for National Geographic News
Not all Atlantic bluefin tuna are homebodies, scientists have learned.
That means officials will have to rethink present management plans designed to prevent overfishing of the species, say the authors of a study that provides the best knowledge so far about the Atlantic bluefin's migratory and spawning patterns.
The results showed that bluefin travel freely throughout a much wider range of the Atlantic than previously thought.
Until now, they had been regarded as two separate populations, concentrated in the Western or the Eastern Atlantic.
An organization established to manage commercial harvesting of bluefin and other Atlantic tuna, the International Commission for the Conservation of Atlantic Tunas (ICCAT) in Madrid, Spain, recognized two populations of bluefin when it imposed quotas on catches in an attempt to curb overfishing.
Currently, the quotas for Western Atlantic fisheries is one-twelfth the quota for Eastern Atlantic fisheries, which include the Mediterranean Sea.
But when researchers used an innovative tagging technique to track the fishes' movement, they found that eastern and western populations of bluefin tuna don't pay much attention to the ICCAT's boundaries.
"Our study shows that western bluefin tuna are vulnerable to all bluefin tuna fisheries. They are currently managed as if they are only vulnerable to western fisheries," said Barbara Block, a marine scientist at Stanford University in Palo Alto, California. She is co-author of a paper on the findings published in today's issue of Science.
Overfishing a Problem
On both sides of the Atlantic the bluefin is a prized delicacy, particularly among connoisseurs of sushi and sashimi.
Atlantic bluefin tuna, which can grow ten feet (305 centimeters) long and weigh up to 1,500 pounds (680 kilograms), routinely fetch premium prices: from U.S. $8 a pound to as much as $45 a pound.
In January, a single fish weighing 444 pounds (201 kilograms) sold at auction in a Tokyo, Japan, seafood market for U.S. $175,000.
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