Scientists hope to test new samples of Pacific bluefin tuna after low levels of radioactive cesium from Japan's Fukushima Daiichi nuclear accident turned up in fish caught off California in 2011, researchers reported Monday.

The bluefin spawn off Japan, and many migrate across the Pacific Ocean. Tissue samples taken from 15 bluefin caught in August, five months after the meltdowns at Fukushima Daiichi, all contained reactor byproducts cesium-134 and cesium-137 at levels that produced radiation about 3% higher than natural background sources - but well below levels considered dangerous for human consumption, the researchers say.

Cesium-137 has a radioactive half-life of about 30 years, and traces of the isotope still persist from above-ground nuclear bomb tests in the 1950s and '60s. But cesium-134, which has a half-life of only two years, "is inarguably from Fukushima Daiichi," Stanford University marine ecologist Dan Madigan told CNN.

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