136 Chiang Mai J. Sci. 2015; 42(1)

Chiang Mai J. Sci. 2015; 42(1) : 136-147 http://epg.science.cmu.ac.th/ejournal/ Contributed Paper

Population Size and Habitat Patterns of Indo-Pacific Humpback Dolphins (Sousa chinensis) off Donsak, Surat Thani, Thailand Suwat Jutapruet*[a], Kongkiat Kittiwattanawong [b] and Siriporn Pradit [a] [a] Marine and Coastal Resources Institute, Prince of Songkla University, Hat Yai, Songkhla, 90110, Thailand. [b] Phuket Marine Biological Research Center, Phuket, 83000,Thailand. *Author for correspondence; e-mail: [email protected] Presented at the International Graduate Research Conference 2013 (IGRC2013), 20th December 2013, Chiang Mai, Thailand. Received: 24 December 2013 Accepted: 5 May 2014 ABSTRACT This study investigated the population size and distribution pattern of the Indo-Pacific humpback dolphin (Soasa chinesis) off Donsak, Surat Thani, Thailand. The field surveys were conducted along the coastline of the mainland and the offshore area of the Angthong Marine National Park. The population size was estimated by applying a mark-recapture model to the individual photo-identification records collected from field surveys. In total, 142 individuals were photo-identified using dorsal fin characteristics. The population size was estimated to consist of 160 individuals with a range of 152 - 178 at a 95% CI. Spatial (GPS data) and environmental information were recorded for distribution and habitat analysis. The most frequent encounters with humpback dolphins occurred, in decreasing order of magnitude, at Somserm Ferry, Raja Ferry, Som Island, Nok Ta Pao Island and Taled Bay. The present study showed that the humpback dolphins off Donsak were frequently found near the coast in close proximity to man-made structures, sea grass areas and mudflat habitats. Our study revealed that a distinct humpback dolphin habitat occurred at a specific off-shore distance, water depth and water transparency. Results of this study improves the better understanding of the humpback dolphin’s ecology and offers informed baselines essential for meaningful marine-mammal protection and management policies in the Gulf of Thailand.

Keywords: population size, Indo-Pacific humpback dolphin, Donsak-Surat Thani, habitat patterns

1. INTRODUCTION The richness of complex marine and activities that consists of Donsak estuary, coastal ecosystems attracts human activities small islands, sea grasses beds, muddy beaches, which have caused marine and coastal mangroves, rocky shores, sandy beaches, habitat degradation and loss of natural rocky cliffs, headlands, coastal communities, resources [1]. The Donsak, Surat Thani, artisanal fishery, commercial fisheries, ferry Thailand is a complicated ecosystem with transportation piers, resorts and hotels, plentiful natural resources and anthropogenic manufacturing industries and famous Chiang Mai J. Sci. 2015; 42(1) 137

dolphin-watching tourism. Dolphin-watching dolphins (Unpublished data). In consequence, tourism industry exclusively targeting to the the humpback dolphin research in Thailand Indo-Pacific humpback dolphin, Sousa chinenis, is a critical need. Moreover, information was promoted to motivate tourism activities about stranded dolphins was collected along the coastlines of the Donsak district, along the coastline of the Gulf of Thailand Surat Thani province and Khanom, Nakhon (Unpublished data). However, dolphins are district, Si Thammarat province [2]. frequently found in the boundary areas Although many efforts were made for between Donsak, Surat Thani and Khanom, marine and coastal conservation policies, Nakhon Si Thammarat. Although there are anthropogenic overexploitation is still no tourism activities in the Donsak area, increasing. More information is needed to Indo-Pacific humpback dolphins inhabiting improve the effectiveness and scientific this shoreline may also form part of the basis of current conservation policies. dolphin population of the Khanom area. Data on the baseline dolphin population, A previous study identified 33 adults, including distribution, abundance and eight juveniles and eight calves with a habitat characteristics, are still very rare estimated population estimate of 49 dolphins across South-East Asia, a region considered (with no confidence interval) in the Khanom to be one of the important habitat for Sea, Nakhon Si Thammarat [2]. The current humpback dolphins. Scientific research is an study was conducted at Donsak, Surat Thani, important measure to provide essential north of the adjacent area, Khanom, baselines and must be included in the marine Nakhon Si Thamarat during a longer period conservation issues [3, 4]. The International and include distribution and habitat Union for Conservation of Nature (IUCN) characteristics of humpback dolphins. It is categorized the Indo-Pacific humpback hoped that the data generated by this study dolphin as a near-threatened species [5]. would lead to improved decision-making Not only are humpback dolphin population on humpback dolphin conservation by size information mentioned in the IUCN stakeholders in Donsak District, Surat Thani, report is needed, but also supportable habitat Thailand. quality information [6]. Although the humpback dolphins are currently known due 2. MATERIALS AND METHODS to dolphin shows (Oasis Sea World, 2.1 Study Site Chanthaburi, Thailand) and dolphin watching 2.1.1 Coastal area (CA) tourism in Khanom, Nakhon Si Thammarat, The study was conducted in the coastal Thailand, there is still a lack of understanding zone of Donsak district, Surat Thani province about population, habitat or general and Khanom district, Nakhon Si Thammarat information of humpback dolphin in the province, the east coast of Southern Thailand Thailand region. Marine and Coastal Resources (Taled Bay-TB, Thong Nian Bay-TNB, Research Center (MCRC), Central and Lower Lak Sor Mountain-LSM). The area is Gulf of Thailand have recorded an increase characterised by rocky shores, sandy beaches, in the mortality rate of humpback dolphins rocky cliffs, mud flats, mangroves and sea during the period 2006-2012 (Unpublished grass beds (Tarai island, TRI) (Figure 1). data). In the gulf of Thailand, the bycatch Human activities such as the Somserm Ferry, mortality rate of humpback dolphins was Sea Tran Ferry, Raja Ferry Transportation piers recorded as 24% of 62 stranded humpback (to the famous tourism islands, Samui 138 Chiang Mai J. Sci. 2015; 42(1)

Island, Pha-ngan island), coastal fishery, Marine National Park. The protected marine dolphin watching tour activities, industrial navy base, the Gulf of Thailand, was factories are also found within this area. converted into a marine national park on 12th November 1980 due to the abundant 2.1.2 Offshore area (OA) species and natural marine resources [7]. The small islands of Ri Gun Island (RGI), This Ang Thong Marine National Park Nok Ta Pao (NTPI), Som (SI), Chuek (CI), consists of 42 small islands with dry evergreen Pa-luai (PLI) Pi Island (PI) and Jae Island (JI) forests, beaches, and lime stone and mangrove are located at the north of Donsak coastline. forests [7] (Figure 1). A part of Pa Luai Island is the Ang Thong

Figure 1. Study area, Donsak, Surat Thani, Thailand. %: Som Serm Ferry, Seatran Ferry and Raja Ferry respectively.

2.2 Data Collection (WD), water transparency (SD), pH, sea 2.2.1 Boat surveys surface temperature (SST) salinity (SN) and Boat-based surveys were conducted Beaufort Sea State category were recorded at from between December 2011 - April 2013 the dolphin encounters. Further environmental during 08:00-14:00 with Beaufort Sea State conditions were recorded, noting tide (TD, category category between 0 and 2 off the 0 being low tidal and 1 being high tidal), coast of the Ang Thong islands of Donsak, cloud cover (CC, 0 being clear sky with <20% Surat Thani Province. A long-tailed fishing cloud cover, 1 between 20%-50% cloud boat with an outboard 175 hp engine was cover and 2 being > 50% cloud cover), used with speeds not exceeding 15 km/h. wind power (WP, 0 being no wind blow, 1 as Route tracking was recorded by GPS little wind blow and 2 being strong wind), (Garmin eTrex30) and the positions were rainy (RN, 0 being no rain and 1 being rain) marked when dolphin were sighted. The and sun light (SL, 0 being no sun shine and boat speed was slowed when dolphins were 1 being sun shine) conditions. A variable, encountered. We measured water depth “Seasonal change” was noted with May 16 Chiang Mai J. Sci. 2015; 42(1) 139

to January 31 was categorized as the Rainy during the study, or, alternatively, as the Season and February 1 to May 15 as the total number of animals ever sighted in the Summer Season. Habitat characteristics of sampled area between the first and last dolphin encounter sites were recorded as periods of the study [9]. The parameter Φ rocky shore (RS), man-made structure (MM), denotes apparent survival rate, P denotes mud flats (MF), sandy beach (SB) and sea grass the probability of capture, and b denotes beds (SG), and were abbreviated by RS, the probability that an animal from the super- MM, MF, SB and SG, respectively. Finally, population will enter the subpopulation distance off the shore (DS) was measured (subpopulation referring to the animals (meter) with the perpendicular straight line occurring in the study area). from nearest coastline to the encoutered position by GIS software. Variance of N was estimated using the delta method and the following equation: 2.2.2 Photo-identification Researchers attempted to photograph all the individual dorsal fins in a group that where n is the total number of dorsal were the most perpendicular to the dolphin’s fins from which θ was calculated. Confidence body axis with DSLR D80 D90 and D7000 intervals for N assumed the same error Nikon digital cameras with 70-300 mm total distribution as the mark-recapture estimates lenses. The processing of utilised 45,000 [10]. The population size was computed pictures that were selected based on the most by Parm-Specific as a Link function, Sin clearest dorsal fins. Though a systematic were Φ and P, mlogit (1) was b and logit process individuals were indentified and was N on POPAN parameterization model added to the catalogue by recording the option in MARK software. presence of nicks, notches, pigmentation patterns, color, dorsal fin edge figure, scar 2.4 Habitat Characteristic or wound. The datasheet was replaced with Habitat characteristics were tested 0 and 1 to indicate either absence or presence statistically by using Principal Component of each individual per sighting. Analysis (PCA) and Canonical Correlation Analysis (CCA) analysis using R software 2.3 Data Analysis and ade4 [11] and vegan library packages 2.3.1 Abundance [12]. We categorized each sighting with The researchers recorded 89 sightings environmental factor, season, habitat events from all surveys conducted over characteristics, inshore and offshore area, 17 months of. A dolphin sighting matrix and the encountered area names. data set was constructed with the occurrence of each individual per site and the 3. RESULTS AND DISCUSSION population size was estimated by live 3.1 Survey Effort recapture of open population model Forty-seven boat survey-days (205 h) parameterization on POPAN in MARK were undertaken, covering a total distance Software [8] which includes the parameter of 2,618.4 km. The surveys resulted in N - the size of a superpopulation. N can be 89 dolphin sightings within the 17 months. thought of as either the total number of The cumulative sightings of humpback animals available for capture at any time 140 Chiang Mai J. Sci. 2015; 42(1)

dolphins in the study area are indicated in from the 17-month survey (Figure 2). At Figure 3. Solitary individuals comprised least 15 individuals were identified as the 14.6% of all sightings. The highest frequency same individuals from a previous study [2]. of occurrence was found in the first The average group size of humpback five areas, Som Serm Ferry, Raja Ferry, dolphins sighted in this study ranged Som Island, Nok Ta Pao Island and Ta Led between from two to eighteen dolphin with Bay (Figure 3). The dolphins were encountered the average group size 4.72 ± .35 based on off-shore in 22.5% of all sightings. 455 individuals recorded for the full study. Solitary individual were observed in 10.34% 3.2 Population Size of all sightings. A total of 160 individuals Total 142 humpback dolphins were was observed with a range of 152 - 178 at identified. These individuals were separated 95% CI from POPAN paramiterization on by age class from all 47 observation days MARK software.

Figure 2. Survey of Indo-Pacific humpback dolphin in the Donsak area. AD = adult; SA = sub-adult; JN = juvenile; CV = calf.

Figure 3. The frequency of encountered positions of humpback dolphin in the study area, SSF - Som Serm Ferry, RF - Raja Ferry, SI - Som Island, NTPI - Nok Ta Pao Island, TLB - Taled Bay, RGI-Ri Gun Island, STF - Sea Tran Ferry, TRI - Ta Rai Island, PLI - Pa Luai Island, CPI - between Chuek and Palui Island, PI - Pee Island, JI - Jae Island. Chiang Mai J. Sci. 2015; 42(1) 141

3.3 Habitat Characteristics and Pi Island (PI) (Figure 4, 5). The rocky shore In 83 of the 89 sightings the (RS) and sandy beach (SB) were surrounded environmental parameters were measured with two ellipses that were not overlapped because five of all sighting were bad weather on mud flat (MF), mam-made structure conditions. The PCA analysis showed the (MM) and sea grass beds (SG) (Figure 6). groups of habitat characteristic. The ellipses The partial overlapped of two ellipses surround the group of environmental between rainy and summer seasons were parameters that were categorized with shown on Figure 8. The PCA of dolphin encountered position, coastline and offshore, encountered position on Figure 4 are habitat characteristics and season. The offshore Environmental parameters of dolphins islands, Jae Island (JI), Pa Luai Island (PLI), encounter were analyzed in the groups of the area between Chuek and Paluai Island data by using CCA analysis with R software (CPI), Som Island (SI) and Nok Ta Pao Island (Figure 8). (NTPI) were seperalately grouped from The DS, WD and SD were significantly encoutered position on coastline, Sea Tran different from the habitat characteristics of Ferry (STF), Som Serm Ferry (SSF), Raja Ferry humpback dolphin population in study (RF), Ta Rai Island (TRI), Ta Led Bay (TLB) area (Table 1).

Figure 4. Principle component anlaysis of encounter positions of dolphins. Som Serm Ferry (SSF), Raja Ferry (RF), Som Island (SI), Nok Ta Pao Island (NTPI), Taled Bay (TLB), Ri Gun Island (RGI), Sea Tran Ferry (STF), Ta Rai Island (TRI), Pa Luai Island (PLI), between Chuek and Palui Island (CPI), Pee Island (PI) and Jae Island (JI). 142 Chiang Mai J. Sci. 2015; 42(1)

Figure 5. PCA anlaysis of coastline and offshore data from the dolphin study areas.

Figure 6. Principle component analysis of habitat characteristics of dolphins (RS: Rocky shore, SB: Sand beach, MF: Mud flat, MM: Man-made structures and SG: Seagrass area). Chiang Mai J. Sci. 2015; 42(1) 143

Figure 7. Principle component analysis of seasonal data of dolphins.

Figure 8. Canonical correlation analysis from R software, Distance of the shore (DS), Water depth (WD), Water transparency (SD), Sea surface temperature (SST), Salinity (SN), Tidal (TD), Cloud cover (CC), Wind power (WP), Sun light (SL), Rain (RN), Beaufort sea state category (BF). 144 Chiang Mai J. Sci. 2015; 42(1)

