For the first time, scientists have discovered that tuna contaminated by last year's radiation leak from the crippled Fukushima nuclear plant have crossed the Pacific Ocean into U.S. waters, according to the Associated Press. Scientists have been startled to discover the radioactive fish some 6,000 miles from their place of origin, the first time that large, migrating fish have been shown to carry contaminants over such a great distance.

Normally, radiation and other contaminants are found in smaller fish and plankton, and only in waters close to the source of contamination. However, levels of radioactive cesium have been found at ten times the normal levels in fish off of the coast of California. The current levels, say officials, are still below the levels considered unsafe by the U.S. and Japanese governments.

In March of 2011, a massive earthquake and devastating tsunami struck northeastern Japan, killing thousands and reducing entire towns to mud and rubble. The Fukushima nuclear plant was caught unprepared for the disaster, and subsequently multiple reactors at the plant melted down, spewing radioactive materials into the air and water and triggering mass evacuations.

Bluefin tuna are large, fast-swimming fish, growing up to ten feet in length and weighing up to half a ton. The fish swim at "breakneck" speeds and cross the oceans to feed and mate.

Scientists tested tuna from other regions to discover if the cesium-134 and cesium-137 found in the fish might have come from somewhere else, or if the fish had ingested plankton from water affected by the radiation leak.

Ken Woeller of the Woods Hole National Oceanographic Institute is an outside researcher who was consulted by the investigation. He said the results "are unequivocal. Fukushima was the source."

(image via WikiMedia Commons)