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Already Imperiled Bluefin Tuna Threatened by Spill

Apr 30, 2010 – 2:50 PM
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Gregory Mone

Gregory Mone Contributor

(April 30) -- The massive oil spill in the Gulf of Mexico could not have happened at a worse time, or in a worse spot, for the Atlantic bluefin tuna. More than 600 species are considered to be at risk due to the sunken rig, which is gushing oil into the water at a rate of 210,000 gallons per day. But this is an especially sensitive period for the bluefin.

"The giant bluefin only show up for about a month, and this is the time they show up," Stanford University marine biologist Barbara Block told AOL News. "Bluefin tuna are moving to the Gulf of Mexico exactly right now to spawn." Plus, she said, the spill is centered around one of the preferred breeding areas. "Many of the tuna go exactly to that region."

Since 1996, Block has been leading a project called Tag-a-Giant (TAG), in which scientists tag bluefin tuna with small devices that enable the researchers to chart the movements of the fish over a period of years. Block and her group have tracked more than 1,000 bluefin. It was that research that revealed that the Atlantic bluefin tuna, which can grow to 1,500 pounds, regularly travels across the ocean and typically returns to spawn in the Gulf at this time every year.

The spawning periods are critical because the bluefin population isn't exactly booming. "The population has declined 80 percent to 90 percent of what its original spawning biomass was," Block said. But recent efforts to have the bluefin categorized as an endangered species failed.

Until this spill, it looked like the sushi craze was the fish's biggest threat. "Now, just when you need it to have a nice spring so that it can spawn," she said, "you have this accident."

The fishes' attraction to the Gulf region likely stems from its unique geography, Block said. The spawning area lies above an area where the long, flat continental shelf extends out from the Louisiana coast, then drops down a dramatic slope. Warm currents flood in, bump into the shelf and slope, and create eddies that are favorable for spawning. Unfortunately, this also happens to be an oil exploration and drilling hot spot -- Block recalls regularly spotting petroleum research vessels when conducting research in the area in the past.

Although Block won't estimate what the accident will do to bluefin population numbers, she hints that the effect on tuna and other marine species could be devastating.

"There is a much larger disaster unfolding here environmentally than people realize," she said. "There is a lot of focus on the Louisiana shoreline, but this is America's greatest fisheries nursery, and we've got to pay attention to what's going on immediately."
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