Kikori Delta IMMA
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
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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.
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