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Overfishing erased sharks from many of the world's reefs, researchers say

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A global survey of reef sharks, like these shown here, found they are functionally extinct on nearly 20% of the world's reefs, but healthy populations still exist where protective laws are enforced. Photo courtesy of Global FinPrint
A global survey of reef sharks, like these shown here, found they are functionally extinct on nearly 20% of the world's reefs, but healthy populations still exist where protective laws are enforced. Photo courtesy of Global FinPrint

Aug. 27 (UPI) -- Teams of researchers around the world recently confirmed what many of them suspected -- that overfishing wiped out sharks on up to 20% of the world's reefs.

A study by the Global FinPrint initiative also confirmed that affluent nations with strict fishing controls, especially the United States and Australia, still have an abundant number of sharks.

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The global survey of 371 reefs in 58 countries provides a benchmark for future shark studies and clear evidence for supporting conservation, its authors said.

"It was kind of surprising how widespread the depletion of sharks was," said Demian Chapman, associate professor of biological sciences at Florida International University in Miami.

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"The Coral Triangle region around Indonesia would have been teeming with sharks long ago, but we barely found any there," he said.

Starting in 2015, Chapman and other scientists used baited remote video systems to record sharks, rays and other sea life on 371 reefs in 58 countries. Full results of the study were published in July in the journal Nature, titled Global Status and Conservation Potential of Reef Sharks.

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The lack of sharks on one-fifth of the reefs hadn't been documented previously, Chapman said.

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"The good news is you don't need a total ban on shark fishing. You can manage it," he said. "We do shark fishing in Florida, but we do it very carefully. There's a limit to ensure that sharks can repopulate."

His team surveyed reefs from Miami to the lower end of the Florida Keys.

"We found sharks nearly everywhere. It wasn't as good as the Bahamas, where all shark fishing was banned in 2011," Chapman said. "But Florida is a particularly useful example of good shark management because we found reefs with many sharks near big population centers and development."

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He said the Bahamas also banned destructive fishing gear, known as longlines and gillnets, nearly 30 years ago because diving and seeing sharks is a big driver of tourism.

Nations in which sharks were virtually absent included the Dominican Republic, the French West Indies, Kenya, Vietnam, the Windward Dutch Antilles and Qatar. Only three sharks were observed during more than 800 survey hours in those regions, according to the study.

The data can guide meaningful, long-term conservation plans for protecting reef sharks, according to the Paul G. Allen Family Foundation, a philanthropic organization founded by the late Microsoft co-founder.

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"We knew sharks were disappearing in alarming numbers, and there was a really severe lack of data," said Rebecca Ng, senior program officer for oceans at Vulcan Inc., a Seattle area company that manages the Allen foundation's philanthropic efforts.

"Having strong fisheries management measures is going to be really important," Ng said.

The survey by Global FinPrint underscores the importance of shark nurseries in the United States and other nations with protected shark populations, said Stephen Kajiura, professor of biological sciences at Florida Atlantic University's College of Science in Boca Raton.

"A lot of these sharks are highly migratory species, and the problem is we might enact protections in the U.S. but that only works while they're here," Kajiura said. "So it's important to have these protections become global as possible."

He said species that benefited from regulations in the United States include sandbar and blacktip sharks.

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