Kaimana, West Papua IMMA

Criterion A – Species or Population Vulnerability

The Australian humpback dolphin and dugong are listed as ‘Vulnerable’ by the IUCN, and considered to be declining throughout their range (Parra et al. 2017; Marsh and Sobtzick, 2015). The major threats are known to be habitat loss and degradation, by-catch in fisheries, water pollution, underwater noise, floods and cumulative threats (Parra et al. 2017). West Papua represents the northwest extent of Australian humpback dolphins’ known distribution, with the species confirmed to occur in three locations in West Papua: Mayalibit Bay, Bintuni Bay and Kaimana Region. These regions comprise extensive mangrove, estuarine and coastal habitat particularly important for their survival. Arguni Bay within the Kaimana Region is notably important, as it consists of extensive riverine/estuarine/coastal habitats. These habitats are subsequently important for the survival of Australian humpback dolphins and dugong in the region.

Criterion B: Distribution and Abundance

Sub-criterion B2: Aggregations

There are no known population or residency estimates for Australian humpback dolphins in the Kaimana Region. However, based on other known populations in northern Australia and southern Papua New Guinea, it is likely that the Australian humpback dolphin population in Arguni Bay is relatively small and resident (Parra et al. 2018, Beasley et al. 2013; 2015). Kaimana is one of only three regions in West Papua where Australian humpback dolphins have been sighted, with no other Australian humpback dolphin sightings known for the region. As a result of the habitat characteristics throughout Kaimana, it is proposed that aggregations of Australian humpback dolphins in this region represent an important concentration for this species. Kahn (2009) considered the population of Bryde’s whales in Triton Bay to be small and resident. Although there was limited justification for this statement based on nine survey days, there is undoubtedly an important aggregation of Bryde’s whales in the Kaimana Region, particularly between Bitsyara and Triton Bays via the Namatote Strait.

Criterion C: Key Life Cycle Activities

Sub-criterion C2: Feeding Areas

The Kaimana Region is a notably important marine mammal feeding area, as the diversity of habitats represents an important prey base to a variety of marine mammal species. These habitats include riverine/coastal/estuarine mangroves regions of Arguni Bay, coral islands, and oceanic deep narrow passages and canyons. As a result of this rich biodiversity and productivity, the region provides an important nutritional base on which many marine mammal species depend. The known habitat preferences of humpback dolphins are shallow and protected coastal habitats such as inlets, estuaries, shallow bays, inshore reefs and coastal archipelagos rather than in open stretches of coastline. In Queensland and Northern Territory, humpback dolphins are mainly found in water less than 20 km from the nearest river mouth and in water less than 15-20 m deep (Parra et al. 2004; 2017). Few animals have been observed in waters up to 30-50 m deep, but remained in close proximity (within 5 km) to the coast (Parra et al. 2004; 2017). In both Queensland and Northern Territory humpback dolphins have been also recorded as far as 20-50 km upstream in large rivers such as the East Alligator River, Northern Territory, and in the Fitzroy and Brisbane rivers in Queensland (Cagnazzi, 2010, Palmer et al. 2014, Parra et al. 2004). In Southern Papua New Guinea, humpback dolphins were only found adjacent to delta/coastal mangroves, and no further than 2km from the coast (Beasley et al. 2013; 2015). Arguni Bay within the Kaimana Region therefore represents ideal habitat to support biological productivity and concentration of prey aggregations for inshore dolphins, such as the humpback and Indo-Pacific bottlenose dolphin.