Bull sharks in the harbour

The following is an article written in July 2021 by Marco Bordieri (founder of VIZ) and reviewed by Dr Amy Smoothey (Fisheries Scientist at NSW Department of Primary Industries). Updated on 31/1/24.

Since the question of the bull sharks presence in the harbour seems to be a topic of interest, I have collected the available resources for being informed to what the science says about that. Thanks to Dr. Amy Smoothey (a known presence in most of the videos below) for the support in putting this content together.

Do bull sharks live in the harbour? 

There is a consistent number of large (2-3.2m length) bull sharks swimming throughout our harbour waterways, from the entrance to the river reaches and back , but their presence is largely seasonal as the studies have revealed (see graphs below). They travel from Queensland to breed in the Sydney Harbour during Summer. Females give birth to their pups, who will spend the first years in local rivers and estuaries till they are 1-2 metres long.

Three incidents in the harbour over the last 60 years, between January and February:

But they are not the only ones, over the years 52 fatal attacks have taken place in Sydney, most of the times inside the Harbour.  Warning - gore images: here an article from the Daily Telegraph.

A possible guidance during those months: between November and June, I would not swim in the harbour outside netted enclosures, especially in Middle Harbour as well as in the harbour West of Clifton Gardens (see the hotspots in the graph below).
Popular beaches and dive sites like Manly harbourside, Clifton Gardens, Camp Cove have regular swimmers and scuba divers in summertime and the lack of interactions or underwater sightings gives some statistical confidence (at least till a first incident occurs).

Outside that season, I have been diving over 100 times in the harbour (up to Greenwich Point) and Middle Harbour (up to Bantry Bay), covering long distances with a sea scooter, from the shallows to the 48 m of Blues Point, day or night, and never came across any bull shark, nor I have ever met divers or snorkelers who have positively identified or photographed one (anytime of the year). That said, the risk is never zero, but if we are really keen to swim or dive anywhere in the harbour, at least we can help our luck by choosing the right season. 

Marco Bordieri

Findings by DPI:

By tagging and tracking bull sharks in Sydney Harbour we have found that:

Bull shark fact sheet by DPI

additional Information around sharks in the Sydney Harbour

A study on the presence of bull sharks in the harbour from which the following figures have been taken

An animation showing the movements of the bull sharks in the harbour (2013)

Summary of bull shark presence in the harbour: what we have learnt (2020) 

An 1h documentary on sharks in the harbour (2011)

Probably not the usual day for the scientists of DPI, yet 3 bull sharks tagged in one day (1/2/2021) in locations West and East of the Harbour Bridge, length between 250 and 310 cm.

The Australian Shark Incident Database by Taronga Zoo

The International Shark Attack File by the University of Florida, the only comprehensive collection of worldwide attacks

The following is a research paper published on 10/2023, not specific to Sydney Harbour and related to white sharks

During the first three days after release, the sharks moved away from the shore and stayed mostly offshore. Although sharks gradually moved closer to the shore 10 days after release, 77% of the sharks remained more than 1.9 km away from the coast and an average of 5 km away from where they were tagged. These findings demonstrate the effectiveness of SMART drumlines as a non-lethal method to mitigate bites by White Sharks. 

The following is a research paper on bull sharks published on 31/8/2023, not specific to the Sydney Harbour

"Bull Shark (Carcharhinus leucas) Occurrence along Beaches of South-Eastern Australia: Understanding Where, When and Why"

By Amy F. Smoothey,Yuri Niella,Craig Brand,Victor M. Peddemors and Paul A. Butcher

In Australia, bull sharks are one of the species implicated most regularly in shark–human interactions. The factors affecting bull shark presence in nearshore waters of New South Wales (NSW), Australia were examined to determine periods of increased overlap with beach-users and thereby potentially increased risk of shark–human interactions. We investigated the spatial ecology of 233 juvenile and large (including sub-adult and adult, >175 cm total length) bull sharks acoustically tagged and monitored over a 5.5-year period (2017–2023) along 21 coastal beaches of NSW. Our study highlights that large bull sharks were present more in waters north of 32° S with a southward distribution during summer and autumn. The occurrence of large bull sharks in nearshore waters was greatest from midday to 04:00, when water temperatures were higher than 20 °C, after >45 mm of rain and when swell heights were between 1.8 and 2.8 m. We show that current shark bite mitigation educational messaging, incorporating proximity to rivers, turbidity (rainfall) and time of day, reflect heightened periods of the occurrence of large bull sharks. We concur with the current shark smart advice that nocturnal swimming and surfing, especially in warm waters and when water visibility is poor, should be avoided for many reasons, not the least of which being the potential presence of bull sharks. However, we suggest that time of day messaging for large bull shark presence should be modified from “dawn and dusk” to instead refer to afternoon and low-light periods 

Information around sharks in NSW

A video showing the tracked movements of white, bull and tiger sharks (2021) and more info here

VIdeo showing the presence of white sharks along NSW (2021)

A NSW Government Shark Management Strategy video (2016)

Video on white shark tagging (2019)

Key Results from shark listening stations December 2016 - October 2019

White sharks - population estimates by CSIRO using close-kin mark-recapture technique: