In 2008 the IUCN's Red List of threatened and endangered sharks will add five new species that live in the open ocean. The group believes 16 of 21 open-ocean shark and ray species are threatened or nearly threatened.
The situation may be worse for deep-water sharks.
Colin Simpfendorfer, a researcher at James Cook University in Queensland, Australia, said his new research suggests deep-water sharks, rays, and skates may take much longer to recover from overfishing than their shallow-water kin.
"On average, deep-water sharks are half as good at withstanding fishing pressure," Simpendorfer said.
"Deep-water shark fisheries could have rapid and substantial effects on shark populations."
But numbers are spotty, he said: Scientists have enough data to understand what's happening with only 13 of the 581 known deep-ocean species.
Stanford's Jorgensen and his colleagues tagged and tracked more than a hundred great white sharks along the central California coast.
The sharks have access to a year-round supply of seals and sea lions—but that's apparently not enough to keep them from voyaging.
The researchers have tracked the sharks to two winter hotspots: one off the Hawaiian coast and another at a point in the middle of the ocean, halfway between California and Hawaii.
Though they're not sure whether the draw is food or reproduction, they've dubbed the area the White Shark Café.
"We started calling it the café because that is where you might go to have a snack or maybe just to 'see and be seen.' We are not sure which," Jorgensen said in a statement.
"These animals appear again and again at very specific areas," he said. "This is really important in terms of management."
By figuring out sharks' migration routes and where the highly mobile fish congregate, researchers can provide valuable information to help fisheries managers decide which ocean regions are the highest priorities for protection.
UC Davis's Klimley and his team have also found that scalloped hammerhead sharks stop along a series of pre-established island sites between Mexico and Ecuador for extended periods of time.
Creating reserves around such islands will go a long way toward protecting hammerheads, he said, and "will provide the public with places for viewing sharks in their habitat."
The scalloped hammerhead—new on the 2008 IUCN list—is one of the most at-risk open-ocean species, said Julia Baum, a marine ecologist at Scripps Institution of Oceanography of the University of California San Diego.
No international limits exist on shark fishing, Baum said, though a United Nations resolution calls for catch limits and a strict ban on the practice of slicing off shark fins for use in soup. Finned sharks are often tossed back in the ocean to die.
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