A diverse collection of world travelers from as far away as New Zealand and Indonesia have found a hot spot on the West Coast. But to join them, you'll have to head out to sea.
Outfitted with tracking tags, 23 species of ocean predators -- including tunas, sharks, sea turtles, seals and whales -- have shown that the West Coast of North America, and California in particular, is a popular biological gathering place.
Although sea turtles and whales don't normally come to mind when thinking about predators, they do eat fish, krill and jellies -- and thus were included in the monitoring effort.
This survey of predators at the top of the food chain was part of the global Census of Marine Life, which concluded last year. Scientists with the Tagging of Pacific Predators, or TOPP, project deployed more than 4,000 tags from 2000 to 2009 to figure out where these animals spent their time.
"There's been a lot of tagging of animals as individual species," said Barbara Block, a professor at Stanford University and lead author of a study describing the predator survey published Wednesday in Nature. But what set this study apart, Block said, was the idea of looking at multiple species at the same time -- taking a more comprehensive ecological view of what was happening on California's watery doorstep.
Block and her colleagues discovered two key areas in the Pacific Ocean that supported a complex and robust ecosystem -- the California Current large marine ecosystem and the North Pacific transition zone.
The North Pacific transition zone is a migration highway in which sleek commuters such as bluefin tuna eat their way across the Pacific, eventually arriving off the West Coast.
The California Current large marine ecosystem resembles Africa's Serengeti plain in the richness of life it supports, Block said.
It extends as far as 230 miles from the West Coast, running from Canada to Mexico. It's a seasonal area, defined by predators that move along California's coast, following changing ocean temperatures and chasing food.
The ecosystem includes the California Current, which fuels a nutrient-rich food web that draws predators in search of tasty morsels such as anchovies, sardines, krill and squid.
The TOPP project used five kinds of tracking tags to simultaneously follow multiple species. All of them recorded an animal's location.
But fancier tags also logged habitat features such as salinity, seawater temperature and depth. Other tags transmitted real-time positions using GPS technology, similar to a cell phone.
The study also gave researchers a glimpse into how animals interacted. Related species, such as bluefin and yellowfin tuna, made use of the same general areas. But because bluefin tuna are more tolerant of the cold, they ranged farther north than yellowfin.
Data on ocean characteristics, including temperature, were key in determining the aspects of the environment important to these predators, said Steven Bograd, an oceanographer with the National Oceanic and Atmospheric Administration's Southwest Fisheries Science Center and one of the authors of the Nature study.
As is the case with many terrestrial animals, temperature can put the brakes on how far marine animals roam. Too cold, and the heart and other muscles don't work as well. Too warm, and they can overheat.
Such details helped scientists figure out that some species traveled much farther than previously thought. Sooty shearwaters took Bograd by surprise when he saw that the seabirds flew all the way from New Zealand to feed off the coast of California.
Tracking these movements gave researchers an idea of how long an animal spends in one place, how it gets from point A to point B and where it goes when it heads to open water.
"We have a very intact ecosystem off shore," Block said.
But she cautions that it isn't pristine. Although our patch of the Pacific is wilder than anyone thought, we need to make sure it stays that way.
"The richness is still a blessing," said Jesse Ausubel, vice president of the Alfred P. Sloan Foundation, one of the organizations that funded the Census of Marine Life. "And it's one I hope humanity doesn't squander."
Contact Jane J. Lee at 408-920-5064.