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Journal of the Marine Biological Association of India (2010)

Opportunistic sightings of Indo-Pacific humpback dolphin, Sousa chinensisJ. Mar. Biol. Ass. India, 52 (1) : 19 - 23, January - June 2010

Introduction

The Indo - Pacific humpback dolphin, Sousachinensis is a commonly reported delphinid fromthe Arabian Gulf (Bruyns, 1960; Al Robaae, 1970,1974; Pilleri and Gihr, 1974; Leatherwood, 1986;Gallagher, 1991; Weitkowitz, 1992; Robineau andFiquet, 1994, 1996; Baldwin et al., 1999; Preen,2004; Bishop and Alsaffar, 2008). However recentlythere is very scanty or little scientifically validinformation on distribution, abundance andbehaviour of S. chinensis from Kuwait, with theexception of recent sighting records from BoubyanIsland (Bishop and Alsaffar, 2008) andundocumented sightings by divers, tourists andresearchers. The present sighting records of S.chinensis are from opportunistic surveys off Kuwaitduring the period 2006-2009. The northern Gulfwas impacted by the gulf war oil spill in 1991 andreduction in the riverine input due to water extraction(Al-Yamani et al., 2007). Although it is reportedthat there is considerable reduction in dolphinpopulations of the gulf (Preen, 2004), further studiesare necessary to understand the reasons for thisdecline (Sheppard et al., 2010). Hence informationon dolphins is important to understand their presentabundance and distribution in the gulf.

Material and Methods

During the years 2006 - 2009, opportunisticsightings of dolphins were recorded between Al

Opportunistic sightings of Indo-Pacific humpback dolphin, Sousa chinensisfrom Kuwait waters with notes on their behaviour

M. Nithyanandan

La Ala Al Kuwait Real Estate Co. K.S.C., "Sabah Al Ahmad Sea City Project Al Khiran”,Souk Al Kuwait, 6th Floor, Office # 613, P. O. Box. 22964, Kuwait -13090.E-mail: nithyanandanm@yahoo.com

Abstract

Sightings of Indo - Pacific humpback dolphin (Sousa chinensis) recorded during 2006 - 2009 fromKuwait are reported with notes on their behaviour.

Keywords: Sousa chinensis, humpback dolphin, Kuwait waters

Khiran (28° 39’ N lat., 48° 23’ E long. ) and MinAl Zour (28º 42’ N lat., 48º 24’E long.) coastalwaters in Kuwait (Fig. 1) using a 5.3 m fibreglassspeed boat fitted with Yamaha Enduro 115 HP engine.The boat was primarily engaged for monitoring waterquality parameters. The team consisted of oneobserver onboard and a photographer. As the surveyswere opportunistic, there was no planned line-transect surveys. The number of hours of observationdepended on water quality sampling requirements.Hence, sighting frequency per hour could not bedetermined. Whenever a dolphin group was sighted,the boat was allowed to drift towards the group withengine switched off. Sighting data such as date,time, GPS location, pod size, water depth, tidalinformation, sea state (Beaufort scale) and behaviourwere recorded (Table 1). Positions were recordedusing Garmin GPS (Model GPS 60). Sightings werecarried out from 300 to 500 m from shoreline at adepth of 4 to 7 m. Bathymetry data were obtainedfrom maps (MOC, 1999). Dolphins were observedwith binoculars (Olympus 10x25WP1) andphotographed with a digital camera (Nikon D3 x 24megapixel, Nikor Lens 400 mm). Sighted dolphinswere identified following Jefferson et al. (1993). Majority of the sightings was at a distance of about4 m from the boat. The length of dolphins wasestimated by visually relating to the length of theboat. Calves were identified from their size andlighter colour (Jefferson and Karczmarski, 2001).

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Animals that were half the size of the adults wereconsidered as sub adults.

