Radioactive Tuna From Japan Caught Off California Coast

PACIFIC GROVE, Calif.U.S. scientists have discovered Pacific bluefin tuna with levels of radioactive cesium 10 times higher than the amount measured in tuna off the California coast in previous years. The findings suggest the radioactive tuna migrated from Japan, where radioactive cesium and iodine spewed into the sea after the Fukushima Daiichi nuclear plant was crippled by a massive earthquake and tsunami March 11, 2011.

According to the study published in the journal Proceedings of the National Academy of Sciences, scientists at the Hopkins Marine Station and Stony Brook University said they have unequivocal evidence that Pacific bluefin tuna, Thunnus orientalis, transported Fukushima-derived radionuclides across the entire North Pacific Ocean.

In August 2011, the scientists tested Pacific bluefin caught by sport fishermen off the coast of San Diego. Tissue samples from all 15 tuna caught contained levels of two radioactive substancesceisum-134 and cesium-137that were higher than in previous catches. The levels of radioactive cesium were 10 times higher than the amount measured in tuna off the California coast in previous years, but far below safe levels set by the U.S. and Japanese governments.

The findings indicate that Pacific bluefin tuna can rapidly transport radionuclides from a point source in Japan to distant ecoregions and demonstrate the importance of migratory animals as transport vectors of radionuclides. Other large, highly migratory marine animals make extensive use of waters around Japan, and these animals may also be transport vectors of Fukushima-derived radionuclides to distant regions of the North and South Pacific Oceans.