LOS ANGELES (AP) - Researchers are surprised to find radiation levels this high in the bluefin tuna that are turning up along the California coast -- 10 times higher than the amount usually found in those fish.

They've carried the radioactive contamination 6,000 miles from the waters near Japan's crippled nuclear plant -- the first time a huge migrating fish has been shown to carry radioactivity that far.

But the levels are still well within the safe-to-eat limits.

The researchers report their findings in the Proceedings of the National Academy of Sciences.

Previously, smaller fish and plankton were found with elevated levels of radiation in Japanese waters after the magnitude-9 quake in March of last year triggered a tsunami that badly damaged nuclear reactors.

But scientists didn't expect the fallout to linger in huge fish that sail the world, because those fish can metabolize and shed radioactive substances.