June 24, 2011
Researchers Complete Pacific Ocean Predators Census
According to new research from the Census of Marine Life Tagging of Pacific Predators (TOPP), two expanses of the North Pacific Ocean are attracting an array of marine predators in predictable seasonal patterns.
The new report archives the TOPP program's effort to track top marine predator movements in the Pacific Ocean.
The study found major hot spots for large marine predators that exist in the California Current, which flows south along the U.S. 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.
"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," the authors wrote in the journal Nature.
"Knowing where and when species overlap is valuable information for efforts to manage and protect critical species and ecosystems."
The researchers launched the project in 2000 as part of the Census of Marine Life. TOPP became the world's largest-ever biologging study, eventually involving over 75 biologists, oceanographers, engineers and computer scientists across five countries.
Barbara Block of Stanford University's Hopkins Marine Station said in a statement: "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 project tagged 23 species and revealed how migrations and habitat preferences overlap. It placed 4,306 electronic tags on the species, helping the researchers to collect a huge amount of data.
The scientists spent two years synthesizing data sets with advanced statistical techniques and discerned intersecting hotspots and highways of ocean life.
"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" Dr. Ian Jonsen of Dalhousie University said in a statement.
The results suggest water temperature plays a key role to the seasonal migrations of many species.
The large ecosystem was defined by the California Current, where cool, nutrient-rich water moves south along the U.S. west coast.
The study found that the Current plays a role as a vast marine savanna to a large number of whales, sharks, seals, seabirds, turtles and tunas every year.
It shows many highly migratory marine species return to the same ocean regions, following a predictable seasonal pattern.
Block said in a statement: "For me, the homing capacity of species which routinely return to the California Current or shelf waters of North America has been the biggest surprise."
The study also found that some species have more difficulty with poor ocean productivity. Coastal birds depend on krill, and during an El Nino in 2006 to 2007, most of the hatching failed, the researchers said.
The TOPP study was the first ocean basin-scale study of marine predator distribution and movement ever conducted.
The study shows the importance of apex predators in different ecosystems, noting how the loss of bluefin tuna and porbeagle sharks in the Atlantic Ocean contributed to the near-extinction of cod and similar species.
The authors said for the first time, the TOPP team has been able to link the movements of tunas, sharks and blue whales north and south along the southwestern U.S. coastline with seasonal changes in temperature and chlorophyll concentrations.
"Using satellite observations of temperature and chlorophyll concentrations alone, we can now predict when and where individual species are likely to be in a given ocean region and begin to understand factors that control their movements. This is fundamental to the concept of ecosystem-based management," Daniel Costa, professor of ecology and evolutionary biology at the University of California, said in a statement.
Barbara Block of Stanford University was lead author for the Nature paper. Other institutions participating in the study with OSU and Stanford included Dalhousie University, San Jose State University, NOAA Southwest Fisheries Science Center, University of California-Santa Cruz, and the Inter-American Tropical Tuna Commission.
Image Caption: This blue whale was encountered during a tagging expedition by the Oregon State University Marine Mammal Institute in 2006 near the Channel Islands of California. (Photo by Craig Hayslip, courtesy of OSU Marine Mammal Institute)
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