Scientists say these hotspots - off the east coasts of the US, Australia, and Sri Lanka; south of Hawaii; and in the South-Eastern Pacific ?provide new insight into the structure of life in the open ocean and a focus for conservation efforts. Perhaps most surprising is the discovery that patterns of big fish diversity match those for tiny zooplankton, and both are linked to sea surface temperature. "This is the great joy of science," says first author Boris Worm. "It is like solving a giant puzzle and seeing the night sky in constellations for the first time ?even as the stars are blinking out. It's beautiful ?and tragic at the same time."
In a sequel to their groundbreaking study in Nature in 2003, showing the depletion of 90% of the big fish in the ocean, co-authors Boris Worm and Ransom Myers of Dalhousie University reveal that overfishing has not only reduced the number of fish in the sea, but also the variety: the diversity of tuna, marlins, and swordfish in the oceans has declined by up to 50% in the last 50 years.
"Everywhere you go, in every ocean basin, our "hotspots" today are only relics of what was once there," says Worm. "It really hurts to see this."
In the first global mapping of predatory fish diversity in the open ocean, the international team of scientists show where the diversity of the big fish was greatest 50 years ago ?and the dramatic contrast of what remains today. The ocean off Northwest Australia, for example, was