A recent record of the Indo-Pacific Humpback Dolphin Sousa chinensis (Osbeck, 1765), (Mammalia: Cetartiodactyla: Delphinidae) from the western shores of Kachchh, Gujarat, India

The Indo-Pacific Humpback Dolphin Sousa chinensis (Osbeck, 1765), is widely distributed in the shallow coastal and inshore waters of the eastern and western Indian ocean and northwestern, southwestern, and western central Pacific oceans (Reeves et al. 2008). Indo-Pacific Humpback Dolphins have been recorded all along the Indian coast by (Blandford 1888–91; Lydekker 1903, 1908; Mohan 1982, 1983; Krishnapillai & Kasinathan 1988; Parsons 1998; Kumarran 2002; Sutaria & Jefferson 2004; Afzal et al. 2008; Muralidharan 2013). S. chinensisis comes under ‘Near Threatened’ (NT) category on the IUCN Red List (Reeves et al. 2008) but it is included in Appendix I of the Conservation of International Trade of Endangered Species of Flora and Fauna (CITES) and listed in Appendix II of the Convention on Migratory Species (CMS). So far, studies on cetaceans in India were limited to age determination (Mohan 1995), stomach contents (Leatherwood & Reeves 1989), molecular identification (Jayashankar et al. 2008) and behaviour (Bijukumar & Smrithy 2012; Muralidharan 2013). However, detailed studies on the behaviour and ecology of S. chinensis have not been adequately covered throughout its range and therefore only limited knowledge is available about the ethology of this species inhabiting the western coasts of India.

Indo-Pacific Humpback Dolphins occur in near shore shallow waters, generally at 20m depth, often near estuaries (Ross et al. 1994). Water depth is probably the main factor limiting their offshore distribution, and the 25m isobath has been suggested to represent the critical depth in the South African region (Karczmarski et al. 2000). These dolphins have also been reported to occur in a variety of coastal habitats including sandy beaches, enclosed bays and coastal lagoons, mangrove channels, over sea grass meadows, around rocky and coral reefs, and in turbid estuarine waters (Beadon 1991; Durham 1994; Jefferson 2000; Karczmarski 2000; Karczmarski et al. 2000).

Gujarat has a coastline of 1650km (21.9% of the Indian coastline), which is the longest among all the maritime states of India. The Gujarat coastline has two gulfs, namely, the Gulf of Kachchh and Gulf of Khambhat, and it comprises a variety of habitats such as mangroves, coral reefs, mudflats, sands/beaches, salt marshes, rocky area, salt pans and other vegetated areas and it provides a suitable niche for a variety of marine animals including marine mammals. The Zoological Survey of India has reported three species of dolphins such as the Spinner Dolphin, the Long-Beaked Common Dolphin, Striped Dolphin, and the Indo-Pacific Hump-backed Dolphin from Gujarat (Kumarran 2012). Joglekar et al. 1977 reported some stranded dolphins from Devka and Udwada, southern Gujarat based on skeletal evidence, but their identification was not confirmed. Sutaria & Jefferson (2004) recorded 21 groups of S. chinensis that consisted of 78 individuals from the southern Gulf of Kachchh. These individuals were largely found at a depth of from 1–10 m and the average group size remained between 1.5 and 3.0 individuals.

Jakhau port (23014’27.96”N & 68036’26.27”E) is an important seasonal fishing centre in the Kachchh District of Gujarat. A total of six individuals of S. chinensis was observed near the Jakhau creek, which is the western part of the Gulf of Kachchh (Image 1). The GPS location of the sighting was 23014’28.5”N & 68035’54.0”E. The dolphins were spotted at mid-high tide on 03 December 2014 at 09.53hr (IST). These dolphins were found less than 10m away from the shore at a depth of 1–10 m. The dolphins were observed for a time period of 20 minutes. The dolphins while leaping continuously, kept following the boat for sometime and approached as close as 5m during certain occasions (Images 2–4). These dolphins were also observed at the same time at the same location the following day. A questionnaire survey of nearby fishermen had confirmed that these dolphins were seen in this part of Gujarat during winter. Therefore, it is assumed that weather condition and prey availability is favorable for this species during this period. This is the first record of S. chinensis in the western shore of Kachchh District; a detailed study regarding the distribution of this species is required across the creek system of Western Kachchh.

References

Afsal, V.V., K.S.S.M. Yousuf, B. Anoop, A.K. Anoop, P. Kannan, M. Rajagopalan & E. Vivekanandan (2008). A note on cetacean distribution in the Indian EEZ and contiguous seas during. Journal of Cetacean Research Management 10(3): 209–16.

