Japan's Fisheries Research Agency said Friday the fish was one of 37 black sea bream caught in the area as part of an effort to determine how much nuclear contamination has entered the food chain after the power plant suffered a meltdown in 2011 after a powerful earthquake and tsunami.
The black sea bream caught had a stunning 12,400 becquerels per kilogram of radioactive cesium in its body, which is 124 times the amount considered safe for human consumption.
Two other fish caught also tested beyond the safe amount, at 426 and 197 becquerels per kilogram. The remainder of the fish were within safe limits, the Asahi Shimbun reported.
Black sea bream are restricted from being caught in the area after the Fukushima disaster and have not been circulated for food in Japanese fish markets, officials said.