As Reuters points out: ” Unlike some other compounds, radioactive cesium does not quickly sink to the sea bottom but remains dispersed in the water column, from the surface to the ocean floor. Fish can swim right through it, ingesting it through their gills, by taking in seawater or by eating organisms.. “

As CNN notes: ” Neither (of the scientists who tested the fish) thought they were likely to find cesium at all, they said. And since the fish tested were born about a year before the disaster, “This year’s fish are going to be really interesting,” Madigan said.

“There were fish born around the time of the accident, and those are the ones showing up in California right now,” he said. “Those have been, for the most part, swimming around in those contaminated waters their whole lives.”

In other words, the 15 fish tested were only exposed to radiation for a short time. But Bluefin arriving in California now will have been exposed to the Fukushima radiation for much longer.

--Below comments from me--

Can't link the article - It's a US Veteran publication if you want to google.