Bonn, Germany  - Overfishing is leading to the extermination of many species of shark and ray in the world's oceans, according to a new international study presented Thursday to the UN Biodiversity Conference in Bonn.

Released to coincide with International Biodiversity Day, the study of the global status of 21 species of oceanic pelagic sharks and rays reveals that 11 of them are threatened with extinction.

The study, organized by the IUCN international conservation organization, calls on governments to take steps to halt the overfishing of the species.

The scientists from around the world found that the sharks and rays, including the Thresher shark, the Silky shark and the Shortfin mako, were facing extinction owing to targeted fishing for fins and meat.

Unintentional "bycatch" by other fisheries was also a serious problem.

"The traditional view of oceanic sharks and rays as fast and powerful too often leads to a misperception that they are resilient to fishing pressure," Sonja Fordham, co-author of the paper and member of the IUCN shark group, said.

The study noted the increasing demand for the delicacy shark fin soup, which was being driven by growing Asian economies, and the resultant waste when the rest of the shark was simply thrown away.

Shark and ray species often take several years to reach sexual maturity, have relatively few young and are thus particularly vulnerable to overfishing.

The IUCN called on governments to establish and enforce shark catch limits, halt the practice of removing fins and discarding the rest, cut the bycatch and to invest in further research into populations.

The study is published in the latest edition of Aquatic Conservation: Marine and Freshwater Ecosystems. (dpa)