A quarter of the world’s sharks and rays are probably threatened with extinction, according to the most extensive assessment of the marine species.

Thresher sharks, sawfishes and angel sharks are the most threatened families, according to a study by the International Union for the Conservation of Nature, which publishes the Red List of endangered species. A total of 25 species had the highest risk level and were deemed “critically endangered.”

“Our analysis shows that sharks and their relatives are facing an alarmingly elevated risk of extinction,” said Nick Dulvy, a researcher at Simon Fraser University in British Columbia, Canada, and co-chair of the IUCN’s Shark Specialist Group. “In greatest peril are the largest species of rays and sharks, especially those living in shallow water that is accessible to fisheries.”

Overfishing is the main threat faced by the species, with much of the sharks and rays caught unintentionally, according to the union. Intentional killing of the creatures due to the perceived danger they bring, and the global market for shark fins used in soup are other factors, it said.

The researchers examined 1,041 species of rays, sharks and so called chimera that are closely-related. They determined 25 are critically endangered, 43 are endangered and 113 are vulnerable to extinction. Almost half of the species — 487 — had insufficient data to determine a category.

By applying the findings for the data-sufficient fish to the less-studied ones, the researchers said that 249 species, or 24 percent of the total, are likely to be threatened in one form or another.

The study, a product of the work of 302 researchers in 64 nations, was published Jan. 22 in the journal eLIFE.

In a time of both misinformation and too much information, quality journalism is more crucial than ever.
By subscribing, you can help us get the story right.