Results and Discussion

Identification and group characteristics: On alloccasions only the Indo - Pacific humpback dolphin,Sousa chinensis was sighted (Fig. 2, A-E). Sightingevents occurred at almost regular intervals (every4-5 months) during the years 2006, 2008 and 2009.No sighting was recorded in 2007 although similareffort was employed.

The group size observed was 3 to 15 (mean: 7,Table 1). According to Jefferson and Karczmarski(2001), the group size of S. chinensis varies from< 10 to < 25. However group size ranging from 30-100 individuals have been recorded in the ArabianGulf and Arabian Sea (Baldwin et al., 2004). InKuwait waters group size of 30 individuals havebeen recorded from Boubyan Island (Bishop andAlsaffar, 2008). During the present sightings,

individuals of 1 to 2.8 m total length were observed.Based on the published information on length of S.chinensis (Jefferson et al., 1993; Jefferson andKarczmarski, 2001), it is probable that juveniles,sub adults and adults occurred in the groups (Fig.2, A-E). Twice an adult humpback dolphin (< 3min total length) was sighted swimming close to a calf(Fig. 2 A & B) off Min Al Zour (28º 40’ 58.5"N lat.,48º 23’ 30.5"E long. on 25 May, 2009) and southoff Khor Al Mufateh entrance (28º 39’ 00.2"N lat.,48 º 23’ 51.7"E long. on 4 July, 2009). Calvesmeasured approximately 1 to 1.5 m in total length.Baldwin et al. (2004) have also reported sightingsof adults with calves during April-May in the ArabianGulf.

Behaviour: Two humpback dolphins sighted on25 May, 2006 at 17:00 h exhibited helical swimmingbehaviour with one lying on its back with the otheron top of it showing ventral body contact. Theseindividuals continued to swim in this pattern for less

Fig. 1. Schematic map showing sighting locations of Indo-Pacific humpback dolphin, Sousa chinensis off Kuwait(2006-09)

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Journal of the Marine Biological Association of India (2010)

Opportunistic sightings of Indo-Pacific humpback dolphin, Sousa chinensis

than a minute. This behaviour was repeated twotimes at short intervals. These observations suggestmating behaviour as described for humpbackdolphins off Pakistan by Roberts et al. (1983) andin Algoa Bay, South Africa by Karczmarski et al.(1997) and Karczmarski and Cockcroft (1999). Thisbehaviour coincides with the April–May (summer)mating season of humpback dolphin observed byBaldwin et al. (2004) in Arabian waters and peaksexual behaviour exhibited during summer in AlgoaBay, South Africa (Karczmarski and Cockcroft,1999).

The dolphins observed on 4 July, 2009, nearsouth off Khor Al Mufateh, Al Khiran (28º 39’00.2"N lat. and 48º 23’ 51.7"E long.) at 8:25 h were

chasing a shoal of pelagic Gulf herring,Herklotsichthys lossei, which leapt out of water toescape attack. This behaviour is an indication ofintensive feeding activity, similar to the feedingbehaviour in the Arabian Gulf reported by Baldwin(1995). Daytime feeding behaviour of humpbackdolphin also occurs in Algoa Bay, South Africa(Karczmarski and Cockcroft, 1999). On 8 August,2009 three calves of about 1 m length were observedwith adults near Al Khiran (28º 40’ 12.7"N lat., 48º24’ 08.6"E long.) at 6:55 - 7:50 h. Calves swamclose to the water surface rolling one over the otherin a spiral motion, flapping their tail flukes and rosevertically half out of the water (Fig. 2 D). Individualslay on their back (Fig. 2 E) for circa two seconds

Table 1. Sighting details of Indo - Pacific humpback dolphin (Sousa chinensis) from Kuwait during 2006-09

Date Observation Latitude Longitude Location Group Depth Tide Beauforttime size (m) 1 scale Remarks

25-5-06 16:30 - 28º 40’ 48º 23’ Near Min 7 6 Low 0 Two dolphins exhibited17:45 58.5 ‘N 30.5‘ E Al Zour helical swimming patterns

with ventral body contact;adult and a calf observed.

