"Great White Cafe" -Saving the World's Vanishing Shark Species

Once plentiful sharks are vanishing from the world's oceans, and some species are even at risk of extinction a marine biologist told fellow scientists at the annual conference of the American Association for the Advancement of Science.

A current assessment  by the World Conservation Union has found that many large shark species have declined by more than half due to increased demand for shark fins and meat, recreational shark fisheries, as well as tuna and swordfish fisheries, where millions of sharks are taken as bycatch each year.

"As a result of high and mostly unrestricted fishing pressure, many sharks are now considered to be at risk of extinction," said Julia Baum, a member of the IUCN's Shark Specialist Group. "Of particular concern is the scalloped hammerhead shark, an iconic coastal species, which will be listed on the 2008 IUCN Red List as globally 'endangered' due to overfishing and high demand for its valuable fins in the shark fin trade," said Baum.

Research at Dalhousie University over the past five years, conducted by Baum and the late Ransom Myers, demonstrated the magnitude of shark declines in the northwest Atlantic Ocean.

All species the team looked at had declined by over 50 percent since the early 1970s. For many large coastal shark species, the declines were much greater - tiger, scalloped hammerhead, bull and dusky shark populations have all plummeted by more than 95 percent.

The first complete IUCN Red List assessment of the status of all Mediterranean sharks and rays has revealed that 42 percent of the species are threatened with extinction. Overfishing, including bycatch, was identified as the main cause of decline by the study, which was released in November 2007.

"Our analysis reveal the Mediterranean Sea as one of the world's most dangerous places on Earth for sharks and rays," said Claudine Gibson, Program Officer for the IUCN Shark Specialist Group. "Bottom dwelling species appear to be at greatest risk in this region, due mainly to intense fishing of the seabed."

Peter Klimley, director of the Biotelemetry Laboratory at the University of California-Davis, has used electronic tags to track scalloped hammerhead sharks along their migration routes in the tropical Eastern Pacific Ocean. Their results suggest that these sharks speed between a series of "stepping stone" sites, near coastal island groups ranging from Mexico to Ecuador.

The great white shark, perhaps the most universally recognizable species in the ocean, also appears to return to a limited number of sites as part of its seasonal migration.

Salvador Jorgensen, a researcher at Stanford University's Hopkins Marine Station, has teamed with his colleagues in the Tagging of Pacific Predators program to tag nearly 150 great whites found near the coast of central California. In the winter, these sharks leave the seal rookeries where they feed all summer, and set off for warmer waters near one of two tropical "hotspots." One site between Hawaii and Mexico attracts so many of these giants, it has become known as "the white shark cafe."

"We started calling it the cafe  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 says. "Once they leave the cafe , they return year after year to the same exact spot along the coast, just as you might return to a favorite fishing hole."

For coastal species, a network of marine reserves also can be an effective strategy. In both cases, Baum sees consistent and tough enforcement as absolutely crucial.

"Many pelagic sharks are getting snuffed out from longliners that target tunas and swordfish, while deep sea sharks are caught in bottom trawls and gillnets," explains Lance Morgan, a marine scientist from the Marine Conservation Biology Institute.

"Sharks have nowhere left to hide in an ocean subject to widespread fishing. Catch limits, finning bans and a network of enforced marine reserves are all necessary conservation strategies to protect them."

Posted by Casey Kazan. Adapted from an American Association for the Advancement of Science release.