West Coast boasts underwater Serengeti, study finds

How many fish can we harvest to feed growing populations without entirely depleting ocean reserves? What kind of damage did last year’s oil spill actually cause to the Gulf of Mexico’s wildlife? And when is it safest to swim in waters that man-eating sharks sometimes haunt? The way to unlock these and other key secrets of the deep: Attach electronic tags to oceangoing creatures and send them out to do the research.

That’s what a team of researchers did in a decade-long project that shines unprecedented light under the waters of the world’s biggest ocean — the Pacific — and proves the worth of a methodology that can be adapted for use elsewhere around the world.

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A new study found that many species of Pacific predators stick to familiar routes each season. View maps of the paths some of the marine creatures traveled.

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The Census of Marine Life’s Tagging of Pacific Predators (TOPP) project, published Wednesday in the online version of the journal Nature, deployed 4,036 tags on 23 species of ocean predators, a group that includes several seabirds.

It reveals that the eastern Pacific Ocean is akin to Africa’s Serengeti, teeming with wildlife and crisscrossed by migration corridors used by sharks and seabirds. But the census’s greater value might be in advancing knowledge of a largely uncharted underwater world on which we increasingly depend.

“It’s precedent-setting. It’s a tremendous tool for conservation and management,” said Jesse Ausubel, vice president of the Alfred P. Sloan Foundation and co-founder of the Census of Marine Life. “We were literally blind. We can now see. We know what’s underneath now.”

The findings would be “as if from space we can see the people on the D.C. Metro, and not only the D.C. Metro, but the people on Amtrak and at Dulles Airport and Reagan National Airport and BWI,” he said.

Now, for the creatures, “you suddenly see these incredible patterns by these commuters, long distance and short distance,” he said.

For example, shearwater seabirds tagged off New Zealand made a 262-day, 39,790-mile round-trip journey in a figure-eight pattern, the longest animal migration ever recorded electronically at the time.

Elephant seals won another distinction in the project: At 5,492 feet, one seal dove deeper than any other tagged animal in the study.

Seventy-five researchers from five countries collaborated on the project, which cost $20 million to $25 million, analyzing the ocean’s chlorophyll content and tracking the nature of the water through which the predators moved.

“Just off the West Coast may be one of the greatest hot spots for open ocean predators in the world,” said Barbara Block of Stanford University’s Hopkins Marine Station, the lead author of the study along with Daniel Costa, professor of ecology and evolutionary biology at the University of California at Santa Cruz.

In a phone interview, Block said she was struck by how each spring the rich nutrients in the cool water along the California Current, which flows south along the West Coast of the United States, Canada and Mexico, drew an array of animals to the same place. Young bluefin tuna make their way from Japan for the area’s soup of krill, sardines, anchovies and squid, as do leatherback turtles from Indonesia and sooty shearwater birds from New Zealand.