14 9-06 9:45 - 28º 39’ 48º 23’ Al Khiran 3 5.3 Low 1 Sub adults and10:10 16.2‘ N 49.9‘ E adults observed.

22-7008 10:30 - 28º 41’ 48º 23’11:00 17.2‘ N 34.2‘ E Al Khiran 14 4 High 1 Sub adults and adults.

27-8-08 8:45 - 28º 42’ 48º 23’ Min Al Zour 3 6 Low 1 Adults.9:05 18.1‘ N 27.9‘ E

11-1208 7:50 - 28º 39’ 48º 23’ Al Khiran 5 4.3 High 0 Adults8:15 42.5‘ N 56.3‘ E

19-2-09 8:00 - 28º 40’ 48º 24’ Near Min Al Zour 3 7 High 1 Adults8:25 53.8‘ N 02.0‘ E

4-7-09 8:20 - 28º 39’ 48º 23’ South of Khor 10 4.7 High 2 Adult and a calf observed8:50 00.2‘ N 51.7‘ E Al Mufateh, isolated from the group;

Al Khiran Adult dolphins observedchasing a shoal of GulfHerring, Herklotsichthys lossei

5-7-09 7:45 - 28º 39’ 48º 23’ Al Khiran 3 4.3 High 2 Adults8:05 57.9‘ N 51.7‘ E

19-7-09 7:25 - 28º 39’ 48º 23’ Near Khor 4 4.3 High 2 Adults8:45 27.0‘ N 52.4‘ E Al Ama,

Al Khiran

7-8-09 8:00 - 28º 39’ 48 º 23’ Near Al Khiran 15 4 High 2 Adults and calves8:15 53.4‘ N 53.2 ‘ E

8-8-09 6:55 - 28 º 40’ 48º 24’ Near Al Khiran 10 4 High 2 Adults and calves7:50 12.7‘ N 08.6‘ E

1 Depth (m) data from bathymetric chart (MOC, 1999).

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and then resumed normal swimming. These may besocializing behaviours exhibited by the calves, whichare similar to the observations made in adults byRoberts et al. (1983).

Based on sightings of S. chinensis off BoubyanIsland in Kuwait, Bishop and Alsaffar (2008) suggestedthe presence of a resident population. The presentstudy supports this view. It is also possible that S.chinensis in the Arabian Gulf is a single population.Genetic studies by different countries in the ArabianGulf would expand our understanding on this species.A more detailed study on diurnal behaviour, populationcharacteristics and habitat patterns will help to frame

appropriate conservation measures for the Indo-Pacifichumpback dolphin. However, it appears that theimpacts of oil spill and reduced freshwater dischargeinto the northern gulf have not restricted the breedinggrounds of S. chinensis.

Acknowledgements

I thank Mr. Fawaz Khalid Al Marzouk, Chairman,La Ala Al Kuwait Real Estate Co. K. S. C Kuwaitfor providing facilities and granting permission topublish the data; Mr. Ian Williams, Project Director,“Sabah Al Ahmad Sea City Project” for hisencouragement and support; Erickson Dayrit, A. H.Kashif and Mike Pope for photographing humpbackdolphins, Dr. David A. Jones and R. P. Kumarran,for reading earlier drafts; Drs. James Bishop, GiannaMinton, T. A. Jefferson, Louisa Ponnampalam,M/s. Howard, Tim Collins and Andrew Wilson forproviding relevant literature and information. I alsoextend my thanks to Ms. A. Priya for preparing themap, Assistant Laboratory Technician, Bapu RaoSontakke for his valuable help and the boat operators,Mohammed Hassan Ali Hassan, Abelardo Talaveraand Kulwinder Singh for their able assistance.

Fig. 2. A-E. Indo-Pacific humpback dolphin, Sousachinensis sighted off Kuwait (2006-09)

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Opportunistic sightings of Indo-Pacific humpback dolphin, Sousa chinensis

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Received : 23.09.09Accepted : 24.02.10