The World Trade Organization has ruled in favor of South Korea, allowing its ban of Japanese seafood:
Hirobumi Ohinata (2019, April 12). WTO panel lets Seoul maintain seafood ban over Fukushima fears THE ASAHI SHIMBUNhttp://www.asahi.com/ajw/articles/AJ201904120045.html
A World Trade Organization appeals panel sided with South Korea’s continued ban on Japanese seafood following the Fukushima nuclear disaster, shocking officials in Tokyo seeking to end such “discrimination” against Japanese products.
The panel accepted Seoul’s argument that peculiar circumstances surrounding Japanese products after the 2011 triple meltdown at the Fukushima No. 1 nuclear power plant allowed the South Korean government to set stricter import restrictions.
Not too long ago the Japan Times reported cesium levels detected in Japanese fish:
Radioactive cesium above legal limit detected in fish caught off Fukushima
https://www.japantimes.co.jp/news/2019/02/02/national/science-health/limit-cesium-detected-fish-caught-off-fukushima/#.XFm3RWl7ncc
FUKUSHIMA - Radioactive cesium exceeding the state limit has been detected in fish caught off Fukushima Prefecture for the first time in about four years, the prefecture’s fisheries cooperatives association has said. The cesium level of 161 becquerels per kilogram, exceeding the limit of 100, was detected in a skate, a type of ray, caught at a depth of 62 meters during test fishing Thursday.
No doubt Fukushima isn't the only place with contaminated fish given decades of atmospheric tests and deliberate dumping of radioactive waste into the ocean.
Jacob Hamblin's Poison in the Well provides a very thorough and fascinating history but doesn't cover the contemporary era where Fukushima dominates as the worst nuclear disaster for the world's oceans.
FUKUSHIMA DAIICHI APRIL 15, 2019 (Precipitation is 90% and humidity 80%):