Radioactive bluefin tuna crossed the Pacific to US

May 28, 2012 ALICIA CHANG , AP Science Writer
This March 5, 2007 file photo shows workers harvesting bluefin tuna from Maricultura's tuna pens near Ensenada, Mexico. New research found increased levels of radiation in Pacific bluefin tuna caught off the coast of Southern California. Scientists said the radiation found in the fish came from Japan's Fukushima nuclear plant that was crippled by the 2011 earthquake and tsunami. (AP Photo/Chris Park, File)

Across the vast Pacific, the mighty bluefin tuna carried radioactive contamination that leaked from Japan's crippled nuclear plant to the shores of the United States 6,000 miles away - the first time a huge migrating fish has been shown to carry radioactivity such a distance.

"We were frankly kind of startled," said Nicholas Fisher, one of the researchers reporting the findings online Monday in the .

The levels of radioactive cesium were 10 times higher than the amount measured in off the California coast in previous years. But even so, that's still far below safe-to-eat limits set by the U.S. and Japanese governments.

Previously, smaller fish and plankton were found with elevated levels of radiation in Japanese waters after a magnitude-9 earthquake in March 2011 triggered a tsunami that badly damaged the Fukushima Dai-ichi reactors.

But scientists did not expect the to linger in huge fish that sail the world because such fish can metabolize and shed .

One of the largest and speediest fish, Pacific bluefin tuna can grow to 10 feet and weigh more than 1,000 pounds. They spawn off the Japan coast and swim east at breakneck speed to school in waters off California and the tip of Baja California, Mexico.

Five months after the Fukushima disaster, Fisher of Stony Brook University in New York and a team decided to test Pacific bluefin that were caught off the coast of San Diego. To their surprise, tissue samples from all 15 tuna captured contained levels of two radioactive substances - ceisum-134 and cesium-137 - that were higher than in previous catches.

To rule out the possibility that the radiation was carried by or deposited in the sea through the atmosphere, the team also analyzed , found in the eastern Pacific, and bluefin that migrated to Southern California before the . They found no trace of cesium-134 and only background levels of cesium-137 left over from nuclear weapons testing in the 1960s.

The results "are unequivocal. was the source," said Ken Buesseler of the Woods Hole Oceanographic Institution, who had no role in the research.

Bluefin tuna absorbed from swimming in contaminated waters and feeding on contaminated prey such as krill and squid, the scientists said. As the predators made the journey east, they shed some of the radiation through metabolism and as they grew larger. Even so, they weren't able to completely flush out all the contamination from their system.

"That's a big ocean. To swim across it and still retain these radionuclides is pretty amazing," Fisher said.

Pacific bluefin tuna are prized in Japan where a thin slice of the tender red meat prepared as sushi can fetch $24 per piece at top Tokyo restaurants. Japanese consume 80 percent of the world's Pacific and Atlantic bluefin tuna.

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.

Now that scientists know that bluefin tuna can transport radiation, they also want to track the movements of other migratory species including sea turtles, sharks and seabirds.

Explore further: Bluefin tuna catches to be reduced in Pacific: reports

More information: “Pacific bluefin tuna transport Fukushima-derived radionuclides from Japan to California,” by Daniel J. Madigan, Zofia Baumann, and Nicholas S. Fisher , PNAS, 2012.


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1.8 / 5 (5) May 28, 2012
VD, you realize that above ground nuclear testing occurred for several decades?

That said, it would be interesting to see how these recently irradiated fish compare with fish irradiated in the 40s, 50s and 60s.

I wonder. Are you still susceptible to penicillin? Or are you a hardened strain?
3 / 5 (2) May 29, 2012

What the world needs is another 200,000 nuclear reactors so that the economy can be entirely powered with nuclear power.

That would solve some major problems actually.
1 / 5 (2) May 29, 2012
Vendicar will call you on is matter. Shootist, can't forget him.
5 / 5 (3) May 29, 2012
They seem to have already forgotten the lessons of the Three Mile Island accident, where they found Cs in the river water BUT upstream from their reactor site. Turned out to be hospital waste, from 20 miles further up the river, NOT from the accident.
So this tuna Cs has a Rising Sun stamped on it? Tell me more.
1.3 / 5 (3) May 29, 2012
Oh the irrational fears of radiation. I wonder how many people will disregard the fact that its a very small amount of radiation and is safe to eat?
2 / 5 (5) May 29, 2012
Oh the irrational fears of radiation. I wonder how many people will disregard the fact that its a very small amount of radiation and is safe to eat?

you eat it and give it to eat to your kids and family.
3.7 / 5 (3) May 29, 2012
That would solve some major problems actually.