Beadon, J.J. (1991). A note on cetaceans seen and live-captured in the Gulf of Aquaba and the Gulf of Suez, 15 September 1980 through 1 September 1981. UNEP Marine Mammals Technical Report 3: 111–114.

Bijukumar, A. & R. Smrithy (2012). Behaviour of Indo-Pacific Humpback Dolphin, Sousa chinensis (Osbeck) in the Ashtamudi estuary, southwest coast of India. Journal of the Marine Biological Association of India 54(2): 34.

Blanford, W.T. (1888). The Fauna of British India including Ceylon and Burma. Taylor and Francis, London,

Durham, B. (1994). The distribution and abundance of the Humpback Dolphin (Sousa chinensis) along the Natal coast, South Africa. Diss. Thesis, University of Natal.

Jayashankar, P., B. Anoop, E. Vivekanandan, M. Rajagopalan, K.M.M. Yousuf, P. Reynold, P.K. Krishnakumar, P.L. Kumaran, V.V. Afsal & A.A. Krishnan (2008). Molecular identification of delphinids and finless porpoise (Cetacea) from the Arabian Sea and Bay of Bengal. Zootaxa 1853: 57–67.

Jefferson, T.A. (2000). Population biology of the Indo-Pacific Hump-backed Dolphin in Hong Kong waters. Wildlife monographs 144: 1–65.

Joglekar, N.J., S.B. Vasavada & R.M. Desai (1977). On the stranding of Sotalia (Cetacea: Odontoceti) off the coast of Daman (South Gujarat, India). Journal of the Marine Biological Association of India 17: 695­–696.

Karczmarski, L. (2000). Conservation and management of Humpback Dolphins: the South African perspective. Oryx 34(3): 207–216.

Karczmarski, L., M. Thornton & V.G. Cockcroft (2000). Daylight occurrence of Humpback Dolphins Sousa chinensis in Algoa Bay, South Africa. African Journal of Ecology 38: 86–90.

Kumaran, P.L. (2002). Marine mammal research in India: A review and critique of methods. Current Science 83: 1210–1220.

Kumarran, R.P. (2012). Cetaceans and cetacean research in India. Journal of Cetacean Research Management 12(2): 159–172.

Leatherwood, S. & R.R. Reeves (1989). Marine mammal research and conservation in Sri Lanka, 1985–1986. UNEP.

Lydekker, R. (1903). On two dolphins from Madras. Journal of the Bombay Natural History Society 15: 408–414.

Lydekker, R. (1908). On an Indian dolphin and porpoise. Proceedings of the Zoological Society of London 1908: 802–808.

Mohan, R.S.L. (1982). A note on the fetuses of the dolphin Tursiops truncatus and Sousa plumbea from the Southwest coast of India. Indian Journal of Fisheries 29: 249–252.

Mohan, R.S.L. (1983). On a Humpback Dolphin Sousa chinensis in captivity. Indian Journal of Fisheries 29: 160–161.

Mohan, R.S.L. (1995). Age determination of dolphins entangled in gill nets along the Kerala coast. Journal of the Bombay Natural History Society 92: 77–80

Muralidharan, R. (2013). Sightings and behavioral observations of Indo-Pacific Humpback Dolphins Sousa chinensis (Osbeck, 1765) along Chennai coast, Bay of Bengal. Journal of Threatened Taxa 5(15): 5002–5006; http://dx.doi.org/10.11609/JoTT.o3454.5002-6

Parsons, E.C.M. (1998). Observations of Indo-Pacific Humpbacked Dolphins, Sousa chinensis, from Goa, Western India. Marine Mammal Science 14: 166–170.

Pillai, S.K. & C. Kasinathan (1988). Report on two dolphins washed ashore near Mandapam. Marine Fisheries Information Service, Technical and Extension Series 88: 21.

Ross, G.J.B., G.E. Heinsohn & V.G. Cockcroft (1994). Humpback Dolphins Sousa chinensis (Osbeck, 1765), Sousa plumbea (G. Cuvier, 1829) and Sousa teuszii (Kukenthal, 1892). Handbook of Marine Mammals 5: 23–42.

Singh, H.S. (2003). Marine protected areas in India. Indian Journal of Marine Sciences 32(3): 226–233.

Sutaria, D. & T.A. Jefferson (2004). Records of Indo-Pacific Humpback Dolphins (Sousa chinensis Osbeck, 1765) along the coasts of India and Sri Lanka: An overview. Aquatic mammals 30(1): 125–136.