins

were sighted from approximately 90 km from the coast to as far as 600 km upstream (Kreb and

Budiono 2005a). This species' distribution in the Ayeyarwaddy River during the dry season is

located about 1,000 km from the sea and restricted to a 370-km segment of the river (Smith

and Than Tun, 2007). In the Mekong River, the range of the Irrawaddy dolphin is a 190-km

river segment located approximately 500 km upstream of the river mouth in Kratie, Cambodia,

6

to Khone Palls slightly upstream of the Lao PDR-Cambodia border (Beasley et aI., 2007). The

Malampaya Sound, Palawan has the only known population of the species in the Phillipines to

date (Dolar et aI., 2002; Smith et aI., 2004). In the first dedicated survey of the area, Dolar et

al. (2002) recorded 17 sightings during 230 km of search effort with a mean encounter rate of

7.4 dolphins per 100 km. Meanwhile, Beasley et al. (2002) recorded an average group size of

4.3 ± 2.9 (mean ± SO) with a sighting rate of 0.03 dolphins per km in Songkhla Lake,

Thailand.

While these riverine and marine appended lake populations have been relatively well studied,

few predominantly marine and coastal popUlations have been studied in any detail, with the

population inhabiting the Sundarbans mangrove forest of Bangladesh being one of the only

estuarine populations for which there is a popUlation estimate (Smith et aI., 2008). In the

coastal waters of East Kalimantan, Indonesia, Kreb and Budiono (2005b) observed the species

nearshore, and in deltas and bays with a combined mean encounter rate of 0.085 dolphin per

km. This species was observed once during a survey in the Mergui Archipelago, located on the

coast of southern Myanmar (Smith and Than Tun, 2008). In contrast to that, Irrawaddy

dolphins were frequently observed in the Bay of Bengal, Bangladesh with a total of 75 dolphin

groups detected on effort along 779.7 km of trackline (Smith et aI., 2008). Irrawaddy dolphins

were also recorded in coastal Cambodian waters by Beasley and Davidson (2007).

In East MaJaysia, the Irrawaddy dolphin is frequently sighted in inshore waters and is the only

species of dolphin found upstream in various river systems (Beasley and Jefferson, 1997;

Jaaman, 2006). In their brief visit, Beasley and Jefferson (1997) reported that the Irrawaddy

dolphins are common in several estuaries along the north coast of Borneo. Beasley (1998)

conducted a research trip in East Malaysia, which included the area covered in this thesis and

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