Pacific bluefin tuna carried radioactivity from Japan’s 2011 Fukushima Daiichi nuclear disaster all the way across the ocean to the shores of California, scientists reported Monday.
They didn’t bring much — the levels were far lower than, for instance, levels of naturally occurring potassium 40 that have existed in the ocean for centuries — but the radioactivity was enough to survive the fishes’ migration east to North America from the Western Pacific, which they undertake when they’re around a year old, said doctoral student Daniel Madigan, who studies the migration patterns of tuna at Stanford University.
Last year's March 11 quake and tsunami set off meltdowns at the Fukushima Daiichi nuclear power plant.
“We showed that a bluefin tuna is capable of picking up radioactive material and transporting it across the ocean. That’s new. Traditionally people don’t think of migratory animals as transport vectors for radioactive materials,” he said.
Madigan made the discovery in samples of fish he collected during the summer of 2011, about five months after the disaster, when “Fukushima was on everyone’s mind.” Not sure what he’d find, he collected bits of Pacific bluefin tuna flesh from the catches of fishermen in San Diego and sent 15 samples from smaller fish (which, being younger, would have been the most recent migrants from Japan) to Nicholas Fisher’s laboratory at Stony Brook Universityin New York. There they were analyzed for the presence of radioactivity from Fukushima.