Shark populations decline by up to 90 percent along Australian coast

December 14, 2018, 12:08 p.m.
Great white shark (Carcharodon carcharias) swims in greenish water
Photo: Longjourneys/Shutterstock

Things aren't looking great for multiple shark species that call Australia's East Coast home.

According to a study published in Communications Biology, great white, hammerhead, tiger and whaler sharks along the Queensland coast have all suffered significant population declines over the past 55 years. Great whites and hammerheads have seen their populations fall by 92 percent; the whaler shark population dipped by 82 percent; and tiger sharks numbers have dropped by 74 percent.

University of Queensland and Griffith University researchers analyzed shark control data collected between 1962 and 2015. The shark control program uses mesh nets and baited drumlines "with an aim to 'minimize the threat of shark attack on humans' by reducing the local populations of large sharks to minimize the probability of encounters between sharks and swimmers," the researchers explain in their paper.

Researchers weighed multiple factors as potentially doing the most harm to shark populations, including the placement of nets and materials used to make them, whether or not the historical numbers were ultimately reliable, and if the sharks were simply learning to avoid the program's measures and climate change.

Ultimately, those factors — and even climate change — couldn't account for the steep declines. Researchers determined that the biggest driver was commercial overfishing of the sharks, suggesting that "sharks may be susceptible to even relatively low levels of fishing pressure."

Researchers suggest that shark-controlling efforts be redirected to protecting the sharks. As apex predators, declines in the shark population could have wide-reaching effects on multiple ecosystems and food webs in the region.

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