软骨鱼类未来几十年濒临灭绝

One quarter of the world's cartilaginous（软骨的） fish, namely sharks and rays, face extinction¹ within the next few decades, according to the first study to systematically² and globally assess their fate. The International Union for Conservation of Nature's (IUCN's) Shark Specialist Group (SSG), co-chaired by Nick Dulvy, a Simon Fraser University (SFU) Canada Research Chair in Marine³ Biodiversity and Conservation in British Columbia, conducted the study.   It was published ineLife journal today.   Previous studies have documented local overfishing of some populations of sharks and rays. But this is the first one to survey their status through out coastal⁴ seas and oceans. It reveals that one-quarter (249) of 1,041 known shark, ray and chimaera（银鲛） species globally fall under three threatened categories on the 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," says Dulvy. "There are no real sanctuaries⁵ for sharks where they are safe from overfishing."   Over two decades, the authors applied⁶ the IUCN's Red List categories and criteria⁷ to the 1,041 species at 17 workshops involving more than 300 experts. They incorporated all available information on distribution, catch, abundance, population trends, habitat use, life histories, threats and conservation measures.   Sharks and rays are at substantially higher risk of extinction than many other animals and have the lowest percentage of species considered safe. Using the IUCN Red List, the authors classified 107 species of rays (including skates) and 74 species of sharks as threatened. Just 23 percent of species were labeled as being Least Concern.   The authors identified two main hotspots for shark and ray depletion⁸ -- the Indo-Pacific (particularly the Gulf⁹ of Thailand), the Red Sea and the Mediterranean¹⁰ Sea.   "In the most peril¹¹ are the largest species of rays and sharks, especially those living in relatively¹² shallow water that is accessible to fisheries. The combined effects of overexploitation -- especially for the lucrative¹³ shark fin¹⁴ soup market -- and habit degradation¹⁵ are most severe for the 90 species found in freshwater.   "A whole bunch of wildly charismatic species is at risk. Rays, including the majestic¹⁶ manta and devil rays, are generally worse off than sharks. Unless binding#p#分页标题#e#¹⁷ commitments to protect these fish are made now, there is a real risk that our grandchildren won't see sharks and rays in the wild."   Losing these fish will be like losing whole chapters of our evolutionary¹⁸ history says Dulvy. "They are the only living representatives of the first lineage to have jaws¹⁹, brains, placentas（胎盘） and the modern immune system of vertebrates."   The potential loss of the largest species is frightening for many reasons, says Dulvy. "The biggest species tend to have the greatest predatory role. The loss of top or apex²⁰（顶点，尖端） predators²¹ cascades²² throughout marine ecosystems²³."   The IUCN SSG is calling on governments to safeguard sharks, rays and chimaeras through a variety of measures, including the following: prohibition²⁴ on catching²⁵ the most threatened species, science-based fisheries quotas²⁶, protection of key habitats and improved enforcement.