Mammals

The Australian fur seal is the predominant seal species seen in Port Phillip Bay.

The seals can be found occasionally resting on beaches around the bay, and more commonly towards the heads around the Mornington and Bellarine Peninsulas.

The bay’s Australian fur seals do not breed within the bay, but will frequently ‘haul out’ (or leave the water after foraging to spend time on land) on most man-made structures found within the bay – particularly those around Port Phillip Heads. These include Chinaman’s Hat, Pope's Eye, South Channel Fort and South Channel Marker, but also include smaller structures and buoys.

Port Phillip Bay is occasionally visited by other seal species including sub-antarctic fur seals, Australian sea lions, southern elephant seals and leopard seals. 

Litter, both general rubbish and fishing waste, are the chief threats to the seals. Curious seals can occasional swim into debris and become entangled. As the seals’ habitat is altered and degraded as a result of human activity they may start to rely on humans for food (habituation). 

By becoming used to and more familiar with humans, the seals may lose their normal ability to spot danger or hazards. This can result in the seals getting tangled in debris, injured (for example by being hit by a boat’s propeller), or may lead to conflict with humans or domestic animals.

Dogs pose a threat to seals resting on beaches. If seals are unable to escape dogs and are bitten, they are at risk of getting a transmittable disease, posing a threat to the rest of the seal population. 

Two species of dolphins can be found in Port Phillip Bay and Western Port.

Bottlenose dolphins 

The Port Phillip Bay bottlenose dolphins are smaller in size and paler in colour than their offshore counterparts. Furthermore, spots are not present on their belly, a characteristic seen in Indo-Pacific bottlenose dolphins.

Studies by the Dolphin Research Institute (DRI) indicate that 100-120 bottlenose dolphins live in the southern region of Port Phillip Bay during the warmer months.

Common dolphins

Common dolphins are visually and genetically very different from the bays’ resident bottlenose dolphins. Common dolphins can be easily recognised by the gold stripe that runs along their side. They are also smaller in size than the bottlenose.

According to the DRI, based on monitoring it has conducted in Port Phillip Bay since 2006, the community of common dolphins is small, consisting of approximately 30 dolphins residing along the eastern coast of Port Phillip Bay.

Dolphins form friendships and pair with other dolphins within the small common dolphin community.

As the dolphins’ live close to the coast they are at risk of being hit by passing boats and water craft. This may result in behaviour changes and injuries that put the community at risk.

What we need to know

There is a need to continue look at the long-term effect of vessels on the resident dolphin community to ensure they are well protected and can thrive into the future.

Find out how you can help through citizen science or learn more about threats to dolphin health in the case study.