Up to 25 percent of all the world's sharks and rays may be wiped out in only a few years, according to a global study.

The "Red List of Threatened Species," issued by the Switzerland-based International Union for Conservation of Nature, sharks, rays and chimaeras are at a markedly higher risk than most other types of animals and -- with only 23 percent of the group listed in the report's "Least Concern" category -- have the lowest percentage of species considered safe.

The new data, which analyzed the conservation status of 1,041 shark, ray and closely related chimaera species and found rays at a higher risk than sharks, are part of the first-ever global analysis of these species carried out by the IUCN's Shark Specialist Group.

Marking the 50th year of the "Red List," the study, a result of a collaboration of 302 experts from 64 countries, was published Jan. 21 in the journal eLIFE.

"Our analysis shows that sharks and their relatives are facing an alarmingly elevated risk of extinction," Dr. Nick Dulvy, co-chair of the shark study group and Canada Research Chair at Simon Fraser University in British Columbia, said in a release. "In greatest peril are the largest species of rays and sharks, especially those living in shallow water that is accessible to fisheries."

The report named overfishing as the species' main threat.

Reported catches of sharks, rays and chimaeras peaked in 2003 even as it's generally assumed actual catches are likely to be greatly under-reported.

"Surprisingly, we have found that the rays, including sawfish, guitarfish, stingrays, and wedgefish, are generally worse off than the sharks, with five out of the seven most threatened families made up of rays," said Dr. Colin Simpfendorfer, SSG co-chair and professor of environmental science at James Cook University in Queensland, Australia.

"While public, media and government attention to the plight of sharks is growing, the widespread depletion of rays is largely unnoticed. Conservation action for rays is lagging far behind, which only heightens our concern for this species group," he said.

The global market for shark fins, used in shark fin soup, as well as shark and ray meat and medicines made from rays, contributes significantly to the depletion of not only sharks but also some rays with valuable fins, such as guitarfish.

The Indo-Pacific, particularly the Gulf of Thailand and the Mediterranean Sea are the two critical areas where the depletion of sharks and rays is most dramatic.

Said Sonja Fordham, SSG deputy chair and president of the Washington, DC-based Shark Advocates International project: "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. Our analysis clearly demonstrates that the need for such action is urgent."