This WAMSI 2 project complements wider research programs which aim to increase our understanding of the distribution, abundance and population connectivity of Australian snubfin (Orcaella heinsohni) and humpback (Sousa sahulenis) dolphins, including the development of new research and monitoring methods.
In this project, we:
(i) collected genetic samples from snubfin and humpback dolphins at selected locations in the Kimberley and assessed the connectivity between these and previously sampled populations elsewhere in north-western Australian waters;
(ii) collected boat-based sightings and photo-identification data to assess the relative abundance of snubfin and humpback dolphins at selected locations in the Kimberley region; and,
(iii) investigated the application of passive acoustic monitoring (PAM) as an effective technique for monitoring these species, including: characterisation of the underwater soundscape of two Kimberley locations; and, the collection of data on the acoustic repertoire and vocalisation rates of snubfin and humpback dolphins.
Our results provide managers and policy-makers with valuable data on the relative importance of several sites within the Kimberley region to snubfin and humpback dolphins, along with an improved understanding of the connectivity of populations and the appropriate geographic scales at which to manage them. We have shown that PAM provides a method of effectively detecting snubfin and humpback dolphins in high-use areas, and have increased the information base from which to further develop PAM towards more quantitative and species-specific monitoring of these dolphins.
Our collaborative approach included training and participation by Yawuru, Bardi-Jawi, Dambimangari and Balanggarra Traditional Owners, and a Marine Park Joint Management team. This has resulted in an improved understanding and capacity of relevant local land and sea managers to collect data on these poorly-understood species within remote areas, and laid the foundation for ongoing research in the Kimberley region.
*Population genetic structure*
Under this project, the collection of genetic samples was attempted at: (1) Cone Bay (Buccaneer Archipelago) in September 2014 and 2015; and, (2) in the Cambridge Gulf (north Kimberley coast) in August 2016. Participation by AMB in a weeklong Marine Park patrol aboard the PV Worndoom facilitated limited additional sampling from the Prince Regent River (central Kimberley coast) in September 20163. Limited additional genetic samples were also obtained through opportunistic collection at Yampi Sound (Buccaneer Archipelago) during a non- WAMSI collaborative survey by AMB and the Dambimangari Rangers in October 2016. We further supplemented the sample size by: (1) incorporating snubfin dolphin samples collected at Roebuck, Cygnet and Cone Bays by SJA, AMB and DT under previous projects (see Brown, Kopps, et al. 2014), including a significant proportion collected in April 2014 which had not yet been analysed; and, (3) incorporating published genotypes from humpback dolphins sampled at the North West Cape and Dampier Archipelago (Brown, Kopps, et al. 2014). The latter facilitated a preliminary investigation of the genetic connectivity of humpback dolphins between the current focal region of the Kimberley and sites further west in the Pilbara region.
Data on the relative abundance of dolphins was collected concurrent to genetic sampling at Cone Bay in September 2014, the Cambridge Gulf in August 2016, and the Prince Regent River in September 2016 (Figure 2.1). Additional opportunistic photo-identification data was collected during acoustic data collection activities at Cone Bay in September 2015
Individual dolphins were identified from photographs based on nicks and notches on the leading and trailing edges of the dorsal fin, resulting in a catalogue of individuals for each study site
*Passive Acoustic Monitoring*
PAM of snubfin and humpback dolphins was conducted at three sites within the Kimberley; Cygnet Bay during May 2014, Roebuck Bay during July and September/October 2014 and Cone Bay during September 2015. This fieldwork was a smaller component of a larger ongoing study led by JS which was funded by the Australian Marine Mammal Centre to develop PAM methodology for these species Australia-wide.