Nine species of shark are to be added to the IUCN red list when it is revised in October, joining the 126 shark species already listed.
Particularly notable among the species to be added is the Scalloped hammerhead shark, Sphyrna lewini, which will be listed as ~endangered .
This species was previously considered to be abundant, and will be joined by Short-fin mako shark, Smooth hammerhead, Big-eye thresher and Common thresher, Silky, Tiger, Bull and Dusky sharks.
At their last review, the sharks were not considered to be at threat. However, new research carried out by Dr Julia Baum of Scripps Institution of Oceanography, California, has revealed rapid declines in numbers.
Dr Baum reports that numbers of Scalloped hammerhead sharks declined by 98% along the US Atlantic coast between 1970 and 2005, while shark populations on a whole declined by 50%.
Right now the oceans are being emptied of sharks, and the scale of the problem is global, Dr Baum said. If we continue in the way we are going, we are looking at a really high risk of extinction for some of these species within the next few decades.
Sphyrna lewini, Scalloped hammerhead shark. (LittleGreenMan, Creative Commons).
It is believed that the high value of shark fins, combined with the by-catch of sharks by commercial tuna fisheries, are the major causes of the declining numbers. Conservation efforts are to include the protection of ~hotspots where sharks congregate during migration, while the United Nations recently agreed to limit shark fishing in international waters.
Hammerhead sharks are not evenly dispersed throughout the seas, but concentrated at seamounts and offshore islands, said Peter Klimley of the University of California. Hence, enforcing reserves around these areas will go far in protecting these species and will provide the public with places for viewing sharks in their habitat.
However, the slow growth rates of Scalloped hammerhead sharks, which take 16 years to mature, will mean that recovery will be difficult.
The perception used to be that really wide ranging species like this couldn t become endangered, as while they might be threatened in one area they surely wouldn t be threatened in every area, said Dr Baum. We re now learning that that s not the case.