Dr. Delphine Chabanne, a Murdoch University researcher, has conducted over a decade of study on Perth's two dolphin populations in the Swan-Canning Rivers and Cockburn Sound, focusing on their welfare and ecology. She also gave a presentation to students on Perth’s coastal dolphins in late 2025 as part of WAMSI's Thinking Blue program.
Dolphin Species and Population
In Perth, the only dolphin species present is the Indo-Pacific bottlenose dolphin. Approximately 120 dolphins inhabit Cockburn Sound and Owen Anchorage, while about 25 utilize the Swan Canning estuary. Observations indicate that dolphins occasionally move between these communities, with instances of mating. For example, a dolphin named ‘Hugs,’ born in Owen Anchorage, has since spent most of her time in the lower Swan Canning estuary after having her first calf in 2021.
Research Methodology
Dolphin surveys typically involve travelling by boat in specific patterns (parallel lines or zig-zag) to locate groups. When dolphins are spotted, researchers take photographs of their dorsal fins, which are unique due to nicks, scars, and notches acquired over time, allowing for individual identification and tracking. Data on group composition, behavior, and environmental conditions like water temperature and depth are also recorded. A 'Finbook' is issued on the River Guardians website to help identify local dolphins. Dolphins generally demonstrate resilience to shark bites, particularly if injuries avoid vital organs in their softer ventral areas.
Seasonal Diet
Perth’s dolphins display an opportunistic feeding strategy, adapting their diet seasonally. In summer, they tend to consume more benthic detritivore fish, such as mullet. During winter, their preference shifts to cuttlefish and octopus, which dolphins may toss into the air to break into smaller pieces before swallowing.
Threats to Dolphins
Significant threats to dolphin populations include entanglement in fishing lines and nets, with dolphin calves being especially vulnerable due to their smaller size and thinner blubber. Boat strikes pose another danger. Underwater noise pollution can disturb their behavior, as dolphins rely on sound for navigation and communication. Maintaining clean waterways, free of pollution, is also critical for their overall health. Cetacean Morbillivirus, which weakens the immune system, has been linked to dolphin deaths in Perth, contributing to fatalities in 2009 and 2019.
Key Dolphin Characteristics
- Female dolphins can live for approximately 40 years, while males typically live around 35 years.
- They use echolocation, emitting clicking sounds and interpreting the returning echoes to understand their surroundings and locate food.
- Dolphin pregnancies last 12 months, and calves remain with their mothers for 3 to 5 years, learning essential survival skills.
- Dolphins rest one half of their brain at a time, enabling them to remain alert for predators or danger and to surface for air.
Dolphin Protection Recommendations
Recommendations for protecting dolphins include maintaining clean oceans, estuaries, and coastlines, participating in beach clean-ups to prevent rubbish entry into water, carefully disposing of fishing lines and other gear, reducing boat speeds, refraining from feeding dolphins, and joining citizen science programs.