Two-thirds of sharks and ray in coral reefs facing extinction: SFU study

January 19, 2023
Photo courtesy of Colin Simpfendorfer

Nearly two-thirds of all shark and ray species that live among coral reefs are threatened with extinction, according to a new study from Simon Fraser University researchers.

They found sharks and rays are the most threatened groups found in coral reefs.

The study, published this week in Nature Communications, found that 59 per cent of the 134 coral-reef associated shark and ray species are threatened with extinction – mainly due to overfishing, but compounded by climate change and habitat loss.

“It was a bit surprising just how high the threat level is for these species,” says Samantha Sherman, a post-doctoral research fellow at SFU, and lead author of the study. “Many species that we thought of as common are declining at alarming rates and becoming more difficult to find in some places.”

Coral reefs are amongst the most diverse ecosystems one earth, harbouring more than one-third of the ocean’s fish species. Yet, they face some of the most intense and widespread threats of any ecosystem, such as climate change, poor water quality and coastal development.

But overfishing remains the most immediate direct and indirect threat to most reefs, according to the study’s authors.

Until now, researchers suspected that the most commonly observed reef shark populations have been in decline based on a global video survey of that found that some sharks were functionally extinct at 20 per cent of the sites.

However, these surveys counted only the most common 11 shark species, offering little insight into how the other 123 species were doing.

The team recently completed International Union for Conservation of Nature (IUCN) Red List assessments and were able to pin-down the state of many more species and provide a comprehensive picture of the threats facing them.

Of the 134 species assessed, 59 per cent are in one of the three threatened categories (Vulnerable, Endangered and Critically Endangered). A further 13 per cent of species are Near Threatened.

Fishing was identified as the main culprit, mainly due to intentional and unintentional catch in both small and large-scale fisheries.

Coastal reef fisheries directly support the livelihoods and food security of over half a billion people, but the study says this human footprint far exceeds the productivity of many of the world’s reef sharks and rays.

To stop the decline of sharks and rays, the authors say science-based fisheries management with strong enforcement is needed, along with well-implemented marine protected areas.

They also encourage neighbouring countries to implement regional level management to protect migratory and transient species.

“Protective measures for sharks have only begun to show up recently. As these species have late maturity and long lives, the effects of these protections may not be seen for decades,” says SFU professor Nick Dulvy, Canada Research Chair in Marine Biodiversity and Conservation. “This is why we need to implement management immediately to conserve these species and secure a future for coral reefs.”