Pacific Bluefin Tuna Show Signs Of Fukushima Radiation

Pacific Bluefin tuna caught off the coast of California in 2011 show levels of radioactive contamination that can only be traced to the nuclear accident at Fukushima.

The fish are still within safe levels to eat, and even below radiation from other isotopes that occur naturally in the environment such as potassium-40.

The Bluefin tuna were found to have higher levels of caesium-137 and caesium-134. Caesium-137 may be linked to the atomic fallout from weapons testing in seawater; however caesium-134 may not. Caesium-134 has an incredibly short half-life of two years, and the only incident to explain its presence is the accident at Fukushima.

The fish were caught in August, 2011 off the coast of San Diego. The parents of these fish would have spent one to two years off the coast of Japan before heading to the eastern Pacific to their feeding grounds.

"It's a lesson to us in how interconnected eco-regions can be, even when they may be separated by thousands of miles," Nicholas Fisher, a professor of marine sciences at Stony Brook University, New York, said to BBC News.

The researchers also examined Yellowfin tuna, which spends its time in the eastern Pacific and not near Japan. These fish showed no difference before or after Fukushima.