Bluefin Tuna (Thunnus thynnus) harvest in the Pacific Ocean.
Earlier this week, Californian scientists discovered that prized bluefin tuna caught off the shores of San Diego had radioactive cesium at levels 10 times higher than in previous years (although still safe to eat based on U.S. guidelines). The bluefin — which spawn off the Japanese coast and then swim thousands of miles east, to waters off California and Mexico, to school — likely absorbed the radioactivity by eating smaller sea creatures that had been affected by fallout from Japan’s stricken Fukushima Daiichi nuclear reactor. The tuna can grow to be as much as 10 feet long and weigh 1,000 pounds each. Studies of both Yellowfin and Bluefin tuna from before the Fukushima nuclear spill showed they lacked the same elevated radioactive levels as ones that arrived in U.S waters during the tsunami’s aftermath. This is the first time a migrating fish has been known to carry radioactivity this far.
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