January 23, 2014
A Quarter Of Sharks And Rays Are Threatened By Extinction
Lee Rannals for redOrbit.com - Your Universe Online
According to a new study published in eLife, a quarter of the world’s sharks and rays face extinction within the next few decades due to overfishing. The latest study is the first to survey the cartilaginous fish status throughout coastal seas and oceans, revealing that 249 out of 1,041 sharks and rays fall under three threatened categories on the International Union for Conservation of Nature's (IUCN) Red List.“We now know that many species of sharks and rays, not just the charismatic white sharks, face extinction across the ice-free seas of the world,” said Nick Dulvy, a Simon Fraser University (SFU) Canada Research Chair in Marine Biodiversity and Conservation in British Columbia. “There are no real sanctuaries for sharks where they are safe from overfishing.”
The researchers used the IUCN Red List and were able to classify 107 species of rays and 74 species of sharks as threatened. Only 23 percent of species were labeled as being Least Concern. They used all available data on distribution, catch, abundance, population trends, habitat use, life histories, threats and conservation measures.
The team was able to identify some main areas where sharks and rays are most threatened, including the Indo-Pacific, the Red Sea and the Mediterranean Sea.
“In the most peril are the largest species of rays and sharks, especially those living in relatively shallow water that is accessible to fisheries. The combined effects of overexploitation—especially for the lucrative shark fin soup market—and habit degradation are most severe for the 90 species found in freshwater,” Dulvy said.
The team found that rays are generally worse off than sharks, and unless efforts are made to protect these fish then there is a risk that one day sharks and rays may not exist in the wild. The disappearance of sharks would have an impact on the marine ecosystem as a whole.
“The biggest species tend to have the greatest predatory role. The loss of top or apex predators cascades throughout marine ecosystems,” says Dulvy.
IUCN’s Shark Specialist Group is asking governments to safeguard sharks and rays by placing a prohibition on catching the most threatened species, as well as protecting key habitats. Losing these species could end a chapter in the history of evolution.
“They are the only living representatives of the first lineage to have jaws, brains, placentas and the modern immune system of vertebrates,” Dulvy, who co-chairs the IUCN SSG, said.