This paper focuses on an overview of radioactive cesium 137 (quasi-Cs137 included
Cs134) contamination of freshwater fish in Fukushima and eastern Japan based on the
data published by the Fisheries Agency of the Japanese Government in 2011. In the
area north and west of the Fukushima Nuclear plant, freshwater fish have been highly
contaminated. For example, the mean of active cesium (quasi-Cs137) contamination of
Ayu (Plecoglossus altivelis) is 2,657 Bq/kg at Mano River, 20–40 km north-west from the plant. Bioaccumulation
is observed in the Agano river basin in Aizu sub-region, 70–150 km west from the plant.
The active cesium (quasi-Cs137) contamination of carnivorous Salmondae is around 2 times
higher than herbivorous Ayu. The extent of active cesium (quasi-Cs137) contamination
of Ayu is observed in the entire eastern Japan. The some level of the contamination
is recognized even in Shizuoka prefecture, 400 km south-west from the plant.