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Dolphin distribution

As part of our partnership with the WA Marine Science Institution (WAMSI), researchers have mapped the distribution of bottlenose dolphins.

31 January 2024

Westport has partnered with the Western Australian Marine Science Institution (WAMSI) to deliver the $13.5 million WAMSI-Westport Marine Science ProgramA report form Project 8.1 Dolphin distribution is now available on WAMSI's website. Below, the Westport team has provided a summary of this report and its key findings.

Indo-Pacific bottlenose dolphins are well-loved locals and a protected species.

These dolphins live in communities, with separate groups identified in Cockburn Sound, Owen Anchorage, and the Swan River. However, they face many threats from habitat loss, entanglement with fishing, and high mortality rates.

This study was commissioned to develop a better understanding of the current number and distribution of the dolphins in Cockburn Sound and Owen Anchorage, as well as their patterns of movement as they forage across the seasons.

Data taken from boats between 2011 and 2015 was used as the baseline for the modelling, with 72 studies undertaken in Cockburn Sound and 73 in Owen Anchorage during that period.

This historical data will be supplemented and validated by current surveys to monitor the populations and their movement over the course of a year.

This research will help us understand potential impacts of the port development on the local dolphin community and improve the scientific knowledge available around dolphin habitat and distribution.

“The Indo-Pacific bottlenose dolphins are an important and highly visible feature of the Cockburn Sound and Owen Anchorage ecosystem” said Westport’s Environmental Impact Assessment Manager.

“Westport is committed to preserving the long-term health of Cockburn Sound and habitat supporting the dolphin population.”

What the report found:

  • It’s estimated there are 65 dolphins in Cockburn Sound, 45 in Owen Anchorage, and 16 in the Swan Canning Riverpark.
  • Owen Anchorage dolphins stay relatively close to the shoreline and boat ramps, with seasonal shifts in response to surface sea temperature and water visibility.
  • Cockburn Sound dolphins seek shallower waters across a range of locations in the Sound, including the northern and southern tip of Garden Island, and Kwinana Shelf.
  • Seagrass beds were key foraging grounds for the Cockburn Sound dolphins.
  • Owen Anchorage has experienced high usage and long-term dredging, which suggests that dolphins in this region have become accustomed to vessel traffic and industrial operations. This is the same for the dolphins in the Fremantle Inner Harbour.
  • The accumulation of multiple activities and increased shipping could trigger behavioural responses, which requires ongoing research and monitoring.

The review recommended further research and dedicated studies be conducted in both Owen Anchorage and Cockburn Sound, closer to, during, and after the development of Westport.

Work currently underway will enable a fuller understanding of the dolphin population and potential effects of environmental changes on the behaviour, health, and population dynamics of dolphins that use these areas. Project findings will be utilised by Westport to ensure future mitigation activities are designed and implemented with the greatest chance of success.

You can read the full report here.

Read the full update here:

  • Westport Navigate Newsletter January 2024

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