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Overfishing is driving reef sharks toward extinction, according to new study published this week in Science. The five main shark species that live on coral reefs — grey reef, blacktip reef, whitetip reef, nurse and Caribbean reef sharks — have declined globally by an average of 63 per cent, according to the scientists of Global FinPrint, a five-year international study supported by the Paul G. Allen Family Foundation.

“These are some of the best estimates of population decline of widespread shark species because of the very large number of reefs and countries sampled,” says Colin Simpfendorfer, lead author of the study and adjunct professor of Marine and Aquaculture Science at James Cook University in Australia. “This tells us the problem for sharks on coral reefs is far worse and more widespread than anyone thought.”

Results from this latest research, which includes 22,000 hours of video footage from baited underwater video stations across 391 reefs in 67 nations and territories, indicates widespread overfishing is the main culprit driving reef sharks toward extinction. Sharks and rays are common in coral reef ecosystems, but as reefs are more heavily fished, they have become stripped of both shark and ray species or stripped of just shark species, leaving the ecosystem dominated by rays.

"What we found is a predictable pattern of loss that comes from overfishing, where catches of sharks lead to changes in how the world’s coral reefs are functioning,” says Aaron MacNeil, quantitative lead scientist for Global FinPrint and a professor in Biology at Dalhousie University’s Ocean Frontier Institute. “Ultimately this leads to losses in reef health that degrade their ability to provide the kinds of goods and services that people depend on. It’s shockingly widespread.”  

“While overfishing and poor governance are associated with the absence of these species, they are still common in Marine Protected Areas (MPAs) and places where shark fishing was banned or highly regulated,” said Demian Chapman, lead scientist of Global FinPrint and director of the Sharks and Rays Conservation Program at Mote Marine Laboratory. “Reef sharks can be important for human livelihoods through dive tourism and if fished carefully. An investment in reef shark conservation can therefore be good for people too”.

Early results from this study were previously used to update the status of four of these species to more threatened categories on the International Union for the Conservation of Natures (IUCN) Red List. They were also presented during the most recent Conference of the Parties of the Convention on the International Trade in Endangered Species of Wild Fauna and Flora (CITES), helping governments make the groundbreaking decision to better regulate trade in more than 50 additional species of sharks. 

“This means no trade should come from nations where the take of the species will threaten its survival,” Dr. Simpfendorfer said. “This study can be used to help identify those nations where such catches would be detrimental. We need to act now to stop widespread extinction of shark species in many parts of the world.”

More than 150 researchers from more than 120 institutions across the world contributed to this research.

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Media contact: 

Alison Auld 
Senior Research Reporter 
Communications, Marketing and Creative Services 
Dalhousie University 
Cell: 1-902-220-0491 
Email: alison.auld@dal.ca