A team of fisheries researchers on Thursday reported data that has led to seven species of sharks and rays being added to the global list of threatened species.
Six more species of shark are under enough pressure to make the "red list" of threatened species maintained by the World Conservation Union, which revealed the results at a conference of the U.N. Convention on Biological Diversity in Bonn. Four of those will be listed as "vulnerable."
The pelagic stingray was also added following the research into the status of 21 species of sharks and rays.
Sonja Fordham, co-author of the study and a director of the Shark Alliance, a Belgium-based advocacy group, said that the sharks studied were chosen because they were most often harvested by fishermen on the high seas.
"Fishermen who usually go after other species are targeting sharks, looking to develop new markets," she told The Associated Press.
While some governments have recently introduced fishing regulations for sharks, there are no catch limits for sharks in international waters, she said. That lets fishermen exploit shark populations at a moment when they are increasingly valuable.
Demand for shark fin soup is growing in China, and Europeans have developed a taste for shark meat, the report found, noting that the thresher and shortfin mako shark species were among those targeted because of demand for their meat.
Regulations on sharks have lagged behind those for other fish, she suggested, because sharks are perceived as dangerous and because they are traditionally less desirable to fishermen than widely harvested species like tuna.
The paper appears in the latest edition of the journal "Aquatic Conservation: Marine and Freshwater Ecosystems."
Sharks and rays are particularly vulnerable to overfishing because most take many years to become sexually mature and have relatively few offspring.
"Fishery managers and regional, national and international officials have a real obligation to improve this situation," lead author Nicholas Dulvy, who is based at Simon Fraser University in Vancouver, Canada, said in a statement. "We are losing species at a rate 10 to 100 times greater than historic extinction rates."