A global survey has revealed a shocking decline in the number of reef sharks, with the predators ‘functionally extinct’ on nearly 20 percent of places studied.
The four-year study used more than 15,000 baited remote underwater video cameras, so-called “chum cams”, to see 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 expected 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 is very concerning,” he said during 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.
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 lives of reef sharks.
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.
The new study relied on more than 15,000 hours of video from the underwater cameras, analyzed by a team of volunteers and researchers.
Banning harmful fishing practices, imposing catch limits, closing areas to fishing and creating shark sanctuaries could all help restore shark populations, the authors said.
But they emphasized the need for solutions that fit particular circumstances, for example where fishing communities rely on shark fishing to survive.
The study also warns that policies focused on protecting reef sharks may not be enough, given the predators rely on a healthy reef and a lot of prey to survive.
“Results like these demonstrate that conservation of any group of animals must be embedded within a wider ecosystem,” MacNeil told AFP.