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Fish near Fukushima plant still showing radioactivity

TOKYO — Elevated levels of cesium still detected in fish off the Fukushima coast of Japan suggest that radioactive particles from last year’s nuclear disaster have accumulated on the seafloor and could contaminate sea life for decades, according to new research.

The findings published in Friday’s issue of the journal Science highlight the challenges facing Japan as it seeks to protect its food supply and rebuild the local fisheries industry.

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More than 18 months after the nuclear disaster, Japan still has bans on the sale of 36 species of fish caught off Fukushima, rendering the bulk of its fishing boats idle and denying the region one of its mainstay industries.

Still, some local fishermen are trying to return to work. Since July, a handful of them have resumed small-scale commercial fishing for species, like octopus, that have cleared government radiation tests.

Radiation readings in waters off Fukushima and beyond have returned to near-normal levels.

But about 40 percent of fish caught off Fukushima and tested by the government still have too much cesium to be safe to eat under regulatory limits set by the Japanese government last year, said the article’s author, Ken O. Buesseler, a leading marine chemistry specialist at the Woods Hole Oceanographic Institution, who analyzed test results from the 12 months after the March 2011 disaster.

Because cesium tends not to stay in the tissues of saltwater fish very long, and because high radiation levels have been detected — particularly in bottom-feeding fish — it is likely that fish are being newly contaminated by cesium on the seabed, Buesseler wrote in the Science article.

‘‘The fact that many fish are just as contaminated today with cesium 134 and cesium 137 as they were more than one year ago implies that cesium is still being released into the food chain,’’ Buesseler wrote.

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