Teeming With Life, Pacific's California Current likened to Africa's Serengeti Plain

Like the vast African plains, two huge expanses of the North Pacific Ocean are major corridors of life, attracting an array of marine predators in predictable seasonal patterns, according to final results from the Census of Marine Life Tagging of Pacific Predators (TOPP) project published today in the journal Nature. The paper culminates the TOPP program's decade-long effort to track top marine predator movements in the Pacific Ocean. It presents for the first time the results for all 23 tagged species and reveals how migrations and habitat preferences overlap -- a remarkable picture of critical marine life pathways and habitats.

The study found that major hot spots for large marine predators are the California Current, which flows south along the US west coast, and a trans-oceanic migration highway called the North Pacific Transition Zone, which connects the western and eastern Pacific on the boundary between cold sub-arctic water and warmer subtropical water -- about halfway between Hawaii and Alaska.

"These are the oceanic areas where food is most abundant, and it's driven by high primary productivity at the base of the food chain -- these areas are the savanna grasslands of the sea," say co-authors and project originators Barbara Block of Stanford University’s Hopkins Marine Station and Daniel Costa, professor of ecology and evolutionary biology at the University of California, Santa Cruz.

"Knowing where and when species overlap is valuable information for efforts to manage and protect critical species and ecosystems."

Drs. Costa and Block were joined by Steven Bograd of the NOAA Southwest Fisheries Science Center, Randy Kochevar of Stanford University and others to launch the project in 2000 as part of the Census of Marine Life, a 10-year research initiative that investigated the diversity, distribution, and abundance of marine life in the global ocean. TOPP became the world’s largest-ever biologging study, eventually involving more than 75 biologists, oceanographers, engineers and computer scientists across five countries.

Says Dr. Block: “It’s been a bit like looking down on the African savanna and trying to figure out: Where are the watering holes that a zebra and a cheetah might use? Where are the fertile valleys? Where are the deserts that animals avoid, and the migratory corridors that animals such as wildebeest use to travel from place to place? We’ve come to a vast oceanic realm in the Pacific and answered these questions for animals as diverse as bluefin tuna, blue whales and leatherback sea turtles.”

"This is the first publication that pulls all of the pieces together in one place," says Dr. Costa, who oversaw the tracking of marine mammals, birds, and turtles. "We brought together a large team of investigators to study diverse species and look at how these organisms use the ocean. It is an unprecedented examination of so many species over such a large scale."

The scientists used a variety of technologies to track the locations of different species as well as environmental variables such as water temperature, salinity, and depth. Altogether, the project deployed 4,306 electronic tags on the 23 species, yielding a huge amount of data for analysis.

Working with Census scientists at Dalhousie University in Halifax, Canada and its Future of Marine Animal Populations project (FMAP), the scientists spent two years synthesizing data sets with advanced statistical techniques and discerned intersecting hotspots and highways of ocean life and how marine conditions influenced where animals hang out.

“One of the challenges for this study was to take distinctly different types of location data – some very precise from ARGOS satellites and others far less precise from ambient light level readings and bring them together using a powerful statistical framework that enabled identification of high use areas” says Dalhousie’s Dr. Ian Jonsen.

The results suggest water temperature is key to the seasonal migrations of many species. This was particularly evident in the large marine ecosystem defined by the California Current, where cool, nutrient-rich water moves south along the US west coast.

The study reveals the Current as a vast marine savanna to and within which a large number of whales, sharks, seals, seabirds, turtles and tunas migrate loyaly every year.