Some Bluefin tuna showing up off the Pacific Coast of the U.S. are contaminated with radiation from Japan’s damaged nuclear reactor, according to breaking news releases.
This is the first time such large migrating fish have been shown to contain radioactivity over such a long distance, said The Associated Press (AP). The 6,000-mile distance between the United States and the tsunami-damaged Fukushima Daiichi nuclear plant still poses a threat. The plant, built by General Electric, was damaged by a massive earthquake and tsunami that hit Japan on March 11.
“We were frankly kind of startled,” Nicholas Fisher, one of the researchers reporting the findings online Monday in the Proceedings of the National Academy of Sciences, told the AP. Radioactive cesium levels were 10 times higher than what was detected in tuna off the California coast in prior years. U.S. and Japanese governments say that the levels are below their safe-to-eat limits.
Smaller fish and plankton were found with elevated levels of radiation in Japanese waters after the magnitude-9 earthquake and the resulting tsunami; however, scientists never expected such high findings in the large fish that migrate worldwide because the bluefin metabolize and shed radioactive substances, the AP explained. Bluefin are one of the world’s largest and fastest fish, growing to 10 feet in length and weighing over 1,000 pounds. The fish spawn off of Japan’s coast, swimming to California and Mexico.
Fisher of New York’s Stony Brook University, and a team, tested Pacific bluefin caught off the coast of San Diego following the accident and found that tissue samples from all 15 tuna captured contained levels of two radioactive substances—ceisum-134 and cesium-137—at levels greater than previously seen, said the AP. The team also analyzed yellowfin tuna to rule out other radiation and concluded that Bluefin absorbed radioactive cesium from swimming in contaminated waters and feeding on contaminated prey, including krill and squid, the scientists told the AP.
The fish would typically shed the radiation metabolically with growth, but were unable to flush all the toxins, the AP explained. “That’s a big ocean. To swim across it and still retain these radionuclides is pretty amazing,” Fisher said, wrote the AP. Researchers will be repeating the test this summer with a larger sampling and should include tuna that were exposed to the radiation for about one month. The scientists also hope to track other migrating species, such as sea turtles, sharks, and seabirds.