“Sharks and rays are the canary in the coalmine of overfishing,” a scientist says.
Close on four out of 10 shark and ray species are at risk of going extinct due to overfishing, habitat loss, climate change and water pollution.
This stark assessment has come courtesy of scientists who have recently examined the conservation status worldwide of nearly 1,200 species of chondrichthyes, which comprise sharks, rays, and chimeras.
During the first such global assessment in 2014, it was found that nearly a quarter (24%) of chondrichthye species were threatened. By now, however, as many as 37.5% of chondrichthyans are throught to be facing extinction in the world’s oceans, partly as a result of improved data on their populations.
An estimated 41% of 611 rays species studied are at risk, as are 36% of 536 sharks species with an additional 9% of 52 chimaera species, the scientists have found.
“Overfishing is the universal threat affecting all 391 threatened species and is the sole threat for 67.3% of species and interacts with three other threats for the remaining third: loss and degradation of habitat (31.2% of threatened species), climate change (10.2%), and pollution (6.9%). Species are disproportionately threatened in tropical and subtropical coastal waters,” the scientists explain in a study.
And it isn’t just numerous species of chondrichthyans that are critically endangered. Countless marine species, large and small, are at risk of going extinct in coming years and decades, according to the International Union for Conservation of Nature (IUCN).
In fact, the planet’s oceans are facing a “global extinction crisis,” scientists say.
“Sharks and rays are the canary in the coalmine of overfishing,” observes Nicholas Dulvy, a professor at the Simon Fraser University in Canada who was the study’s lead author.
“If I tell you that three-quarters of tropical and subtropical coastal species are threatened, just imagine a David Attenborough series with 75% of its predators gone. If sharks are declining, there’s a serious problem with fishing,” Dulvy explains.
“Our study reveals an increasingly grim reality, with these species now making up one of the most threatened vertebrate lineages, second only to the amphibians in the risks they face,” the scientist elucidates.
“The widespread depletion of these fishes, particularly sharks and rays, jeopardises the health of entire ocean ecosystems and food security for many nations around the globe,” he adds.
These findings will come as no surprise to people familar with the massive devastation inflicted worldwide on sharks caught for their fins for use in shark-fin soup, a delicacy in Chinese cuisine. Countless sharks and rays are also caught as bycatch, especially in the tropics where they used to be abundant.
“The tropics host incredible shark and ray diversity, but too many of these inherently vulnerable species have been heavily fished for more than a century by a wide range of fisheries that remain poorly managed, despite countless commitments to improve,” says Colin Simpfendorfer, an adjunct professor at James Cook University in Queensland in Australia.
“As a result, we fear we will soon confirm that one or more of these species has been driven to extinction from overfishing – a deeply troubling first for marine fishes,” he laments.
However, stepped-up protection measures and new limits imposed on unsustainable fishing pratices can turn things around. Several species of tuna, which were fished nearly into extinction a decade ago, have largely recovered as of late, according to the IUCN.
In the group’s latest listing of endangered species the Atlantic bluefin tuna has been removed from the “endangered” category and reclassified as a species of “least concern” while the Southern bluefin is now listed as “endangered” rather than “critically endangered.”
At the same time, albacore and yellowfin tunas have gone from being listed as “near threatened” to “least concern.”
“These Red List assessments are proof that sustainable fisheries approaches work, with enormous long-term benefits for livelihoods and biodiversity,” stresses Bruce B Collette, chair of the IUCN’s SSC Tuna and Billfish Specialist Group.
“We need to continue enforcing sustainable fishing quotas and cracking down on illegal fishing,” Collette says.