Kikori Delta IMMA

Area Size

2 032 km2

Qualifying Species and Criteria

Australian snubfin dolphin – Orcaella heinsohni

Criterion A; B (1, 2); C (1, 2)

Australian humpback dolphin – Sousa sahulensis

Criterion A; B (1, 2); C (1, 2)

Marine Mammal Diversity 

Tursiops aduncus, Dugong dugon


The Kikori Delta IMMA is located in Gulf Province, Southern Papua New Guinea. It is recognised as one of the most important areas of forest and wetland/riverine biodiversity in the Asia/Pacific region and has been nominated as a UNESCO World Heritage Site because of its cultural and biodiversity value. The Delta is selected as an IMMA because of the consistent presence of two inshore dolphin species (Australian snubfin and Australian humpback dolphins) that occur within the delta in small resident populations. The boundary selection of the Kikori Delta IMMA is based on the core area of inshore dolphin sightings obtained during four comprehensive surveys in the region since 1999. Surveys also recorded the Indo-Pacific bottlenose dolphin and the dugong in the Delta region.

Description of Qualifying Criteria

Criterion A – Species or Population Vulnerability

Snubfin and humpback dolphins are listed as ‘Vulnerable’ on the IUCN Red List. Snubfin and humpback dolphins in the Kikori Delta are thought to be declining due to bycatch in subsistence fisheries, and possibly due to increasing levels of direct catch. There are strong indications based on interview surveys that inshore dolphin extent of occurrence in the Kikori Delta has declined. Many respondents to standardised interviews reported that prior to gillnets being introduced to the delta (approx. 1960s), inshore ‘dolphins’ (species unknown) could be sighted swimming in front of Kikori Township (approx. 50km upstream from the coastal headlands) (Beasley et al., 2011). No dolphins are now sighted in front of Kikori Township, and the maximum distance dolphins are now reported upstream is 30km from coastal headlands.

Bycatch in subsistence fisheries appears to be a problem for inshore dolphins in the Kikori Delta. Data is admittedly limited, however, it appears that mortality levels may be unsustainable. As an example, during nine days of surveys during 2015, one humpback dolphin and four snubfin dolphin carcasses were recovered that had recently (i.e. within 1-10 days) been bycaught in fishing gear (Beasley et al., 2015). One large-mesh sized gillnet set around a headland at Gaorabari Island had three snubfin dolphins caught at the same time (two adults and one calf). There were also interview reports of local fishers beginning to eat dolphin carcasses after dolphins had been accidentally bycaught in nets (Beasley et al., 2015).

Criterion B: Distribution and Abundance

Sub-criterion B1: Small and Resident Populations

Based on surveys conducted in 2013 and 2015, humpback and snubfin dolphins were found to occur in the Kikori Delta in small populations (i.e. estimated to be <100 humpback dolphins and <200 snubfin dolphins) (Beasley et al., 2013, Beasley et al., 2015). The populations of both species are assumed to be isolated and resident in the Delta based on the complete lack of species occurrence records within at least 500km from the Kikori Delta (Beasley et al., 2016).

Sub-criterion B2: Aggregations

The Kikori Delta is a large, dynamic, estuarine ecosystem, recognised as one of the most important areas of forest and wetland/riverine biodiversity in the Asia/Pacific region (WWF 2015).  Both inshore dolphin species aggregate in the outer Kikori Delta region. The core area of occurrence for both species is Banana Island/Paia Inlet east to Era/Baimurru Rivers (Bonoccorso et al., 2000; Beasley et al., 2011; 2013; 2015).

Criterion C: Key Life Cycle Activities

Sub-criterion C1: Reproductive Areas

Neonates and calves, as well as mating behaviour, have been observed for both humpback and snubfin dolphins within the IMMA (Beasley et al 2013; 2015). Therefore, the Kikori Delta region provides important habitat for reproduction of both inshore dolphin species.

Sub-criterion C2: Feeding Areas

The Kikori Delta has been identified as an important area for feeding for both inshore dolphin species. The snubfin dolphin appears to utilise specific areas within the Delta where prey aggregations occur. Humpback dolphins have often been sighted foraging in the Paia Inlet region and around the Verabari Headland/Banana Island.

Supporting Information

Asian Turtle Trade Working Group. 2000. Carettochelys insculpta. (errata version published in 2016) The IUCN Red List of Threatened Species 2000: e.T3898A97259844. Downloaded on 29 March 2017.

Beasley, I., Golding, M. and Anamiato, J. 2013. Looking for Pidu (Dolphins and Dugongs) in the Kikori Delta of Papua New Guinea – 2013 Surveys. Unpublished report submitted to James Cook University.

Beasley, I., Golding, M. and Anamiato, J. 2015. Looking for Pidu (Dolphins and Dugongs) in the Kikori Delta of Papua New Guinea – 2015 Surveys. Unpublished report to James Cook University.

Beasley, I., Golding, M. and Gebia, O. 2011. Surveys for inshore dolphins in the Kikori Delta, Papua New Guinea. Unpublished report to the Australian Marine Mammal Centre.

Beasley, I., Jedensjo, M. and Anamiato, J. in review, Confirmed Occurrence of the Australian snubfin dolphin, Orcaella heinsohni in Papua New Guinea: Conservation Considerations for Small Isolated Populations. Ecology and Evolution.

Beasley, I., Jedensjo, M., Wijaya, G. M., Anamiato, J., Kahn, B. and Kreb, D. 2016. Observations on Australian Humpback Dolphins (Sousa sahulensis) in Waters of the Pacific Islands and New Guinea. Advances in marine biology, 73, 219-271.

Beasley, I., Robertson, K. M. and Arnold, P. 2005. Description of a new dolphin, the Australian snubfin dolphin Orcaella heinsohni sp. n.(Cetacea, Delphinidae). Marine Mammal Science, 21, 365-400.

Bonoccorso, F., Leary, T. and Anamiato, J. 2000. A small survey for marine mammals in the Kikori Delta region of PNG.: Unpublished report to WWF-PNG and the National Museum and Art Gallery of Papua New Guinea.

Brown, A. M., Bejder, L., Pollock, K. H. and Allen, S. J. 2016. Site-specific assessments of the abundance of three inshore dolphin species to inform conservation and management. Frontiers in Marine Science, 3, 4.

Cagnazzi, D., Parra, G. J., Westley, S. and Harrison, P. L. 2013. At the heart of the industrial boom: Australian snubfin dolphins in the Capricorn Coast, Queensland, need urgent conservation action. PloS One, 8, e56729.

Compagno, L., Pogonoski, J. and Pollard, D. 2009. Glyphis glyphis. The IUCN Red List of Threatened Species 2009: e.T39379A10221801. Downloaded on 29 March 2017.

Department of Environment 2013. Coordinated research framework to assess the national conservation status of Australian snubfin dolphins (Orcaella heinsohni) and other tropical inshore dolphins. Unpublished Report.

Hettler, J., Irion, G. and Lehmann, B. 1997. Environmental impact of mining waste disposal on a tropical lowland river system: a case study on the Ok Tedi Mine, Papua New Guinea. Mineralium Deposita, 32, 280-291.

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.

Kyne, P., Carlson, J. and Smith, K. 2013. Pristis pristis. The IUCN Red List of Threatened Species 2013: e.T18584848A18620395. Downloaded on 29 March 2017.

Lanfredi, C. and Kaschner, K. 2017. Global reference points and niche model baseline indicators of AOIs. Unpublished report submitted to the IMMA Regional Workshop, Apia, Samoa 27-31 March 2017.

Liem, D. S. 1983. Survey and management of wildlife resources along the Purari River. The Purari—tropical environment of a high rainfall river basin. Springer.

Miller, C. 2007. Current State of Knowledge of Cetacean Threats. Diversity and Habitats in the Pacific.

Parra, G., Schick, R. and Corkeron, P. 2006a. Spatial distribution and environmental correlates of Australian snubfin and Indo‐Pacific humpback dolphins. Ecography, 29, 396-406.

Parra, G. J. 2006. Resource partitioning in sympatric delphinids: space use and habitat preferences of Australian snubfin and Indo‐Pacific humpback dolphins. Journal of Animal Ecology, 75, 862-874.

Parra, G. J., Corkeron, P. J. and Marsh, H. 2006b. Population sizes, site fidelity and residence patterns of Australian snubfin and Indo-Pacific humpback dolphins: Implications for conservation. Biological Conservation, 129, 167-180.

Petr, T. 2012. The Purari—tropical environment of a high rainfall river basin: Tropical Environment of a High Rainfall River Basin, Springer Science and Business Media.

Reeves, R. R. 1999. Marine mammals in the area served by the South Pacific Regional Environment Programme (SPREP), South Pacific Regional Environment Programme.
WWF 2015. Kikori River Basin Conservation Blueprint. WWF – Papua New Guinea Programme.


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