Kuching Bay IMMA

Size in Square Kilometres

475 km2

Qualifying Species and Criteria

Irrawaddy dolphin – Orcaella brevirostris

Criterion A; B (1)

Finless porpoise – Neophocaena phocaenoides

Criterion A; B (1)

Humpback dolphin – Sousa chinensis

Criterion A; B (1)

Marine Mammal Diversity 

Neophocaena phocaenoides, Orcaella brevirostris, Sousa chinensis, Tursiops aduncus

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Kuching Bay in Sarawak, East Malaysia, encompasses two large estuaries and interconnecting river systems feeding into the area. Kuching Bay provides habitat for four species of cetaceans with overlapping distributions: Irrawaddy dolphins, Indo-Pacific finless porpoises, Indo-Pacific humpback dolphins, and Indo-Pacific bottlenose dolphins. Line transect and mark recapture studies indicate population sizes of approximately 200 Irrawaddy dolphins, 150 finless porpoises, and 100 humpback dolphins. Photo-identification studies demonstrate that Irrawaddy dolphins and humpback dolphins are resident in the area and observations of calves and feeding indicate that the area is important for these species’ year-round reproduction and feeding. Kuching Bay supports local artisanal fishing, with a high degree of overlap between fishing effort and dolphin distribution, creating a risk of bycatch. Freshwater inputs from flood mitigation channels, extensive aquaculture, and coastal development also present threats to the cetaceans. However, coastal marine protected areas in the heart of the area provide potential mechanisms for conservation and mitigation measures.

Description of Qualifying Criteria

Criterion A – Species or Population Vulnerability

Irrawaddy dolphins are considered Endangered on the IUCN Red List of Threatened Species (Minton et al. 2017), and the Kuching Bay population may comprise one of the few remaining healthy populations of over 100 individuals. Studies demonstrate that the species is resident year round, feeding and breeding in the study area, and demonstrate a high degree of site fidelity with a dependence on nearshore or estuarine waters (Minton et al. 2011, Minton et al. 2013, Peter et al. 2016b). The population is known to be at risk of entanglement in fishing gear (Peter et al. 2016a), and studies indicate that this population is afflicted by skin nodules that may be an indication of environmental degradation and/or decreased immunity (Van Bressem et al., 2014).

Finless porpoises and humpback dolphins are listed as Vulnerable on the IUCN Red List of Threatened Species (Jefferson et al. 2017; Wang and Reeves 2017) and have been recorded in four incidents of bycatch in the Kuching bay, involving crab traps as well as gillnet fisheries (Sarawak Dolphin Project, unpublished data). One of the bycaught finless porpoises was a calf whose teeth had not erupted indicating a very young individual (Sarawak Dolphin Project, unpublished data).

Criterion B: Distribution and Abundance

Sub-criterion B1: Small and Resident Populations

Surveys conducted between 2008 and 2013 yielded higher encounter rates with Irrawaddy dolphins in the nearshore waters of Kuching Bay than waters further offshore, or the neighboring Muara Tebas Bay to the east (Minton et al. 2011; 2013).  This, coupled with the high rate of re-sights of individually identified Irrawaddy dolphins (Minton et al. 2013), and small core ranges (Zulkifli Poh, 2013), provides strong evidence that the Irrawaddy dolphin population numbering fewer than 300 individuals is resident and confined to the area. In addition several observations of calves of all three cetacean species have been recorded in the area (Minton et al. 2011), including Irrawaddy dolphin and finless porpoise calves with fetal folds (Sarawak Dolphin Project, unpublished data). Third-party reports and photographs shared by experienced wildlife guides have confirmed the occurrence of mating  bottlenose dolphins and the birth of a humpback dolphin in Kuching Bay.

Supporting Information

Beasley, I. and Jefferson, T.A. 1997. Marine mammals of Borneo: A preliminary checklist. The Sarawak Museum Journal, 51:193–216.

