Dampier Archipelago IMMA

Criterion A – Species or Population Vulnerability

The dugong (Dugong dugon) and Australian humpback dolphin (Sousa sahulensis) are both listed as Vulnerable on the IUCN Red List of threatened species. In addition, though not as threatened globally, the Near Threatened Indo-Pacific bottlenose dolphin (Tursiops aduncus) are all known to reside in the IMMA as well.

Criterion B: Distribution and Abundance

Sub-criterion B1: Small and Resident Populations 

Small resident pops of Indo-pacific bottlenose and Australian humpback dolphins and dugongs have all been recorded for the IMMA. Research by the Western Australian state government has been underway since 2015 investigating the population of coastal dolphins that inhabit this area using aerial surveys across the Pilbara region and more focussed boat-based surveys in Dampier Archipelago.  Three aerial surveys were conducted between 2015 and 2017 and 5 vessel-based surveys between 2014 and 2019 (Waples and Raudino, 2019).  Both species of dolphins have been recorded during each survey, with some individuals re-sighted over five years, indicating there may be a degree of site fidelity to the area.  Foraging behaviour and the presence of calves have been observed indicating the area contains both foraging and breeding habitat. Results from these surveys are being analysed and abundance estimates will be published soon.  Initial results indicate estimates for humpback and bottlenose dolphins are in the low thousands  for both species across the Pilbara.  As an example, boat-based surveys conducted in May 2019 encountered 25 groups of dolphins during the 7 days of field work, including 76 Indo-Pacific bottlenose dolphins and 36 Australian humpback dolphins. Many of the dolphin groups also contained young calves.

Sub-criterion B2: Aggregations

The IMMA is on the migration route for the breeding stock D humpback whale population.  Dampier Archipelago in particular is recognised as a resting/staging area for adult females and calves during the southern migration (Jenner et al 2001).  Female humpback whales occasionally give birth in the waters of the Dampier Archipelago, although the main calving area is further north. Adult humpback whales and their young also aggregate in the Archipelago on their southern migrations in early spring, and Mermaid Sound is a significant staging/resting area (Jenner et al 2001) and Nickol Bay is emerging as an important resting area with numbers ranging from a maximum of 188 sightings in August to a minimum of 15 sightings in November 2009  (Cummins 2010).

Criterion C: Key Life Cycle Activities

Sub-criterion C1: Reproductive Areas

Vessel based surveys have been conducted across the Dampier Archipelago IMMA since 2015 and have recorded the presence of humpback dolphin calves, including neonates. Humpback whale mothers and calves are reported to rest in the area on their southbound migration (Jenner et al 2001; Cummins 2010).

Sub-criterion C2: Feeding Areas

Dugongs have been recorded in the IMMA, though little is known of their abundance, density or distribution to date. Dugongs are thought to be resident in coastal waters of the Pilbara coast and are sighted year-round, having a strong association with seagrass habitat. A recent study by Cleguer et al., 2021 found dugong abundance ranged from 47 individuals in June (CV = 0.17) to 103 individuals in May (CV = 0.36). Aerial surveys have confirmed the presence of dugongs in the IMMA, with herds in the shallow waters of Dampier, Cape Preston and Regnard islands (Waples and Raudino 2019).

Criterion D: Special Attributes

Sub-criterion D1: Distinctiveness

Humpback dolphin males display a multi-modal sexual behaviour whereby they present marine sponges to mature female humpback dolphins (Allen et al., 2017). This behaviour has only been observed in northern Australia at a few key sites, other than Dampier, including Coral Bay, North West Cape, Cygnet Bay, Cone Bay (Allen et al., 2017) and in Queensland (Parra, 2007). The use of sponges in this context is very different to the use of sponges for foraging in Shark Bay by Indo-Pacific bottlenose dolphins. Indeed, the only other marine mammal known to carry objects (plant matter, stones and clay) in the context of socio-sexual display is Amazon river dolphins (Inia geoffrensis) (Martin et al., 2008).