Shark Superhighways

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The world’s sharks are disappearing. These fearsome yet charismatic fish continue to fall victim to overfishing and many are now at risk of extinction as a result.

New research shows that open-ocean sharks are particularly threatened from overfishing, and other work shows that the deeper sharks live, the longer it takes for their populations to recover.

A panel of researchers will discuss these insights, as well as strategies for shark conservation, at a press conference at the American Association for the Advancement of Science (AAAS) Annual Meeting in Boston, MA on February 17.

Sharks can evoke an image of nomadic loners, patrolling the high seas aimlessly in search of prey.

However, new research suggests that shark migration is anything but random, and that these efficient swimmers instead move along fixed “superhighway” routes between well-established gathering places.

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.

“Hammerhead sharks are not evenly dispersed throughout the seas, but concentrated at seamounts and offshore islands,” Klimley says.

“Hence, enforcing reserves around these areas will go far to protecting to these species, and will provide the public with places for viewing sharks in their habitat.”

The Scalloped Hammerhead is not alone in its habits. 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 (TOPP) 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 caf