Jefferson, T.A. and Rosenbaum, H.C. 2014. Taxonomic revision of the humpback dolphins (Sousa spp.), and description of a new species from Australia. Marine Mammal Science, 30:1494–1541.

Jefferson, T., Smith, B.D., Braulik, G. and Perrin, W. 2017. Sousa chinensis. The IUCN Red List of Threatened Species. e.T82031633A82031644. [online] Available at

Minton, G., Peter, C. and Tuen, A.A. 2011. Distribution of small cetaceans in the nearshore waters of Sarawak. Raffles Bulletin of Zoology, 59:91–100

Minton, G., Peter, C., Zulkifli Poh, A.N., Ngeian, J., Braulik, G., Hammond, P.S. and Tuen, A.A. 2013. Population Estimates and Distribution Patterns of Irrawaddy Dolpihns (Orcaella brevirostris) and Indo-Pacific Finless Porpoises (Neophocaena phocaenoides) in the Kuching Bay, Sarawak. Raffles Bulletin of Zoology, 6:877-888

Minton, G., Zulkifli Poh, A.N., Peter, C., Porter, L. and Kreb, D. 2016. Indo-Pacific Humpback Dolphins in Borneo: A Review of Current Knowledge with Emphasis on Sarawak. In: T.A. Jefferson and B.E. Curry (eds) Advances in Marine Biology, Volume 73, pp. 141-156. Oxford: Academic Press.

Minton, A.G., Smith, B.D., Braulik, G., Kreb, D., Sutaria, D. and Reeves, R. 2017. ‘Orcaella brevirostris. The IUCN Red List of Threatened Species 2017. e.T15419A50367860’. [online]. Available at: https://www.iucnredlist.org/species/15419/123790805

Peter, C. 2012. ‘Distribution pattern, habitat characteristics and population estimates of Irrawaddy dolphins (Orcaella brevirostris) in Kuching Bay, Sarawak’. MSc thesis. Sarawak: Universiti Malaysia Sarawak

Peter, C., Ngeian, J., Minton, G., Zulkifli Poh, A.N., Grinang, J. and Tuen, A.A. 2016a. ‘Artisanal fisheries and cetaceans in Kuching Bay, Sarawak, East Malaysia: Threats and potential mitigation’, paper delivered at the meeting of the Scientific Committee of the International Whaling Commission SC/66b/SM09:18

Peter, C., Zulkifli Poh, A.N., Ngeian, J., Tuen, A.A. and Minton, G. 2016b. ‘Identifying Habitat Characteristics and Critical Areas for Irrawaddy Dolphin, Orcaella brevirostris: Implications for Conservation’. In: I Das, A.A. Tuen (eds.) Naturalists, Explorers and Field Scientists in South-East Asia and Australasia, pp 225-238. Switzerland: Springer.

Van Bressems, M.F., Minton, G., Sutaria, D., Kelkar, N., Peter, C., Zulkarnaen, M., Mansur, R.M., Porter, L., Rodriquez Vargas, L. H. and Rajamani, L. 2014. ‘Cutaneous nodules in Irrawaddy dolphins: An emerging diseases in vulnerable populations’. Diseases of Aquatic Organisms, 107: 181–189 [online]

Wang, D. and Reeves, R. 2017 ‘Neophocaena phocaenoides. The IUCN Red List of Threatened Species 2017. eT198920A50386795’ [online] Available at

Zulkifli Poh, A.N. 2013. ‘Habitat characteristic and overlap of small cetaceans in Kuching Bay, Sarawak, Malaysia’. MSc thesis. Sarawak: Universiti Malaysia Sarawak.

Zulkifli Poh, A.N., Peter, C., Ngeian, J., Tuen, A.A. and Minton, G. 2016. ‘Abundance Estimates of Indo-Pacific Humpback Dolphins (Sousa chinensis) in Kuching Bay, East Malaysia’. Aquatic Mammals 42:462-465


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