The number of reef sharks has declined dangerously, mainly because of fishing, with a "worrying" number of species in functional extinction, revealed Wednesday an unprecedented study. For four years, 15,000 remote-controlled underwater cameras filmed more than 370 coral reefs from nearly 60 countries to identify the world's shark population.
The results are "very worrying," warned Aaron Macneil, co-author of the study published in the British scientific journal Nature . "We expect… that there are sharks on all the coral reefs in the world and it is very worrying to discover that there are none in 20% of the reefs we have monitored", said he insisted at a press conference.
Destructive fishing techniques
No sharks have been detected in coral reefs in eight countries, including Qatar, India, Vietnam and Kenya. These results do not mean that there are no sharks in the waters of these countries, but that their numbers in the coral reefs are dangerously low. “These countries are places where we say that reef sharks (…) play no role in the ecosystem and that they are in functional extinction,” continued the associate professor at Dalhousie University in Canada.
The study, which draws on more than 15,000 hours of recording, points to destructive fishing practices - such as the use of gillnets and longlines - as the main culprits for the decline in shark populations. Both methods are criticized for their high levels of bycatch, indiscriminately capturing marine organisms including endangered species.
We need a protection policy
The authors also warn that policies focused on protecting reef sharks may not be enough, given that predators depend on healthy and abundant coral reefs to survive. Modeling suggests that "just focusing on reef sharks can only restore about 35%" of sharks, said Aaron MacNeil.
"These kinds of results show that the conservation of any group of animals must be part of a larger ecosystem," he continued. Banning destructive fishing practices, imposing catch limits, closing fishing grounds and creating shark sanctuaries could help restore shark populations, the authors said. "There are places where reef sharks are doing well, where they could repopulate and rebuild in these degraded areas," insisted Mike Heithaus, study co-author and lecturer at Florida International University.
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