Shark numbers along the Queensland coast have declined by more than 90 percent for some species in the past five decades, according to new research that calls for better protection for threatened species in Australian waters.
Australia has 170 types of sharks out of about 440 species globally. Great white and grey nurse sharks are listed as threatened in Australian waters.
Researchers from the University of Queensland and Griffith University have analyzed data from shark control programs to gauge changes in populations over the past five decades. Nets and baited hooks have been used in Queensland to reduce the risk of attacks on swimmers and surfers.
The research teams looked at the number of white, tiger, hammerhead and whaler sharks caught from the early 1960s to 2016.
Fewer sharks, smaller sharks
What they found was a shock, according to George Roff from the University of Queensland, who was one of the authors of the study.
'The results are quite striking," he said. "What we found over the last 50 years is a dramatic decline in the numbers of apex sharks on the Queensland coastline. So the number of wild sharks on our beaches have declined by between 74 and 92 percent.
"(At) the same time, the size of the sharks are also getting smaller, so there are fewer and smaller sharks on Queensland beaches than there were 50 years ago, and this includes the globally endangered hammerhead sharks that have declined by 92 percent and importantly white sharks that are listed as vulnerable in Australia (and) have shown no sign of recovery despite protections that have been put in place over two decades ago to stop fishing,' he added.
Researchers are blaming overfishing for a sharp fall in hammerhead and great white shark populations. They say that the apparent collapse of certain shark species would indicate that the overall health of the oceans is also in decline. They say there should be greater protection for some of nature's greatest scavengers and predators.
Scientists insist that factors such as climate change, which is affecting shark numbers, could not explain the scale of the decline.
Australian states have tried different ways to reduce the risk of shark attacks. Authorities in New South Wales favor a high-tech approach to deter and detect predators, including drones that use artificial intelligence to spot sharks near surfers.
In January 2014, the Western Australian government responded to a series of attacks with a controversial catch-and-kill policy. Almost 70 sharks were caught and shot before the strategy was abandoned after a recommendation by environmental officials.