Shark expert explains how injuries can reveal secrets of shark attacks

While South East Queensland beaches are protected by nets and drum lines to try and stop dangerous sharks, waters north of Cairns operate under completely different rules.

A young boy is fighting for his life after surviving a shark attack on Thursday Island, but the tragic event has raised question surrounding shark management in the top end. Picture: Supplied.

Aggressive and dangerous sharks are dealt with differently north of Cairns compared to South East Queensland because of one key factor, a marine expert says.

Samuel Nai, 14, remains in a critical condition at Townsville Hospital after suffering a catastrophic shark bite while fishing on Saturday afternoon.

Across Queensland, baited drum lines are deployed along the coast to catch and either kill or tag sharks deemed a dangerous species.

Samuel Nai was attacked by a shark at Thursday Island on Saturday, October 11. Picture: Supplied

But above Cairns this program ceases entirely.

When asked by the Cairns Post whose responsibility it was to mitigate shark risks, Queensland’s Department of Primary Industries said the Australian Fisheries Management Authority controlled Torres Strait waters while AFMA said local and state governments were responsible.

Under the Queensland Shark Control Program baited drum lines and shark nets are deployed across the state to protect swimmers. Picture: Jeff Krause

Reef Ecologic chief executive Dr Adam Smith said regardless of who was responsible the level of risk was fundamentally different to other parts of the state.

“It’s all about beaches,” he said.

“A lot of people don’t swim at the Torres Strait … they might dive while catching a cray or spearfishing or jump in to cool off but they aren’t sitting in the water like surfers might be.

“Risk is always about a number of factors and one of them is about people and time spent in the water.”

Since 1855, there have been more than 60 shark attacks across the Torres Strait with all but four put down to tiger sharks.

Dr Smith said the child's injuries would give scientists the most important clue in determining what species it was.

“Often when a person is bitten the shark will actually leave a tooth which can be used with the size and shape to determine what type of shark was responsible,” he said.

“A tiger shark for example, will leave a particular sawing bite mark because they have a triangular sawing tooth.

“But I think many of them could be put down to misidentification, anything big or a man-eater could have been labelled a Tiger.”

“Anecdotally I think there are more bull sharks, or they are learning, depredation is much more common with bull sharks.”

The attack occurred near Cook Esplanade, Thursday Island in shallow water. Picture: Google Maps

The devastating attack occurred just after 6pm and in shallow water.

Dr Smith said sharks will enter these habitats at dawn and dusk searching for food.

“Earlier and later in the day they will come in much shallower looking for food,” he said.

“You’re more likely to encounter sharks at dawn and dusk and I certainly believe that there's a bit of a season you see them become more active … in November and December.”

Originally published as Shark expert explains how injuries can reveal secrets of shark attacks