Table 1. Range, Mean (± SD) and canonical correlation analysis of environmental parameters of humpback dolphins. Factors Range Mean ± SD CCA r2 Axis1 Axis2 DS (m) 17-2976.73 468.21±603.06 -0.633 -0.774 0.2692*** WD (m) 1.70-16.40 4.92±2.73 -0.999 0.037 0.4884*** SD (m) 0.5-3 1.27±0.61 -0.999 0.019 0.4243*** SST ( c) 26.60-32.60 29.95±1.38 -0.920 0.392 0.0126 pH 7.15-9.07 8.22±0.31 0.257 0.967 0.0101 SN (ppm) 25-35 30.22±2.28 0.987 0.163 0.0366 TD 0-1 0.67±0.47 -0.523 0.852 0.0509 CC 0-1 0.08±0.28 0.549 0.836 0.0187 WP 0-1 0.35±0.48 0.727 0.686 0.0150 SL 0-2 1.65±0.57 -0.927 0.375 0.0662 RN 0-1 0.02±0.11 0.368 0.930 0.0187 BF 0-2 0.33±0.50 0.999 0.051 0.0063 Significance codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1, Distance of the shore (DS), Water depth (WD), Water transparency (SD), Sea surface temperature (SST), Salinity (SN), Tidal (TD), Cloud cover (CC), Wind power (WP), Sun light (SL), Rain (RN), Beaufort sea state category (BF) 3.4 Population Size Our results of 160 (152 - 178) Donsak 3.5 Habitat Patterns humpback dolphin population estimation is Our study showed that Indo-Pacific a small population based on the 89 sightings. humpback dolphins in the Donsak area The recommended sighting numbers to have some unique habitat characteristics. estimate population on capture-mark- We found that the Donsak dolphins inhabit recapture model is 60 sightings [12]. Our the coastline within 0.47 - 2.9 km off shore, study gives a larger humpback dolphin at an average depth of 4.9 m and water population size estimate than that previously transparency < 3.0 m which supports the obtained at the east coast of Gulf of previous findings of humpback dolphin Thailand [2]. Moreover, 15 of the humpback habitat characteristics [16, 17, 18, 19 and 20]. dolphins were previously detected [2] in the From the present study, an analysis of overlap area, from Raja Ferry piers to Thong environmental factors (Figures 4-7) indicates Nian Bay in this study were previously that high densities of dolphins occur in detected. This does provide evidence of inshore areas (mud flats, seagrass areas close larger scale movement between research to man-made structures) as opposed to off areas and further supports a larger dolphin shore island groups. Humpback dolphins population in the study area due to further may be found all year round without seasonal ranging individuals [13, 14]. Comparing differences in numbers. However, different sub-populations estimates from known groups of dolphins occur during the summer population sizes throughout Sousa range, and rainy seasons. (Figure 7). Nevertheless, the humpback dolphin population size in our results show significant differences of Thailand might be similar to the Moreton Bay, habitat characters in humpback dolphins Australia and Great Sandy Strait, Australia (Distance of the shore, water transparency population estimates (see Table 2). and water depth). Chiang Mai J. Sci. 2015; 42(1) 145

Table 2. Population size and abundance estimates for Indo-Pacific humpback dolphins1 [1, 15]. Rank Populations Areas No. 1. Pearl River Estuary China 2552 2. Hong Kong + adjacent area China 1028 3. Goa Bay India 842 4. Algoa Bay South Africa 466 5. Leizhou Bay China 237 6. Gulf of Kachch India 174 7. Richards Bay South Africa 166170 8. Moreton Bay Australia 163 9. Great Sandy Strait Australia 150 10. Moreton Bay Australia 119 11. Dafengjiang River China 114 12. Maputo Bay Mozambique 105 13. Eastern Taiwan Strait Taiwan 9985 14. Xiamen China 86 15. Xiamen China 76 16. Zanzibar (south coast) East Africa 63 17. Cleveland Bay Australia 54 18. Khanom Thailand 49 19. Hepu China 39

3.6 Implications for Conservation facing these threats in the Donsak area. It is hoped that current and future marine Som Serm Ferry is adjacent to the Donsak conservation policies will help the populations estuary where humpback dolphins are of the Indo-Pacific humpback dolphin to predominantly encountered and there is increase. Adjacent areas to the study site evidences showing that dolphins forage include the Ang Thong Marine national park, times overlap with coastal fishermen work Moo koh Tha Lae Tai Marine Protected leading to a high risk of entanglement. area, Corporate Social Responsibility (CSR), This study provides us with a better mangroves area, seagrass area and dolphin understanding and insight about humpback watching tourism which promote dolphins dolphin ecology which can directly guide conservation and awareness in coastal marine and coastal resources management communities [23]. However, at present, there for the dolphin conservation in Thailand. are no specific data suggesting that protected At the same time, longer-term studies on areas can improve dolphin reproduction. population trends and impact of marine Unfortunately, humpback dolphin populations anthropogenic threats to dolphins are all around the world has been shown to be required to reach a science-based dolphin decline [5] due to many threats such as abundance assessment. overfishing, accidental take during fishing for other species, pollution, vessel traffic 4. CONCLUSION and wildlife tourism [6]. The present study The population size and habitat pattern suggests that humpback dolphins are also of Indo-Pacific Humpback Dolphin are of 146 Chiang Mai J. Sci. 2015; 42(1)

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