Recent reports have exposed what some people had predicted at the time of the Fukushima nuclear disaster: that radiation would spread. And it has, through fish that migrates between North America and Japan.

Reuters recently reported that “low levels of radioactive cesium from Japan’s Fukushima Daiichi nuclear accident turned up in fish caught off California in 2011”. The statement was based on a recent report compiled by Stanford University’s Hopkins Marine Station.

Bluefin spawn off the Japanese coast and many migrate across the Pacific. The researchers analyzed tissue samples collected in August 2011, five months after the nuclear spill. All samples contained reactor byproducts cesium-134 and cesium-137 at levels that produced radiation about three percent higher than natural sources.

Most of the radiation leaked in April 2011. Radioactive cesium does not quickly sink to the sea bottom but remains dispersed in the water column, from the surface to the ocean floor. Fish can swim right through it and will ingest it through seawater or by eating contaminated organisms. Bluefin tuna typically have low levels of natural radiation such as potassium 40.

[Editors note: to put these figures and the relative risks they pose into context, visitors are encouraged to read this related article by TEC contributor Rod Adams as well as this article on the health risks from blue fin tuna at Deap Sea News.]