Shark numbers crashed by 92% over past half century, report finds

Shark numbers have plummeted in Australian waters over the past few decades in a trend researchers say is playing out across the world.

Vulnerable shark species including great whites and hammerheads have seen their numbers fall in the region by over 90 per cent since records began.

The findings contradict reports of a shark resurgence, and suggest overfishing has sent these important apex predators into a worrying decline.

Researchers used information from a shark control programme based in Queensland that has been in place since the 1960s in a bid to reduce attacks.

Nearly 50,000 sharks have been caught using baited lines and nets by the initiative, which spans thousands of miles of Australian coastline.

“What we found is that large apex sharks such as hammerheads, tigers and white sharks, have declined by 74 to 92 per cent,” said Dr George Roff from the University of Queensland, who led the study.

“And the chance of zero catch – catching no sharks at any given beach per year – has increased by as much as sevenfold.”

The scientists also noted the average size of sharks such as the tiger and hammerhead varieties had also decreased over this period. They presented their results in the journal Communications Biology.

Though they said it was impossible to know what numbers had been like at earlier dates, Dr Roff noted that 19th century explorers had described Australian coastlines as being “chock-full of sharks”.

Nearly half of all shark species found worldwide, of which there are around 400, are present in Australian waters, with particular hotspots around the eastern and western coasts.

Despite reports of rising shark attacks, the scientists said that the reality was many of these fish are actually seriously endangered.

“What may appear to be increases in shark numbers is in reality a fraction of past baselines, and the long-term trend shows ongoing declines,” said Dr Roff.

“While often perceived as a danger to the public, sharks play important ecological roles in coastal ecosystems.”

The scientists concluded that anti-shark programmes such as the one that supplied their data may be preventing the recovery of vulnerable species.

Globally, increased interactions between humans and sharks have led to the perception these predatory fish are dangerous to the public, often resulting in persecution.

Other threats to their survival include commercial fishing, especially for their fins, and accidental casualties resulting from bycatch, as well as pollution and habitat destruction around coastlines.