(Update) The albacore tested after Fukushima had 340 – 1024 millibequerels/kg of combined cesium, according to Simplyinfo.org. 0.34 to 1.024 becquerels/kg. One-tenth of the bluefin tuna that the Stanford researchers tested.
(H/T anon reader)
The Seattle Times article below doesn't report the number. It doesn't mention cesium-137 (half-life 30 years) either, which should have been detected alongside cesium-134 if it was of the Fukushima origin.
To avoid "baseless rumor", I suppose. But I still wish the reporter (or the researchers and government officials speaking to him) simply mentioned the number, instead of doing the "Edano" and saying "It's barely detectable, no effect on health, it's just so little ..."
The article says "it is allowing scientists to track the migratory patterns of tuna for the first time", which I take it to mean "the first time in Washington and Oregon". The researchers at Stanford University in California already announced the result of their study of bluefin tuna off southern California in May this year.
From The Seattle Times (10/27/2012; emphasis is mine):
Trace Fukushima radiation found in Northwest albacore tuna
Researchers have found tiny amounts of radioactive cesium in albacore caught off Washington and Oregon. The radiation, originating from the 2011 tsunami in Japan, is thought to pose no public-health risk, but it is allowing scientists to track the migratory patterns of tuna for the first time.
Since the early 1950s, scientists have argued about one of the West Coast's most popular fish — albacore tuna.
Are the silvery streaks that tempt thousands of anglers each year part of one family of highly migratory fish? Or are there really two groups of speedy tuna, each traveling a different route around the sea?
Now this half-century-old argument could be clarified by a disturbing new pollutant: radioactive isotopes from Tokyo's Fukushima Daiichi nuclear power plant.
Oregon State University researchers and federal scientists are finding exceedingly tiny amounts of radioactive cesium in albacore caught off the coast of Washington and Oregon. And it's clear the radionuclide originated with the nuclear accident that followed the deadly tsunami that hit Japan in March 2011.
While some forms of cesium persist in the environment for decades, one isotope scientists saw, cesium-134, has a half-life of a little more than two years and could only have come from that accident.
So far, the trace amounts that OSU scientists found in tuna are far less than anything that would pose a risk to humans; a fish eater would have to consume several thousand pounds of the most radioactive albacore they discovered just to increase by 1 percent the amount of radiation they're exposed to from everyday sources.
"The amounts they found were incredibly small," said Donn Moyer, spokesman for the Washington state Department of Health, which also tested the same samples and came up with the same results. "There's nothing really remarkable about the amounts."
But because cesium decays so quickly, the discovery makes clear that fish caught in Northwest waters picked up the radiation while feeding on smaller fish in or around Japan.
"We're talking about barely, barely detectable levels," said Jason Phillips, who led the work while a graduate student at OSU's College of Earth, Ocean, and Atmospheric Sciences. "But because the radiation has to be derived from Fukushima, they had to pick it up within its vicinity or in the drift."
For most of the 1950s, researchers tagged North Pacific albacore and determined that the fish along the West Coast traveled between here, Japan and California and Mexico.
But in the 1970s researchers began to see signs that suggested some of the California fish might be part of a different population.
"It turns out there may be two different populations," said Richard Brodeur, with the National Marine Fisheries Service. "Ours up here might be completely different from those down off of California."
But the fast travel so far and fast — between 50 and 200 miles in a day — that tracking their movements is almost impossible, and no one has been able to confirm their theory.
After the Fukushima disaster, Phillips and Brodeur and another graduate student in radiation health had an idea: Why not map migration routes for West Coast tuna using the radioactive fish?
So far they've tested 18 Northwest fish, and the results are consistent: Fish caught before the tsunami are radiation free; fish caught afterward contain trace amounts of cesium.
But the real test is yet to come. The scientists have been collecting dozens of albacore from fishermen off the California coast. They plan to test those fish soon. If those don't show the same traces of cesium-134, it would suggest that they didn't travel to the same place as the Northwest fish.
Understanding when and where albacore travel can help scientists protect stocks of a West Coast fish worth tens of millions of dollars annually.
The researchers are presenting their findings to a conference in Italy this weekend.
The Stanford researchers found 4 Bq/kg of cesium-134 (and 6.3 Bq/kg of cesium-137) in bluefin tuna off California, which do migrate. Yellowfin tuna don't, and I'm not aware of any testing or study of the radiation in yellowfin tuna.
Oregon State University's press release on October 24, 2012 is more detailed, but still no number mentioned. The press release does say the researcher detected cesium-137 also, and the fish they tested were caught last year and frozen:
The researchers first identified two Fukushima-linked isotopes – Cesium-137 (Cs-137) and Cesium-134 (Cs-134) – this July, in samples of fish caught and frozen in 2011.
In the OSU press release, the researcher Delvan Neville says they tested about 70 pounds (about 32 kilograms) of tuna, or 18 samples:
“This is what we've seen after testing about 70 pounds of tuna,” Neville said. “When you've run one or two samples, you can't really say much about the population you're testing yet. When you've run five or six, you could make some guesses. When you're up to, at this time, 18 samples and everything has fallen fairly neatly into two groups of results, you can start to make some predictions about that population.