Shark species have declined globally by an average of 63 percent

Grey reef, blacktip reef, whitetip reef, nurse and Caribbean reef sharks — five main shark species that live on coral reefs that have declined globally by an average of 63 percent.  Researchers started to understand the causes.


“Reef shark depletion is primarily caused by excessive shark fishing. To address these issues, implementing sustainable fishing practices and creating protected areas can help reduce localised reef shark declines. Potential increases in stingray populations resulting from this imbalance may also impact other reef species. Maintaining biodiversity and managing population growth through conservation efforts are crucial to avoid further disrupting ecosystems affected by reef shark depletion”, explains MARE researcher Ashlie J. McIvor, co-writer of the study in Science Widespread diversity deficits of coral reef sharks and rays.


“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,” according to 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.”


More than 150 researchers from more than 120 institutions, 22,000 hours of video footage from baited underwater video stations have been done across 391 reefs in 67 nations and territories, to get this conclusion. Another problem: rays started to dominate.


“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 through dive tourism and if fished carefully. An investment in reef shark conservation can therefore be good for people, too”.


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.


“We need to act now to stop widespread extinction of shark species in many parts of the world”, Simpfendorfer concludes.