When bull sharks are most active: Huge mistake in Australian shark protocol

A group of Australian researchers say they’ve discovered when the biggest bull sharks are most active, and it’s not when most people think.

Currently, official Australian advice recommends that water-goers avoid swimming and surfing at dawn, dusk and night, saying these are times when “sharks can see you but you can’t see them”.

The advice also recommends staying away from “murky, dirty water”, water that is contaminated by sewage or waste and water used by fishermen.

However, a new study indicates that advice mightn’t be so helpful.

The researchers, from the NSW Department of Primary Industries (DPI) and Macquarie University, tracked the movements of bull sharks off the NSW coast and discovered when the largest members of the species are most active.

The study involved 233 tagged bull sharks, which were tracked along 21 coastal NSW beaches between 2017 and 2023.

The researchers found the presence of large bull sharks was greatest from midday through to 4am. They found an increased possibility of the sharks being near to shore between 6pm and 1am.

The scientists also revealed certain conditions that increased one’s chances of encountering a large bull shark. These included when the water temperature was higher than 20C, after heavy rain or when the water was murky.

“These conditions are favourable for ambush predators like bull sharks,” Amy Smoothey, scientific officer and shark biologist at NSW DPI, told LiveScience.

“Be aware during periods of lowlight levels, as these are times when bull sharks are typically more active and you may not be able to see the approaching shark.”

Now, the researchers are calling for official advice to be changed to reflect their findings, recommending that swimmers and surfers avoid the water during the afternoon and in lowlight conditions as well.

Bull sharks are one of the three shark species — along with great whites and tiger sharks — that are involved in the vast majority of fatal attacks in Australian waters.

Bull sharks, which can grow to 3.5 metres long, are often considered particularly dangerous because they love warm, coastal waters and can travel up freshwater rivers.

The most recent fatal attack by a bull shark in Australia occurred in February this year, when 16-year-old Stella Berry was killed in a river in Perth.

However, the researchers also highlighted that unprovoked shark bites are relatively rare.

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