A quarter of sharks and rays are threatened with extinction due to overfishing, according to the first-ever global analysis of these species by the International Union for Conservation of Nature (IUCN). The most recent edition of the IUCN’s “Red List” of threatened and endangered species assessed the conservation status of 1,041 shark, ray, and chimaera species, Live Science reports.

According to the Red List, sharks, rays, and chimeras – cartilaginous fishes (Chondrichthyans) – are at higher risk of extinction than most other species on the list. Only 23 percent of shark, ray, and chimera species are categorized as being of “least concern,” or relatively unthreatened.

The cartilaginous fishes are mainly threatened by overfishing. Reported catches of sharks, rays, and chimeras peaked in 2003, although researchers say catches are likely greatly under-reported. Many catches are unintentional, although there are developing markets for sharks and rays that are adding stress to the species, according to IUCN.

Intentional killing due to a perceived risk of harm the species could cause to humans or fishing equipment is contributing to the threatened status of at least 12 species. Rays are more threatened than sharks.

“Our analysis shows that sharks and their relatives are facing an alarmingly elevated risk of extinction,” Nick Dulvy, co-chair of the IUCN shark specialist group said in a press release. “In greatest peril are the largest species of rays and sharks, especially those living in shallow water that is accessible to fisheries.”

The global market for shark fins, which are used to make shark fin soup, is contributing to a decrease in shark species as well as some ray species such as the guitarfish. According to Live Science, shark-finning is a process by which as many as 70 million sharks per year are caught, have their fins cuts off, and are thrown back into the ocean to die.

IUCN researchers said the cartilaginous fishes are also hunted for their meat, which is used to create products like Chinese tonic, made from manta ray and devil ray gills, and pharmaceuticals, made from deep-sea shark livers. In 2012, The Times reported that the giant manta ray is facing a new threat from a “coastal tonic” from Southern China that has been “resurrected by shark fin traders.” Ingredients of the tonic also include endangered sea horses, pipefish, and ginseng.

The threatened status of cartilaginous fishes is exacerbated by the species’ relatively slow reproduction. “Sharks, rays and chimeras tend to grow slowly and produce few young, which leaves them particularly vulnerable to overfishing,” Sonja Fordham, deputy chair of the IUCN shark specialist group, said in a press release.

Researchers said threatened species are most prevalent in the Mediterranean Sea and in the Indo-Pacific, particularly the Gulf of Thailand. There are also many threatened shark and ray species in the Red Sea, between Africa and Asia.

Scientists are particularly concerned about rays (including sawfish, guitarfish, stingrays, and wedgefish) because the public is largely unaware of the widespread decrease of those species, while public awareness of sharks’ threatened status is growing. Five of the seven most-threatened families are rays.

“Significant policy strides have been made over the last two decades, but effective conservation requires a dramatic acceleration in pace as well as an expansion of scope to include all shapes and sizes of these exceptional species,” Fordham said.

The study was published in the journal eLife on Tuesday.

Bat ray tangled in web










Photos via: Project Aware (top) and Andy Murch for Predators in Peril (above).

Alisha is a writer and researcher with Ring of Fire. You can follow her on Twitter @childoftheearth.