BENEATH the waves of the Pacific Ocean, there鈥檚 a marine superhighway that
stretches more than 8000 kilometres from Japan to California. It is lined with
the marine equivalent of cheap diners, and it is where all the big beasts of the
sea love to go on the prowl.
Go out there almost any day of the year and you鈥檒l find albacore tuna,
loggerhead turtles and female elephant seals on their vast migrations.
Meanwhile, albatrosses cruise the airways overhead.
Researchers discovered the pivotal role that the Pacific marine superhighway
plays in the lives of many of the movers and shakers of the ocean with the help
of new electronic tags that allow researchers to follow their long journeys
using satellite links.
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鈥淏iologists are for the first time seeing the ocean from the perspective of
large oceanic animals. They turn out to be more wide-ranging than previously
thought, but feed in a small number of very restricted areas,鈥� says Jeffrey
Polovina of the National Oceanic and Atmospheric Administration, who presented
the findings this week.
The marine superhighway is like an oceanic weather front where cold,
nutrient-rich waters from the north meet the warmer, nutrient-poor tropical
waters coming up from the south. The convergence creates a biological bonanza in
sharp contrast to most of the rest of the ocean.
Marine mammals, reptiles and large migrating fish take this route to ensure
their food supplies while crossing the ocean. Loggerhead turtles are the
jet-setters of the reptilian world鈥攖hey nest in Japan but grow fat amid
the surf off California. To get from one place to the other they take the
highway, snacking en route on crabs and jellyfish.
鈥淯ntil now, nothing was known about the migration and foraging habitat of
juvenile loggerheads, except that they were occasionally caught in fishing gear
in the central North Pacific,鈥� says Polovina.
Similarly, albacore tuna dine on squid and saury along the front. And,
reports tag analyst Daniel Costa of the Long Marine Laboratory at Santa Cruz,
female elephant seals eat their kill on the superhighway while the males head
far north to the Aleutian Islands to feed.
Unlike highways on land, this marine thoroughfare is mobile. In winter it
takes a path roughly between Japan and southern California, while in summer it
shifts 1000 kilometres north. It鈥檚 the longest of a number of similar fronts in
the Pacific and other oceans.
None of the tagged animals was caught specifically for the experiments, says
Polovina. They were freed from long lines on commercial fishing boats before
being tagged and released.
