Dose estimation to wild medaka around Fukushima Dai-ichi nuclear power plant

More than 10 y have passed since the Fukushima Dai-ichi Nuclear Power Plant (F1-NPP) accident, but there are still many areas with high levels of radioactive contamination, especially reservoirs and lakes, where the levels decrease slowly. The exposed dose to non-human biota is of great concern. In this work, the exposure dose to wild medaka (small aquarium fish) around F1-NPP was measured/estimated by two approaches: in situ measurement and with the ERICA assessment tool. S2 is a reservoir located 7.5 km from F1-NPP, and the ambient dose rate was 25.0 mu Sv per h in 2012, but decreased to 4.82 mu Sv per h in 2021. The external exposure dose rate to wild medaka living there was 0.8-11.8 mu Gy per h (2017-21) by in situ measurement, and the estimated dose rate with the ERICA assessment tool was 0.6-54.5 mu Gy per h (2012-21). The estimated and measured doses to wild medaka are not expected to cause any significant radiation effects.