Are reef sharks going extinct?

Now, Colin Simpfendorfer at James Cook University in Queensland, Australia, and an international team of 150 scientists have conducted the largest global survey of sharks and rays living on coral reefs ever undertaken. Their results show that reef shark species are at a far higher risk of extinction than previously thought and that five of these species meet the criteria for the IUCN’s Red List endangered category. Sharks are being replaced by rays at many locations, fundamentally altering reef ecosystems and further fuelling declines in reef diversity.  

“We sampled almost 400 coral reefs in 67 nations and territories to understand the effects that humans have had on over 100 shark and ray species,” says Simpfendorfer. “Overfishing is driving resident reef sharks towards extinction. We highlight global declines between 60% and 73% for the five most common reef shark species. Individual shark species were not found at between 34% and 47% of the reefs that we surveyed.” 

“Reef sharks are indicative of healthy reef systems,” says Michael Berumen at KAUST, in Saudi Arabia, who also worked on the project. “When sharks decline, the whole reef ecosystem begins to falter.”

To conduct the survey, the team used more than 22,000 baited remote underwater video stations. They monitored the richness of different species present and the composition of elasmobranch assemblages frequenting each location. There were pronounced differences between assemblages around wealthier nations where governance is often stronger and marine areas are highly protected, and those regions that are poorer with a lack of shark protection measures in place. 

The study included data from several Middle Eastern countries: Qatar, the UAE, and Saudi Arabia. Elasmobranch populations in the region have been badly affected by fishing, particularly in the Arabian Gulf, although some parts of the Red Sea are faring better. 

“Urgent government action is needed to address these shark declines,” says Simpfendorfer. “Coral reefs can support sustainable livelihoods for millions of people if they are managed effectively, with protection against overfishing in place.”

Severe population declines in one location did not mean that the same species had declined as dramatically elsewhere, notes Simpfendorfer. This suggests that direct intervention in the form of effective species-specific management and enforced marine protected areas will reverse these trends. 

“In the Saudi Arabian Red Sea, the ongoing Giga-Project investments indicate a renewed interest and priority to protect reefs, which are among Saudi Arabia’s most valuable natural treasures,” says Berumen.

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