Persistently high radioactivity in some fish caught close to the Fukushima nuclear plant has sparked a government investigation into the physiological basis for contamination and why radiation readings in some specimens remain hundreds of times over the official safe limit.
The Council for Science and Technology Policy, a government panel, is to study caught fish in order to calculate when they became contaminated—and where.
Since the Fukushima No. 1 nuclear power plant disaster in March 2011, the Fisheries Agency has measured the radiation levels of about 20,000 fish. The overall trend has been a decline in detected amounts of radioactive cesium.
However, in August, two greenlings caught 20 kilometers north of the Fukushima plant were found to have cesium levels of 25,800 becquerels per kilogram, the highest level ever measured in fish since the nuclear accident. The government standard for food is 100 becquerels per kilogram.
And in March, tests recorded a level of 18,700 becquerels per kilogram in freshwater salmon in the Niidagawa river near Iitate, a village northwest of the nuclear plant.
Furthermore, the concentration of cesium in freshwater salmon and char caught since March has not been decreasing, leading to restrictions on the shipment of such fish from Fukushima Prefecture and surrounding areas....