The devastation being wrought on shark populations by fishing is likely to run to 100 million killed a year and may be as large as 270 million per year, with many species being killed faster than they can breed.
This is according to a new study that attempts to estimate the global catch of sharks and other members of the chondrichthyan fish family, such as skates and rays.
Sharks are either caught accidentally by boats fishing for other species or directly targeted, especially for the lucrative trade in their fins in the Far East. Their slow growth rates make this a source of increasing concern for researchers and conservationists.
Boris Worm of Dalhousie University in Halifax, Canada, and his colleagues compiled data from official sources and the scientific literature to estimate that around 100 million sharks were killed by fishing in 2000, and around 97 million were killed in 2010. Worm and his team acknowledge that their numbers should be treated cautiously given the huge uncertainties involved. The probable range for the true number of sharks killed is between 63 million and 273 million per year, they write in Marine Policy.
However, their numbers suggest that between 6.4% and 7.9% of all shark populations are being killed each year, a figure significantly higher than the 4.9% at which populations are thought to recover.
“Protective measures have to be scaled up significantly in order to avoid further depletion and the possible extinction of sharks, with largely unknown effects on marine ecosystems around the world,” they write.
The study comes ahead of votes at the CITES meeting in Bangkok, where some species of shark made be granted additional protection under international trade regulations (see ‘Tusk tracking will tackle illegal trade’). It was funded by the US National Science Foundation, the Natural Science and Engineering Research Council of Canada and the Pew Charitable Trusts non-governmental organization, which is pushing for enhanced protection of sharks at CITES.