Yes. After we all glow in the dark we could reduce our lighting bills.
I wonder how many people will disregard the fact that its a very small amount of radiation and is safe to eat?

Radiation and its detrimental effects are a probabilistic thing and there is no 'safe to eat' level.
There is only a level below which you cannot discern cancer caused by source X and that caused by natural radiation with any certainty.

But as you say: It is sensible to have these thresholds so that people don't overreact.

Point being: this shows that radaition accidents (and nuclear testing) aren't confined/confineable to the locale where they happen - contrary to all other types of power generation (even oil slicks from burst supertankers are sort of local by comparison)
1 / 5 (3) May 29, 2012
the problem with these fish and radiation detection in general is that our instruments are SO sensitive that we can pick up radiation amounts that are nowhere near dangerous. Yet since it's there at all, people get all scared-monkey and start throwing shit everywhere.
2.8 / 5 (5) May 29, 2012
Radiation and its detrimental effects are a probabilistic thing and there is no 'safe to eat' level.

Sure there is, everything has radioactivity to greater or lesser amounts.

Those Cesium isotopes are extremely rare to begin with. So 10 times the "normal level" might sound scary, but 10 times almost nothing equals almost nothing. Note how they don't mention what normal levels are and what is considered safe. My little eye spies fear mongering.
5 / 5 (2) May 29, 2012
Sure there is, everything has radioactivity to greater or lesser amounts.

Maybe I didn't make myself clear: even the normal amount of radiation you are exposed to in your environment can cause cancer. It is merely a probabilistic chance that a radiation event will just so happen to interact with the telomeres of the DNA in one of your cells and turn that cell cancerous.

This happens all the time (and the body is pretty good at getting rid of these cells almost all of the time. About 100 such cells a day IIRC.) It's still a gamble when one of these cells will not be gotten rid off and will be in a position to proliferate and cause serious trouble. Such a chance would ONLY be zero if there was no background radiation at all (aside from chemical mutagens, of course)
5 / 5 (2) May 29, 2012
It's also a matter where that stuff gets absorbed in your body. some potentially radioactive stuff doesn'tget absorbed and you excrete it. This means the danger only persist while it is in your intestinal tract AND it just so happens to decay at within that timeframe.

Radioactive Iodine, for example, gets absorbed by the thyroid gland. So it stays until it decays (not a problem here. Radioactive Iodine has a half life of 8 days so any released at Fukushima should be almost completely gone by now)

Radioactive Strontium is chemically very similar to calcium so gets deposited in the bones (until it decays). Not good.

Radioactive Caesium is similar to Potassium and gets resorbed and deposited in muscle tissue.

10 times the "normal level" might sound scary, but 10 times almost nothing equals almost nothing

In nuclear waste disposal dumping stuff into the oceans is not considered acceptable. It tends to accumulate.
1 / 5 (2) May 29, 2012
Honestly, a single sunburn is likely more damaging to your DNA than eating an entire one of these tuna.
3 / 5 (4) May 29, 2012
This may be a side note, but it's important to point out that when the bluefin is sliced and presented raw, it is sashimi, not sushi. Sushi is the seasoned vinegared rice and inherently contains no fish, raw or cooked.
5 / 5 (3) May 29, 2012
Honestly, a single sunburn is likely more damaging to your DNA than eating an entire one of these tuna.
Probably. Though the two are notreally comparable. Caesium produces beta radiation upon decay. Sunburn is the result of gamma radiation.

Thing is we shouldn't shrug this off as just another of these things that happen and get dumped into the biosphere as if "the planet will just deal with it" - and we will carry on polluting like there is no tomorrow.

There is going to be a tomorrow. And if we keep on being willfully naive about the ramifications of our energy production schemes then at some point it won't look pretty.
1 / 5 (1) Jun 02, 2012
Swam the Pacific! I figured they chartered a boat.

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