Volume 2, Number 2, July-December 2014

POPULATION STATUS OF IRRAWADDY DOLPHIN, Orcaella brevirostris (OWEN IN GRAY, 1866) ALONG THE AYEYAWADY RIVER

Dr.Naing Win and Dr.Si Si Hla Bu Department of Zoology, Yadanabon University, Myanmar

ABSTRACT KEY WORDS The mean num ber of O. Irrawaddy dolphin, population status, brevirostris per group, based on be st Ayeyawady River group s ize estimated, was 5.5 ( SD = 3.7, Range = 1 -13) and t he ove rall encounter rate was 0.10 dolphins/km INTRODUCTION from June 2008 to May 2009. It was Ayeyawady River is the main 5.2 (SD=2.58, Range=1-10) w ith t he transport system f or t he c ountry a nd overall e ncounter rate w as 0.14 measures about 2170 km f rom i ts dolphins/km from J une 2009 t o May origin t he river c onfluence Maykha 2010. T he number s lightly reduced and M aylikha t o t he r iver m outh with 4.9 ( SD = 2.94, R ange = 1-12), (Smith a nd M ya Than T un, 2007). but the o verall en counter r ate w as Since the A yeyawady R iver w as 0.18 dol phins/km from J une 2010 to known as Irrawaddy River in the past, May 2011. T he ove rall results Irrawaddy dol phin i s internationally indicated t hat they w ere encountered recognized for Irrawaddy River. in small g roups a nd s eldom in aggregations. The m ean popul ation Irrawaddy dol phin, O. brevirostris size f rom J une 2008 t o M ay 2009 is di stributed i n va rious habitats was 14-16 individuals based on direct including shallow c oastal w aters of count method i ndicating 22.22% of the tropical a nd s ubtropical m arine the t otal population e xisted along waters of t he I ndo-Pacific, n orthern Ayeyawady R iver from M ingun to Australia, f reshwater lake an d river Banmaw. It r anged of 16 -18 systems o f t he M ahakam, A yeyawady individuals representing 25% of total and Mekong R iver System of L aos, population from J une 2009 t o M ay Cambodia, and Vietnam. The animals 2010, w hile 18 -22 i ndividuals were in n orthern Australian w aters are accounted from J une 2010 t o M ay morphologically d istinct f rom those 2011 amounting to be 25.28 % of the in Asia ( Beasley, Arnold a nd H ein- total population. sohn, 2002) . International W haling Commission ( 2001) r eported dr amatic declines i n r ange a nd a bundance of

77 Volume 2, Number 2, July-December 2014 the Mekong and Mahakam freshwater Malampaya S ound (Dolar et al., populations. I ncidental m ortality i n 2002). In fact, there are no organized fisheries s uch a s g illnets, explosives fisheries for this species, but isolated is lik ely th e p rincipal c ause o f instances o f t argeted k illing have depletion, a lthough the de gradation been reported. Irrawaddy dol phins i n of r iver an d lake s ystems cau sed by Lao P DR ar e o ccasionally cau ght i n damming, f orestry pr actices, a nd fishing gear ( Baird a nd M ounsou- mining c ould a lso pl ay a n i mportant phom, 1994). role ( Reeves, S mith, Crespo a nd di A num ber of s urveys have Sciara ( 2003). I n A yeyawady R iver, been c onducted since 199 6 t o a ssess the researchers i dentified acci dental the a bundance of t his s pecies i n the entanglement in g illnets a nd Ayeyawady River. H owever, l ess poisoning from mercury, as potential attention ha s be en de voted t o t heir threats t o t he population ( Smith and conservation needs compared to other Jefferson, 2002). I rrawaddy dol phin cetaceans. I n 2005, t he Ayeyawady becomes a C ritically Endangered Dolphin P rotected A rea w ithin a 74 species as cl assified i n I UCN R ed km s tretch of r iver be tween M ingun List (2004). and K yaukmyaung w as established Estimates of p opulation s ize by the Department of Fisheries (DoF) are an i mportant as pect o f t he cooperated with the Wildlife Conser- ecology of a ny s pecies, a nd an vation Society ( WCS). R esearch integral p art in the ma nagement of approach h as s o f ar m ainly concen- wildlife p opulations. T he estimation trated on the population status of the of s ustainable r emoval l evels of dolphins. In or der to e fficiently pr otect animal populations r equires know ledge Irrawaddy dol phin f rom a ny t hreats of abundance es timates an d t heir caused by hum an di sturbance, dol phin variances ( Wade, 1998) . R ecent Protected Area (PA) was successfully studies on freshwater populations of established al ong A yeyawady River Irrawaddy dol phins t hroughout between Mingun a nd K yaukmyaung. Southeast A sia r evealed popul ations It is a imed to promote th e p ublic that number in the tens of animal, all awareness and monitor t he effective- facing p otential extinepation i n the ness of protective m easures for near f uture (Beasley et al., 2002, conservation of t his threatened Kreb, 2002, Smith et al., 2003). species not only in the vicinity of PA but a lso i n the ot her distribution Similarly, Irrawaddy dolphins ranges in Myanmar. have b een r ecorded as accidentally killed in g illnets in th e Mekong

(Baird and M ounsouphom, 1997) , Mahakam r ivers ( Kreb, 2002), MATERIALS AND METHODS Songkhla ( Beasley et al., 2002) a nd The u pper reaches o f the Chilka Lake (Dhandapani, 1995) and Ayeyawady be tween M ingun a nd 78 Volume 2, Number 2, July-December 2014

Kyaukmyaung ( 74km) i s t he study RECORDING GROUP SIZE AND area, which is also the area where the ENCOUNTER RATE dolphins a re pr otected ( Fig.1). D ata Based on t he r ecorded collection dur ing J une 2008 t o May sightings, g roup s ize of dol phin was 2011. The m aterials used dur ing the estimated as best, high and low group study a re a pa ir of 7x 50 bi noculars, size in terms of the consensus of the global positioning s ystem ( GPS 72) observers on t he w atch a ccording to and C annon E os 40D c amera with Smith (2002). T he pos ition of e ach 400 m m zoom lens. T he s tudy was sighting was recorded by GPS from a conducted by a c ontinuous visual distance of 50m from t he specimen. survey on dolphins in the Ayeyawady Normally two t rips w ere t aken each River between Mingun and Kyaukm- month f or monitoring a nd recording yaung using a local motorised vessel. the num ber of s ightings, how ever, Interview s urvey t echnique, which schedule had t o be c hanged w ith based on a questionnaire, w as a lso respect to cl imatic and v isual co ndi- utilized. B oth i ndividual in terviews tion of the study area. Encounter rates and group discussion were carried out were calculated from total number of at th e f ield s ites. D uring sightings observed dolphins di vided by t he search effort a nd t he num ber of number of kilometers of r iver le ngth dolphins w ere r ecorded a nd phot o- searched by us ing di rect count graphs w ere also t aken. While method followed after Kreb (1999). recording the num bers of dol phins, handheld 7x50 binoculars were aided. The l ocations of dol phin sightings DOLPHIN SIGHTING RESULTS were r ecorded w ith a G lobal Positioning S ystem ( GPS). Search During t he s tudy pe riod f rom effort w as car ried out b y three June 2008 t o M ay 2011, dol phin observers taking pos ition at t he bow groups were sighted. The variation on of t he v essel; one t aking pos ition a t the maximum and minimum sighting the port (left), one at starboard (right) was recorded. In the first study year, and one in the center. Duration of 30 June 2008 to M ay 2009, t otally 39 minutes w as a llotted t o e ach pe rson sightings, was r ecorded. A pril 2009 for r ecording t he s ightings, after showed the highest sighting (9) while which the pos ition of e ach pe rson the lowest was recorded in June 2008 was c hanged unt il each pe rson has (2). I n t he second s tudy y ear from logged 1 hour 30 minutes each. This 2009 June to May 2010, 41 s ightings was followed by t wo hour s br eak t o were r ecorded. T he hi ghest w as reduce f atigue; however car e w as revealed in November and December taken to ensure that dolphins are not 2009 (11 e ach) w hile the l owest i n missed dur ing r otations. T he c enter May 2010 (1). In the third year study person or a nother person w as assigned (June 2010 t o May 2011) , total to record the sighting data. sighting was 59, i n w hich F ebruary 79 Volume 2, Number 2, July-December 2014

