To save or savor? It's decision time for Atlantic bluefin tuna

Giant bluefin tuna are in trouble, primarily because the powerful muscles that propel their extensive ocean migrations come with an Achilles' heel: They're tasty.

Prized by sushi lovers for their savory succulence and by fishermen for the incomparable price they command-one 607-pound fish fetched over $90 per pound at a January auction in Tokyo-all three species of bluefins have seen their population plummet in the past 50 years thanks to worldwide demand.

However, there is hope for bluefin, as new advances fueled by modern technologies in ocean science may be clarifying how best to manage Atlantic bluefin, according to Barbara Block, the Charles and Elizabeth Prothro Professor in Marine Sciences at Stanford University's Hopkins Marine Station. Block is scheduled to discuss her work during a press briefing scheduled for 8 a.m. Monday, Feb. 18, at the American Association for the Advancement of Science (AAAS) annual meeting in Boston. She also will discuss her work during a seminar at 9:15 a.m. Monday, Feb. 18.

Block has spent more than a decade tagging Atlantic bluefin tunas and tracking their travels. She and her team from Hopkins Marine Station and the Monterey Bay Aquarium have spent years at sea on a project called "Tag A Giant (TAG)," implanting 995 electronic tags in bluefin tunas. That is no small accomplishment, considering that giant bluefin can grow to 1,500 pounds, live in offshore waters and must be hauled onto boats to be measured, implanted with sophisticated electronic tags or have fin clips for DNA analysis removed.

Block and her students have uncovered remarkable details about the journeys of these giant fish, which can swim thousands of miles in a year and dive almost a mile below the surface. What she has learned is guiding decisions made by international managers and may lay the foundation for taking actions needed to bring the Gulf of Mexico bluefin population back.

The TAG team's research has shown that bluefin tuna tagged in the West Atlantic are composed of two populations, one that forages in the North Atlantic and moves primarily into the Mediterranean Sea to breed, and another that tends to swim on the North American side of the ocean while spawning exclusively in the Gulf of Mexico.

Genetic analyses conducted by marine biologist Andre Boustany and research associate Carol Reeb, both members of Block's team at Hopkins Marine Station, confirmed that the two North Atlantic populations are genetically distinct.

Block learned something else as well.

"Our tagging and genetic data reveal that while there are separate bluefin tuna populations, significant mixing exists across the North Atlantic," she said. Mixing takes place in foraging areas in the western, eastern and central Atlantic; the central region had long been thought to be a no man's land that separated the two fisheries.

The mixing of the tuna populations on feeding grounds is raising serious questions about current fisheries-management practices-and raising concerns about how many Gulf of Mexico-spawned fish are actually left.