Movement of a little radioactivity in migrating Bluefin tuna might be a first, but it is not a threat to food safety.  

Researchers from Stony Brook University’s School of Marine and Atmospheric Sciences and Stanford University’s Hopkins Marine Station claim to be the first scientists to document radioactive material in the sea being moved by biological migration.

It means that while air and water did not move radioactivity from Japan to California, it has arrived in the muscle of the big tuna.  Their study is published in the Proceedings of the National Academy of Science.


Bluefin tuna are believed to have passed through waters made radioactive by the earthquake and tsunami damaged Fukushima Daiichi nuclear power plant, on March 11, 2011, before migrating the Pacific Ocean to California in August 2011.

When the Bluefin arrived in California waters, the researchers said tests from 15 tuna samples showed elevated levels of radioactivity, but at amounts well within safety limits.  The two radioactive substances found were cesium-134 and cesium-137.

The Japanese plant damaged in the magnitude-9 earthquake is far from being the only nuclear hotspot created in the Pacific’s fishing waters.  For example:

– The French did not cease using the atolls of Mururoa and Fangataufa for nuclear tests until 1996.   Over 30 years, the French conducted 46 nuclear tests in the atmosphere and 147 underground.   

– U.S. nuclear tests in the Pacific’s Marshall Islands ended in 1963 after 220 megatons was exploded in 105 atmospheric tests.

Bluefin tuna arriving in California waters off San Diego tested for radioactivity were 20 times lower than safe levels and more than 30 times lower for naturally occurring gamma-emitting radioisotopes.

The researchers say the importance of the study is in using the radioactivity data to track migratory patterns of the Pacific Bluefin tuna and other species in the Pacific.   

The study will be repeated with large numbers of samples this summer.

Japan consumes about 80 percent of Atlantic and Pacific Bluefin tuna because its tender red meat is used in sushi.