2011 w as r ecorded as t he highest a total of 1551.58 km were surveyed sighting ( 13) a nd O ctober 2010 w as during 238 hours of search effort with the lowest ( 2) ( Fig. 2). I n g eneral, an average speed of 6.4 km/h. It was dolphins w ere f requently exposed recorded to be 59 sightings of dolphin along the s tudy r oute dur ing t he groups f or a t otal e stimate of 293 period of l ow w ater level i n dr y (best), 311 ( high), and 288 ( low) season whereas t he low sighting was dolphins i n t he protected a rea. The noticed during monsoon. mean num ber of dol phins per group, based on be st g roup s ize es timates, was 4.9 ( SD = 2.94, R ange = 1-12). GROUP SIZE AND ENCOUNTER The overall e ncounter r ate w as 0.18 RATE dolphins/km (Fig.3C, D).

During June 2008 t o M ay

2009, it was recorded to be a total of 2137.4 km dur ing 250 hour s of POPULATION SIZE search effort ( average s peed = 8 .5 A popul ation size r anged of km/h). D uring t he e ntire s urvey, 14-16 individuals ba sed on t he s um while actively searching for dolphins of best g roup s ize e stimates dur ing it was recorded to be 39 sightings of patrol s urveys c onducted between dolphin group f or a t otal e stimate, Mingun a nd K yaukmyaung f rom 216 (best), 230 ( high), and 213 (low) June 2008 t ill May 2009 i ndicating dolphins i n t he protected a rea. The that 22.22 % of t he t otal population mean num ber of dol phins per group, exists al ong Ayeyawady R iver. Of based on be st g roup s ize e stimated, total i ndividuals r ecorded, 1-3 was 5.5 ( SD = 3.7, Range = 1-13). individuals of calf dolphins included. The o verall encounter r ate was Slight increase number was observed 0.10dolphins/km (Table 1) ( Fig.3A, in the following study year from June B). 2009 t ill M ay 2010 w ith popul ation In t he second y ear, a t otal o f size ranging of 16 -18 i ndividuals 1436.03 km dur ing 209.16 hour s of including 1 -2 i ndividuals of c alf search effort ( average s peed = 6 .8 which represented 25% of t he t otal km/h) w as r ecorded. D uring t hat population e xists a long Ayeyawady period, 41 s ightings of dolphin group River. A ccording t o t he s ubsequent for a total estimate of 214 (best), 217 year f rom J une 2010 till M ay 2011, (high), a nd 215 (low) dol phins were population s ize r anging of 18 -22 observed i n t he protected ar ea. The individuals based on the sum of best mean num ber of dol phins per group, group size es timates w as r ecorded. based on be st g roup s ize e stimates, This figure indicated that 25.28 % of was 5.2 ( SD = 2.58, R ange = 1-10). the t otal popul ation e xists along The overall e ncounter r ate w as 0.14 Ayeyawady River. The calf observed dolphins/km. During third year study, was 1-3 individuals.

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THREATS TO IRRAWADDY DOL- a total of 1063 fishing gears were PHIN IN PROTECTED AREA documented in the protected area. According to the survey from Listed in order of frequency, the June 2008 t o M ay 2011, a t otal of different types of gear were beach five dolphin deaths were recorded i n seine nets (20), bamboo traps (175), the pr otected a rea. I n 2009, t hree cast nets (27), drifting gill nets (509), dolphins died by e lectricfishing a nd fishing fence (107), fixed gill nets gillnet e ntanglement. I n 2010 and 2011, t wo dol phins death w ere (97) and long lines (128) (Fig.7). recorded by electric-fishing (Table 2) Illegal electrofishing was also infre- (Fig.4, 5, 6 ). quently recorded during the study period. Five instances electrofishing were observed in the first study year, FISHING GEAR CENSUS four in the second study year and five During t he entire c ourse of in the third study year. study from June 2008 to May 2011,

Figure 1. A map of study area between Mingun and Kyaukmyaung (Protected Area) Source : WCS

81 Volume 2, Number 2, July-December 2014

Table 1. Encounter rates of Irrawaddy Dolphins as observed per km of protected areas during June 2008 to May 2011.

Source: Original Research

Table 2. Dolphin deaths during 2009 to 2011 in the protected area.

Source: Original Research

Figure 2. Search efforts for Irrawaddy dolphin sighting on monthly base from June 2008 to May 2011

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(A) (B) Frontal view of the dolphin Side view of the dolphin

(C) (D) Group size of five dolphins Group size of four dolphins

Figure 3. Group of Irrawaddy dolphin, Orcaella brevirostris

83 Volume 2, Number 2, July-December 2014

(A) (B) Head part Side view

Figure 4. Carcass of juvenile female Irrawaddy dolphin, Orcaella brevirostris by electric fishing near Sein Pan Gone (May 2009)

(A) (B) Juvenile female dolphin Adult female, a victim of gillnet victimized by electric shock, near entanglement, near Hsithe Shinemaga (November 2009) (July 2011)

Figure 5. Carcasses of Irrawaddy dolphin, Orcaella brevirostris near Shinemaga and Hsithe

84 Volume 2, Number 2, July-December 2014

(A) (B) Collection of oil from Irrawaddy Fishing boats with illegal electric dolphin carcass device at Myayzun

Figure 6. Causes of threats to Orcaella brevirostris

Figure 7. Number of fishing gears set in the protected area during June 2008 to May 2011

DISCUSSION the A yeyawady R iver, Smith et al. During the survey of dolphins (2002) r eported 14 s ightings of dolphin g roups. A mong 59 c etacean between Mandalay an d B anmaw i n sightings r eported by Dolar et al 85 Volume 2, Number 2, July-December 2014

(2002) dur ing t he ve ssel s urvey i n second y ear, be st g roup s ize Malampaya S ound, P hilippines, onl y estimates, was 5.2 (SD ± 2.58, Range 17 sightings of I rrawaddy dol phins = 1 -10) w hile i n third y ear s tudy, i t were i ncluded. C oncerning O. was 4.9 ( SD ± 2.94, Range = 1-12). brevirostris from M yanmar w aters, In the comparison of the group size in Smith et al. (2002) r eported t he Myanmar an d o ther ad jacent countries, overall e ncounter r ate to be 0.16 it seems to vary that the group size of dolphins/km dur ing t he s urvey be tween Irrawaddy dolphin i n M yanmar i s Mandalay an d B anmaw. A gain, its larger t han t hat of ot her c ountry encounter rate w as obs erved t o be records 0.07dolphins/km also between Mandalay If the population within PA is and Banmaw by Smith et al. (2005). concerned, dur ing t he 2006 census In t he pr esent work, t he encounter conducted by Aung Myo Chit (2008), rate was 0.10 dolphins/km in the first the r esults r evealed t hat t he study y ear, 0.14 dol phins/km i n t he population s ize estimates o f the second study y ear a nd 0.18 Irrawaddy dol phin w as 18 -20 i ndi- dolphins/km in the third study year in viduals indicating 27.4% of t he t otal the Protected A rea b etween M ingun population ( 72 dol phins) e xisted and K yaukmyaung. B ased on these along the A yeyawady R iver, T he data, it was made known that dolphin present s tudy revealed t he mean population increased in the Protected population s ize t o be 14 -16 i ndi- Area compared to the above detection viduals indicating 22.22% of the total by previous authors. population during June 2008 t ill May Smith et al. (2002) r eported 2009. It r anged 16 -18 i ndividuals that the best group size estimates was representing 25% of t otal popul ation 4.2 (SD ± 3.80, Range= 1-15) during from J une 2009 t o M ay 2010 while Mandalay and B anmaw. I n M ekong 18-22 individuals ba sed on t he s um River, g roup s ize of Irrawaddy of best g roup s ize e stimates i n J une Dolphin r anged f rom 1 -7, w ith a 2010 t ill M ay 2011 w hich indicated mean of 3.02 a s doc umented by that 25.28 % of t he t otal population Stacey an d H vcncgaard ( 2002). exists along Ayeyawady River. Smith et al. (2006) a lso f ound the Similarly, Kreb, B udiono a nd mean g roup s ize of I rrawaddy Syachraini (2007) reviewed the status Dolphin to be 2.3 (SD ± 1.36, R ange of Irrawaddy dol phins i n t he = 1 -6) i n w aterways o f t he Mahakam R iver in I ndonesia and Sundarbans M angrove F orest i n reported t hat, annual m ortality a nd Bangladesh. D uring June 2008 to causes of t hat w ere mainly d ue t o May 2009 unde r s tudy, t he m ean their entanglement in gillnet and also number of dolphins per group, based by electro f ishing. E lectric f ishing is on best group size estimated, was 5.5 also popul ar i n us ing a long A yeya- (SD ± 3.70, Range = 1-13). I n the wady River because the equipment is 86 Volume 2, Number 2, July-December 2014 relatively in expensive, n eeds little On the whole, it was disclosed maintenance, and results in relatively that dol phin popul ation s lightly large catches with little effort. increases not only in the PA but also along t he river s egments of During the pr esent s tudy Ayeyawady af ter es tablishment of course, a s ingle m ortality o ccurred PA. R egular collaborative pa trols of due t o el ectric s hock n ear S ein P an DoF a nd W CS ha ve pr omoted the Gone in May 2009. The one that got public a wareness f or conservation killed by e lectric s hock w as young strategy by c onducting educational female dol phin. A gain, a nother outreach act ivities, en forcement on juvenile female dolphin recently died illegal f ishing t echniques a nd by el ectric shock n ear Shinemaga monitoring of dolphin s tatus which during July 2011. O verall, a t otal of might t hen i ncrease t he dol phin 13 dolphin deaths between 2002 and population along Ayeyawady River. 2009 a long A yeyawady R iver within the area of B anmaw a nd M ingun were reported by Mya Than Tun and Aung M yo C hit ( 2010) a lthough ACKNOWLEDGEMENT death of f ive dol phins w ere The f irst author i s deeply documented during t he course of t he indebted to R ector Dr K hin M aung study in PA. Oo, P ro R ector Dr M aung Maung Naing, Yadanabon U niversity f or giving u s p ermission to s ubmit th is CONCLUSION paper. Deep t hanks a nd g ratitude g o to Dr Khin May N yo, P rofessor a nd The present records of sightings Head o f D epartment, D epartment o f during the s tudy pe riod s howed Zoology, Y adanabon U niversity a nd impressive num ber c ompared t o t he Dr. M ie M ie Sein, P rofessor and previous records. I n the f irst s tudy Head of t he D epartment of Zoology, year (June 2008 to May 2009), totally Mandalay University for their interest 39 sightings were accounted in April and encouragement. I wish to express 2009. In t he s econd year f rom 2009 my g ratitude to U A ung M yo Chit, June t o M ay 2010, 41 s ightings was Humphrey Fellow, I rrawaddy D olphin also r ecorded w hile i n t he t hird year Co-ordinator, W ildlife Conservation study (June 2010 t o May 2011), total Society (WCS) f or hi s pr ecious sighting was recorded to be 59 in the guidance a nd a iding me i n various protected area. This variation may be ways whenever r equired i n t he f ield attributed t o t he f act t hat dol phin work. Dr B rain D. S mith, D irector, population becomes i ncreased within Asian Freshwater an d C oastal the route of Protected Area (PA) after Cetacean Programme, i s m ost appre- it was e stablished in 2005 be tween ciated f or h is ex cellent g uideline Mingun a nd K yaukmyaung a long given on t he study. S incere gratitude Ayeyawady River. 87 Volume 2, Number 2, July-December 2014 is owed t o the m embers of W CS, i n Indonesia. WCS Working particular, U T han M yint, C ountry Paper No. 31.115 pp. Coordinator, WCS (Myanmar Programme) Dhandapani, P., 1995. Mammalia: for t heir f unding c ontributions i n river dolphin. In: Wetland conducting the research. Ecosystem Series 1: Fauna of Dolar, M.L.L., Perrin,W., Gaudiano, J.P., Yaptinchay, A.A.S.P. BIBLIOGRAPHY and Tan, J.M.L., 2002. Dolphin - Dolphin behavior. Aung Myo Chit, 2008. Current status Available from: http://www. of Irrawaddy dolphin Orcaella dolphinbehavior.org. brevirostris in the fresh water (Accessed 9 March 2010) system of Myanmar. In: T. Jefferson, A., B, D, Smith Unpublished report. 6pp. (eds). Facultative freshwater Baird, I.G. and Mounsouphom, B., cetaceans of Asia: Their 1994. Irrawaddy Dolphin ecology and conservation. pp Orcaella brevirostris in 67-74. The Raffles Bulletin of Baird, I.G. and Mounsouphom, B., Zoology. Supplement No. 10. 1997. Distribution, mortality, International Whaling Commission, diet and conservation of IWC., 2001. Report of the Irrawaddy dolphins (Oracella Standing Sub-committee on brevirostris) in Lao PDR. IUCN. (2004). IUCN Red List of Asian Marine Biology, 14: Threatened Species, Gland, 41-48. Switzerland Encyclopedia II – Beasley, I., Arnold, P. and Heinsohn, Kreb, D., 2002. Density and G., 2002. Geographical abundance of the Irrawaddy variation in skull morphology dolphin, Orcella brevirostris, of the Irrawaddy dolphin, in the Mahakam River of East Orcaella brevirostris (Owen in Kalimantan, Indonesia: a Gray, 1866). Raffles Bull. comparison of survey Beasley, I.L., Chooruk, S. and techniques. Piwpong, N., 2002. The status Mya Than Tun and Aung Myo Chit, of the Irrawaddy dolphin, 2010. Range-wide survey of Cetaceans in Asia. The Raffles Irrawaddy dolphins. WCS Bulletin of Zoology Interim Reports. 5pp. (Supplement), 10: 173 – 187. Orcaella brevirostris in Songkhla Ckilka Lake. pp. 611-613. Zoological Lake, Southern Thailand. The survey of India. Raffles Bulletin of Zoology D.B. and Syahrani., 2007. Review of Supplement, (10): 75-83. the status and conservation of Preliminary report on a small freshwater population of estuarine population of Irrawaddy Dolphins in Irrawaddy dolphins (Orcella 88 Volume 2, Number 2, July-December 2014

brevirostris) in the and conservation of Philippines. The Raffles freshwater population of Bulletin of Zoology, Irrawaddy dolphins in Supplement No.10: 155-160. Myanmar. WCS working Raffles Bulletin of Zoology paper No. 31. 115pp. Supplement, 10: 85-95 Smith, B.D., Ahmed, B., Mansur, R., Reeves, R.R., Smith, B.D., Crespo, Myan Than Tun and Thida E.A. and di Sciara, G.N., Tun, 2005. New information 2003. Dolphins, Whales and on the status of finless Porpoises. 2002– 2010 porpoise Neophocaena Conservation Action Plan for phocaenoides and Irrawaddy the World's Cetaceans. dolphins Orcaella brevirostris IUCN/SSC Cetacean in Bangladesh and Myanmar. Specialist Group. Switzerland. 19pp. 139pp Smith, B.D., Beasley, I.L. and Kreb, Small Cetaceans. Journal of Cetacean D., 2003. Marked declines in research and management populations of Irrawaddy (Supplement), 3: 263 – 291. dolphins. Oryx, 37: 401-406. Smith, B. D., Braulik, G., Strindberg, Southern Lao PDR and Northeastern S., Ahmed, B. and Munsur, Cambodia, Rep. Int. Whal. R., 2006. Abundance of Commn., 42:159-175. Irrawaddy dolphins (Orcaella Stacey, P.J. and Hvenegaard, G.T., brevisrostris) and Ganges 2002. Habitat use and River dolphins (Platanista behavior of Irrawaddy gangetica gangetica) Dolphins, Oracella estimated using concurrent brevirostris in the Mekong counts made by independent River of Laos. Aquatic teams in waterways of the Mammal, 9: 1-13. Sundarbans mangrove forest Wade, P.R., 1998. Calculating limits in Bangladesh. Marine to the allowable human- Mammal Science, 22: 527- caused mortality of cetaceans 547. and pinnipeds. Marine Smith, B.D. and Hobbs, L., 2002. Mammal Science, 14: 1- 37 Status of Irrawaddy dolphins Zool, Supplement, 10: 15-34. Orcaella brevirostris in the upper reaches of the Ayeyarwady River, Myanmar. Smith, B.D. and Jefferson, T.A., 2002. Status and conservation of facultative freshwater Smith, B.D. and Mya Than Tun, 2007. Review of the status 89