photo by tomosuke214 (Flickr CC)
Pacific bluefin tuna have been clocked swimming at speeds of 48km/h (30mph). This might help explain why bluefin carrying low levels of radiation believed to be from Fukushima were found off the coast of California so soon after the nuclear disaster in Japan.
Though the reports are only surfacing now, 15 radioactive tuna were caught off of San Diego in August 2011, only around 4 months after the majority of radiation was released into the waters around Fukushima.
The elevated levels of cesium-134 and cesium-137 found in the tuna are considered safe and are well below the Japanese and US safety standards limits, even though they are 10 times the cesium levels measured in tuna off the California coast in previous years.
From Reuters:
Because cesium 134 is generated only by human activities – nuclear power plants and weapons – and there was none in the Pacific for several years before the Fukushima accident, they reckoned that any cesium 134 they found in tuna off California had to come from Fukushima.
Yellowfin tuna from the eastern Pacific were also analyzed for comparison and were found to contain no increased levels of radiation. However, there is still background radiation left over from nuclear tests carried out in the 1960s. Don’t you just love what the US government did in the name of security?
This is the first time a large migrating fish has been found to carry radioactivity over such a large distance – 9,650km or 6,000mi. Scientists did not expect the radioactive to remain in large fish like tuna, believing that the fish would metabolize and discharge substances.
And of course it’s not over yet…
From AP:
The real test of how radioactivity affects tuna populations comes this summer when researchers planned to repeat the study with a larger number of samples. Bluefin tuna that journeyed last year were exposed to radiation for about a month. The upcoming travelers have been swimming in radioactive waters for a longer period. How this will affect concentrations of contamination remains to be seen.
See this video report from the Guardian for more:
