Sydney Harbour is an iconic urban waterway and a complex marine ecosystem home to various shark species. The definitive answer to whether sharks inhabit the harbour is yes, they are present. Understanding their presence, behavior, and the actual level of risk is key to safely enjoying the waters. This guide covers the species that visit the harbour and the simple precautions water users can take.
Species Inhabiting Sydney Harbour
The Bull Shark (Carcharhinus leucas) garners the most attention and concern. This species is well-adapted to the brackish, shallow waters of the estuary, utilizing the entire harbour from the Heads to the upper reaches of the Parramatta and Lane Cove Rivers. Bull Sharks are considered the most significant threat, as nearly all recorded unprovoked attacks in the harbour have been attributed to them.
Acoustic tagging studies show large Bull Sharks, some over 3 meters long, are regular visitors. However, the harbour is also home to many less threatening species. The Wobbegong shark (Orectolobus sp.) is common, typically lying camouflaged on the seabed and posing little risk unless provoked.
The Port Jackson Shark (Heterodontus portusjacksoni) is another frequent sight. This bottom-dweller is characterized by its blunt head and small mouth, and is considered harmless to humans. While species like the Great White Shark (Carcharodon carcharias) and Tiger Shark (Galeocerdo cuvier) are occasionally sighted near the harbour entrance, the Bull Shark remains the primary species of concern in the inner waterways.
Understanding Shark Behavior and Seasonal Presence
The presence of Bull Sharks is strongly linked to the annual cycle of water temperature. They exhibit a distinct seasonal pattern, migrating south from warmer Queensland waters to New South Wales estuaries like Sydney Harbour. This migration results in a much higher presence during the austral summer and autumn, roughly from November through June.
Bull Sharks are most abundant when the water temperature rises above 20°C to 21°C. During this warm period, females use the low-salinity river mouths to give birth, with the young remaining in the upper river reaches for their first few years. Bull Sharks use deeper shipping channels during the day, moving into shallower waters, including areas near drop-offs, during the night.
Assessing Risk and Historical Encounters
Despite the regular presence of dangerous sharks, the actual risk of an encounter in Sydney Harbour is extremely low. Unprovoked attacks are rare, especially considering the millions of people who use the harbour for recreation and transport each year. Historical data from the Australian Shark Attack File notes 43 incidents recorded between 1852 and 2014.
The last recorded fatal shark attack in Sydney Harbour occurred in 1963. Since then, there have been long periods without serious incidents, though a few non-fatal encounters were recorded in recent decades (e.g., 2009 and 2024). The infrequency of these events, despite the high seasonal presence of Bull Sharks, suggests that human-shark interactions are incidental.
Safety Measures for Harbour Users
Minimizing the already low risk involves following simple safety guidelines, especially during the warmer months when Bull Shark activity peaks.
Key Precautions
- Avoid entering the water at dawn, dusk, and at night, as sharks are more active in shallower feeding areas during these times.
- It is advisable to stick to designated swimming areas, such as netted enclosures and harbour pools, where possible.
- Stay out of the water after heavy rain or when the water is murky, as limited visibility can lead to accidental encounters.
- Avoid areas with signs of fish feeding activity, such as diving seabirds or large schools of baitfish, as sharks may be attracted to these food sources.
- Keeping informed through local warnings and the NSW SharkSmart app provides real-time information on tagged shark movements and reported sightings.