Marine predators flock to California coast
http://www.signonsandiego.com/news/2011/jun/22/california-cu...
Marine predators flock to California coast
New tracking study shows importance of coastal waters
By Mike Lee
10 a.m., June 22, 2011
After a decade of electronically tracking the Pacific Ocean’s top predators, scientists on Wednesday compared the waters off California to Africa’s
Serengeti Plain, famous for an abundance of lions, elephants and other charismatic species.
The unprecedented research effort involved dozens of scientists tagging more than 4,300 creatures and charting their movements from 2000 to 2009 as
part of the international Census of Marine Life. The latest in a string of papers based on the data was published Wednesday in the journal Nature by
scientists from San Diego to Nova Scotia.
It underscores the significance of the California Current Ecosystem and the importance of protecting iconic creatures from overfishing and pollution
in those waters because they influence the entire North Pacific. Study authors called for an aggressive international management effort to preserve
the biological hot spots they studied.
Tracking maps show the ocean’s top predators rely heavily on the 600-mile-wide band of ocean water that runs from British Columbia to Baja California.
They also illustrate how large numbers of species migrate seasonally to take advantage of warmer marine temperatures. In addition, tagged animals have
generated data that help describe subsurface conditions, and they have inspired scientists to think big about similar projects around the globe.
To read the analysis and see tracking maps, click here.
“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 deserts that animals avoid, and the migratory corridors that animals such as wildebeest use to travel from place to place?” said
Barbara Block, a study co-author at Stanford University. “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.”
While the overarching message of Wednesday’s study was hopeful, it comes against a gloomy backdrop. A report issued Tuesday by the United Nations said
fishing and other human stressors are degrading the world’s oceans more quickly than scientists had realized. The California Current itself is under
pressure from rising temperatures, increased acidification and decreasing oxygen but it remains a Main Street of the north Pacific Ocean.
Turtles tagged in Indonesia showed up off the West Coast of the mainland U.S., as did bluefin tuna from Japan, seabirds from New Zealand and salmon
sharks from Alaska.
“You kind of have this sense that the Pacific Ocean is this vast featureless space and the animals just wander about,” said Heidi Dewar, a study
co-author with the federal Southwest Fisheries Science Center in La Jolla. “But they have specific neighborhoods that they like to visit.”
People have tracked various marine species for hundreds or even thousands of years, but scientific knowledge about their life cycles, migration
pathways, residency patterns and population sizes still is fragmentary.
The Census of Marine Life is the most extensive assessment of its kind, engaging an estimated 2,700 scientists and creating more than 30 million
pieces of data that help explain how the ocean ecosystems function. Researchers involved with the international initiative have formally described
roughly 1,200 species, and 5,000 more are in the pipeline.
One of the research platforms involved tagging 23 top predators such as sharks, whales and sea birds in the Pacific Ocean with a variety of tracking
devices. It took 75 biologists, oceanographers, engineers and others to pull it off. Analysts spent the past two years synthesizing data.
Wednesday’s report marked the first time that all the species tracks were overlaid on the same map.
“Ten years ago, if you were looking at a map of what we knew about the movements of sharks, there would have been a few dots around the coast and
maybe Hawaii,” Dewar said. “Now we really are blanketing the Pacific with what we know.”
Scientists already had described the California Current as one five major regions of upwelling in the world. Upwelling is a phenomenon in which cold,
nutrient-rich water from the deep replaces relatively warm waters near the surface. That encourages the growth of phytoplankton, which forms a base
for a web of marine life. To read a recent story about that, click here.
Wednesday’s study helps unlock some of the secrets of an environment that seems to get more complex the more that scientists learn.
For instance, the research shows many highly migratory marine species return to the same ocean regions with what researchers called “astonishing
fidelity” to the places they were tagged and following a predictable seasonal pattern. “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,” Block said.
The study also allowed scientists to correlate temperature and chlorophyll concentrations to the presence of specific species, giving them better
predictive tools. Species making seasonal north-south migrations included bluefin tunas and yellowfin tunas; mako, white and salmon sharks; blue
whales; male elephant seals; and leatherback sea turtles.
“It’s like a big dance — the ocean is setting the rhythm and these different species are keeping time to the rhythm,” said study co-author Ian Jonsen
at Dalhousie University in Halifax, Canada.
One of the big questions raised by the paper is how predators will respond if that rhythm is altered by climate change, which evidence suggests
already is happening.
“That is something we don’t know,” Jonsen said.
But the impact of global warming should come into better focus now that other researchers around the world are looking at similar tracking projects.
“(We did) something on a level and size that had never been attempted,” said Dan Costa, a study co-author at the University of California Santa Cruz.
“We have changed the way people think.”
Some of those changes may result in new management programs. Dewar said tracking data could help reduce the ecological impact of commercial fisheries,
for instance by regulating zones that are most important for imperiled creatures such as leatherback turtles and reducing restrictions in areas that
don’t have high turtle traffic.
She and her co-authors hope their work generates international interest, perhaps though a UNESCO Marine World Heritage designation for the California
Current, and the development of an ecosystem-based management regime. Otherwise, they said, “biodiversity of this open-ocean wilderness will be
irreplaceably lost.”
Mike Lee: mike.lee@uniontrib.com; (619)293-2034; Follow on Twitter @sdutlee
\"The only thing necessary for the triumph of evil is for good men to do nothing\"
1961- JFK to Canadian parliament (Edmund Burke)
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