Sharks swim closer to extinction

Specialists with IUCN (formerly the World Conservation Union) found that 11 species are on the high-risk list, with five more showing signs of decline.

Sharks are particularly affected by over-fishing as they reproduce slowly.

The scientists are calling for global catch limits, an end to the practice of removing fins, and measures to minimise incidental catches (bycatch).

"There's this idea that because these are widely ranging species, they're more resilient to fishing pressure," said Sonja Fordham, deputy chair of the IUCN Shark Specialist Group (SSG) and policy director for the Shark Alliance conservation group.

"In fact they're becoming species of serious concern because there are no international catch limits for sharks. There are intense fisheries on the oceans, and they remain pretty much unprotected."

New threats

The SSG assessed data on the 21 species of sharks and their close cousins, the rays, that swim in upper portions of the open ocean where they are exposed to fishing fleets.

Of the 21, one - the giant devilray - is assessed as Endangered, and 10 are Vulnerable.

A further five are listed as Near Threatened, which means the signs of decline are not serious enough yet to merit a full listing.

The classifications are based on a range of criteria that look at past or forecast declines in population size. For example, a population shrinking by 50% in 10 years would usually qualify as Endangered.

Some of these species have been assessed before; but for others, including the three species of thresher sharks with their spectacularly long tails, the dangerlisting is new.