Cams reveal shark numbers in decline
HALIFAX: An unprecedented global survey has revealed a shocking decline in the number of reef sharks, with the predators “functionally extinct” on nearly 20% 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% of the reefs we surveyed didn’t have any sharks 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,” Prof MacNeil, an associate professor at Dalhousie University, said.
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 criticised 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 information about shark populations in coastal areas.