Reef tales: candid cams reveal shark populations in decline

July 26 ------ An unprecedented global survey has revealed a shocking decline in the number of reef sharks, with the predators “functionally extinct” on nearly 20 percent of sites studied. The four-year study used more than 15,000 baited and remotely operated cameras — so-called “chum cams” — to obtain the first comprehensive picture of where reef sharks are thriving and where they are virtually non-existent.

The results, from over 370 reefs in nearly 60 countries, are alarming, said lead author Aaron MacNeil. “We expect… that there should be sharks on every reef in the world and to find 20 percent of the reefs we surveyed didn’t have any sharks on is very concerning,” he told a press briefing. At reefs surveyed in eight countries, including Qatar, India, Vietnam and Kenya, no sharks were detected at all.

The findings do not mean sharks do not exist in the waters of these countries, but are evidence that their numbers on reefs are now critically low. “These nations are places where we’re saying that reef sharks… play no role in the ecosystem there and they’re functionally extinct,” MacNeil, an associate professor at Dalhousie University said.

– ‘Transformational’ –

The study, published Wednesday in the journal Nature, says destructive fishing practices are the most likely culprit for the losses. “The use of gillnets and longlines had the strongest negative influence on the relative abundance of reef sharks,” the study says. Gillnets use a wall of netting, while longline fishing involves a single line strung with multiple baited hooks. Both methods have been criticized for high levels of bycatch — snaring marine life indiscriminately, including endangered animals.

The study backed by the Global FinPrint project was motivated by the dearth of big-picture information about shark populations in areas near coastlines. In the past, researchers relied either on examining catch records, or underwater visual surveys by divers, both of which have shortcomings and produce results that are difficult to compare, MacNeil told AFP. The new study relied on more than 15,000 hours of video from the underwater cams, analyzed by a team of volunteers and researchers. That method has given the team “a baseline against which we can both predict and gauge the success of future conservation actions for reef sharks,” he added.

“It is transformational.”

And while the results might appear disheartening, the researchers said there are were some bright spots.

Source: mb.com.ph