Westport has partnered with the Western Australian Marine Science Institution (WAMSI) to deliver the $13.5 million WAMSI-Westport Marine Science Program. This 3-year program is developing the latest data, information and modelling on the complex environmental systems and community values associated with Cockburn Sound.
Project 8.3: Trophic ecology of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in Owen Anchorage and Cockburn Sound inferred by stable isotopes.
Research Theme: Apex Predators and Iconic Species
Researchers: D Chabanne, Harry Butler Institute, Murdoch University
Publication Date: September 2024
Research to understand the preferred diet and prey of the bottlenose dolphin in Cockburn Sound.
The Indo-Pacific bottlenose dolphin is a welcome fixture in Cockburn Sound and Owen Anchorage.
While the mammals are regularly spotted in Cockburn Sound and Owen Anchorage, dolphins are rarely observed eating prey. This has meant there has been a gap in knowledge of the diets of dolphins. By understanding the diet of dolphins, the impact of human activities on either a food source or a foraging zone can be better assessed, helping to inform better decisions that protect the dolphin habitat.
In this research program, a total of 49 biopsy skin samples from adult and juvenile dolphins were taken from dolphins across a 180 Km2 radius, from Rockingham to Fremantle, through different seasons of the year.
The samples were used to analyse stable isotopes in the skin. The metabolic processes within an organism drive isotopic composition, which can be measured using an isotope-ratio mass spectrometer. Carbon ratios play a crucial role in pinpointing sources of primary production and offering a snapshot of the individuals recent foraging habits.
What the report found
- There was a distinct seasonal pattern to feeding habits, with dolphins feeding on sea mullet in summer, and focusing on cuttlefish, squid and octopus during winter.
- Different sub-groups were identified within the dolphin community, with different feeding habits.
- Female dolphins demonstrated higher site-fidelity, meaning they would return to the same feeding location and had specialised foraging techniques.
How Westport will use the report
This study has given Westport a stronger insight into the foraging habits for dolphins in Cockburn Sound, and the seasonal variations in their diet. It’s provided critical insights that can be considered in environmental management activities for the development of the port, and ongoing conservation efforts.
Read the full report here.
