Reef sharks at much higher risk of extinction than previously thought
Overfishing is driving reef sharks toward extinction, according to a James Cook University scientist who led a major new study published today in Science.
The five main shark species that live on coral reefs — grey reef, blacktip reef, whitetip reef, nurse and Caribbean reef sharks — have been depleted globally by an average of 63 percent, 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 depletion of widespread shark species because of the very large number of reefs and countries sampled,” said Professor Colin Simpfendorfer, lead author of the study and adjunct professor of Marine and Aquaculture Science at JCU.
“This tells us the problem for reef 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 of reef shark depletion.
“While overfishing and poor governance is 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, particularly through dive tourism. An investment in reef shark conservation can therefore be good for people too.”
Sharks and rays are common in coral reef ecosystems, but reefs that are more heavily fished, tend to become stripped of sharks, leaving the ecosystem dominated by rays. This loss of sharks could have an impact on the overall health and function of the coral reef ecosystem.
JCU’s Distinguished Professor Joshua Cinner was a co-author of the study. He said the study had some good news for how effective Australia’s management of reef sharks has been.
“Only four places in our global study had better populations of reef sharks than Australia’s east coast. We can be proud of how well we’ve managed our reef sharks, but there is still room for improvement,” said Professor Cinner.
“People need healthy coral reefs,” said Mike Heithaus, co-author of the study and executive dean of the College of Arts, Sciences & Education at Florida International University. “We are seeing that when sharks disappear, that causes other changes in these ecosystems. Keeping shark populations healthy, or rebuilding them, is important for maintaining their roles for healthy reefs.”
Early results from this study were 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 world governments to make the groundbreaking decision to better regulate trade in these and 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,” Professor 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 the research.