Dolphins under threat

An Irrawaddy dolphin
An Irrawaddy dolphin (Orcaella brevirostris). (Photo: Isabel Beasley)
Dr Isabel Beasley and Olo Gebia (WWF Melanesia Program) discuss dolphin sightings with villagers who live near the Omati River in the Kikori Delta.Dr Isabel Beasley conducts a small meeting at Veribari village in the Kikori Delta, to introduce the upcoming dolphin project and describe the dolphin species that occur in the delta.A map of Dr Isabel Beasley's study sites in the Kikori River Delta and the Gulf of Carpentaria.

The Kikori River Delta of Papua New Guinea is thought to be home to a number of threatened cetacean species, including the Indo-Pacific humpback dolphin (Sousa chinensis) and Irrawaddy dolphin (Orcaella brevirostris). Only one small study has previously been conducted on marine mammals in the delta, so virtually no information is available about these, or other species, in the region.

Dr Isabel Beasley of James Cook University says it’s important to establish the status of inshore dolphins in the Kikori River Delta for conservation and management purposes.

‘We still don’t know which species of Orcaella occurs in Papua New Guinea,’ she says.

‘Although Irrawaddy dolphins have been recorded in the delta, they could actually be the newly described Australian snubfin dolphin’.

Dr Beasley was instrumental in the discovery of the Australian snubfin (Orcaella heinsohni) in 2005. On the IUCN Red List, the Australian snubfin is listed as ‘Near Threatened’, and the Irrawaddy as ‘Vulnerable’, as a result of both species’ limited range, low densities in surveyed areas, and continuing vulnerability to human impacts such as overfishing, habitat loss and bycatch.

Snubfin dolphins are particularly vulnerable to local extinction because they are currently considered endemic to northern Australian waters. They occur in small, genetically isolated sub-populations and inhabit coastal/estuarine waters that are subject to wide-spread habitat degradation and development.

‘More extensive surveys are needed in northern Australia and Papua New Guinea to support a reassessment of the Australian snubfin dolphin under international and national legislation,’ Dr Beasley says.

Through the Indo-Pacific Cetacean Research and Conservation Fund (IPCF), Dr Beasley, in collaboration with Dr Eric Verheij and Mr Olo Gebia of the World Wildlife Fund Western Melanesia Program, will collect baseline information on the diversity, distribution and abundance of dolphins and other marine mammals in the Kikori River Delta, while increasing the local research capacity of communities, and local and national governments.

To do this the team will:

  • conduct a local community workshop to inform Kikori residents of the project and acquire local knowledge of marine mammals;
  • conduct a training course for local and provincial government scientists and community conservation workers on marine mammal research methods;
  • conduct transect surveys in the delta to determine the distribution, abundance and species of marine mammals; and
  • produce a management plan for marine mammals in the region in collaboration with the local community and Department of Environment and Conservation.

Dr Beasley says the research and subsequent management plan will identify key species and their habitat and improve understanding of the threats to marine mammals in the delta. A better knowledge of critical habitats will help to mitigate the effect of coastal development on marine mammal populations.

The work will also contribute significant information towards a nomination to the Australian Government to have the Australian snubfin dolphin listed as ‘Threatened Fauna’ under the Environmental Protection and Biodiversity Conservation Act (EPBC Act).

Bridging the gulf for dolphin conservation

In a related project funded by the Bill-Dawbin Post-doctoral Fellowship, Dr Beasley will spend the next three years studying the Australian snubfin dolphin and Indo-Pacific humpback dolphin in the Gulf of Carpentaria in northern Australia. Both dolphin species occur in small, localised populations in northern Australia but their status in the Gulf remains unknown. While anecdotal evidence suggests that some parts of the Gulf may be important for these species, a recent survey around the Sir Edward Pellew Island Group in the southwestern Gulf sighted only a few individuals.

 ‘The Australian snubfin dolphin is currently recognised as Australia’s only endemic cetacean and it is likely that Australian populations of the humpback dolphin will also be recognised as separate from the Indo-Pacific species,’ Dr Beasley says.

‘While we suspect these dolphins are endangered or vulnerable, we do not have enough information on their distribution and abundance to list them as such under Australian Commonwealth or state legislation, to ensure effective management of populations and their habitat.’

To help fill this knowledge gap Dr Beasley will collate information on the biology and occurrence of both species in the Gulf of Carpentaria. This information will feed into models to identify potentially important coastal dolphin habitat in the Gulf. Dr Beasley will then select areas in which to conduct boat-based surveys for the dolphins, in collaboration with Indigenous Sea Ranger groups and Traditional Owners.

‘Effective management of Australian snubfin and humpback dolphin populations, and associated species and habitat, needs to be a high priority for Australia, to ensure the long-term viability of these species. This project will provide important data to assist this process,’ Dr Beasley says.

WENDY PYPER

Corporate Communications, Australian Antarctic Division