Inside Japan's battle to prove fish is safe after Fukushimanuclear disaster

Packed in iced refrigerator boxes, fresh fish is express-mailed to the Onjuku lab by prefecturalgovernments and fishing cooperatives across eastern Japan. By day's end, each specimen will bephotographed and tagged with details about where and when it was caught; processed, packed intoplastic vessels, and placed for one hour in a $200,000 germanium semiconductor detector to test forthe presence of radioactive isotopes iodine, Cesium-137 and 134.

Workers prepare fish samples for radiation testing at the Marine Ecology Research Institute inOnjuku, Japan.

Under unusually conservative radiation safety limits enacted in the wake of the Fukushima accidentin March 2011, a reading of more than 100 bequerels per kilogram triggers an automatic ban.

The pattern of ocean dilution is in line with trends seen right after the 1986 Chernobyl accident,when cesium levels spiked, but then dissipated within months, the agency says.

 Amassing the results of tens of thousands of samples like this, Japan's Fisheries Agency says oceanand fish contamination has sharply declined since the March 2011 nuclear accident at theFukushima Daiichi nuclear plant. In the three months following the catastrophe, 53 percent of fishsampled off Fukushima showed radiation levels surpassing the safety limit of 100 bequerels perkilogram. By the following year, the proportion of contaminated fish had halved. And by Novemberof this year, only 2.2 percent of samples tested unsafe. (Away from hard-hit Fukushima, the ratio isless than one percent.)

Onjuku is better known for surfing than food safety, perhaps because the quasi-governmentalMarine Ecology Research Institute operates out of a drab row of whitewashed buildings nestled inhills overlooking the Pacific. MERI is among dozens of labs set up since the mid-1970s -- at the dawnof Japan's nuclear power boom. As reactors were built along Japan's coastline, the labs weredelegated to certify that fish supplies remain safe despite wastewater discharge from the nuclearplants.

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MERI screens 200 species every year, including shellfish and seaweed, as well as the more commoncod and salmon, from waters as deep as 1,300 feet. Seawater and sediment are also monitored, asare freshwater fish.

Fish caught off Japan's coast wait to be prepared for radiation testing at the Marine EcologyResearch Institute in Onjuku, Japan. CBS

"It takes an hour to run a test," Atsushi Suginaka, director of the fisheries processing industries andmarketing division of Japan's Fisheries Agency told CBS News. Unlike rice or other farm products,"fish are internally contaminated, so it's time-consuming to check."

Most problematic have been ground-feeding species like flounder,greenling and cod, perhaps because of their exposure to "hotspots" of cesium on the sea floor, says Buesseler.

The minced fish then goes to the lab. A veteran researcher,Nobuhiro Nonaka, picks up a baggie of Pacific cod and carefullyempties the slurry into a plastic beaker, which will be shielded inmore bagging to prevent any stray radiation leaking.

"Sometimes we are tempted to take a bite," one employee tells us, adding that he resists the urge.

Strontium testing is done at a separate facility; it takes one month to scan a single sample.

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Fishermen were not allowed to fish for a year after the devastating 2011 earthquake. In late July,they learned the Fukushima nuclear plant was l...

A sample of ground fish is seen inside a germanium semiconductor detector, which will test the fishfor radioactive isotopes, at the Marine Ecology Research Institute in Onjuku, Japan.

Closing in on the three-year anniversary of the catastrophe, Fukushima's scenic 100-mile coastlineremains closed, except for small-scale trial fishing. According to statistics from Fukushimaprefecture, in 2010, the last year before the catastrophe, Fukushima harvested 38,657,050 tons ofseafood, worth about $106 million.

But winning back once-lucrative food export markets in Asia, where bans on Japanese food remain inplace, won't be easy. All of Japan's nuclear plants have been closed down while the cleanup atFukushima continues. That cleanup is slated to stretch over decades, but even with all the plantsswitched off, labs like one at Onjuku are sure to stay busy.

Shedding the tarnish of radiation contamination is a priority not just for Fukushima, of course, butalso for Prime Minister Shinzo Abe, who aims to double Japan's meager farm, fish and forestryexports by 2020 to $9.7 billion per year. Long protected by subsidies and import barriers,Japanese farmers and fishermen are infamously inefficient. As Japan's domestic market shrinks,Tokyo is anxious to make the nation's food producers as globally focused and competitive as theircolleagues in the auto industry.

Ken Buesseler, a scientist at the Woods Hole Oceanographic Institution in Massachusetts who hasstudied marine contamination, wrote in the magazine Science that tightening safety standards "mayhave had the opposite effect, as the public now sees more products considered unfit for humanconsumption."

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This fish isn't destined for a fancy restaurant or a supermarket, and it won't likely ever land onanyone's dinner plate. Instead, the seafood samples will be checked for radiation -- part of Japan'sfight to restore confidence in its food supply after the Fukushima nuclear disaster.

 Onjuku is an old fishing port and a guide likes to point out that the locals are more adept athandling fish than researchers -- so it's locals who work in the prep area. Clad in disposable aprons,retired fishermen and housewives photograph, measure and weigh each sample before getting downto business. Like practiced restaurant hands, they quickly trim away heads, fins, organs, skin andbones; only edible portions are checked for radiation. The relatively appetizing-looking fillets arethen ground into unappetizing minced fish and packed in baggies.

Species that have remained radiation-free even around Fukushima -- where commercial fishing isstill on hold in the wake of the accident -- include mollusks, squid and octopus, "species that don'thave backbones tend to accumulate less radioactive substances," explained Suginaka, of theFisheries Agency.

By comparison, the U.S. tolerates much higher amounts of radiation; 1,200 bequerels per kilogram,and critics have argued that Japan's safety standard -- created to reassure terrified citizens after the

catastrophe -- is unnecessarily low.

"The most important thing is not to contaminate the work area," explains Nonaka. The sample isplaced inside the germanium detector, a device the size of a hotel room safe, and an hour later,the results flash up on a display.

Radioactive leak impedes Japanese fishing, again

After delivery each morning, specimens head first to a tiny room off the main lab to be prepared fortesting.

ONJUKU, Japan -- Every morning, hundreds of pounds of fresh fish, hauled in from ports acrosseastern Japan, is rushed to this sleepy town hours away from the capital.Â

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A team of experts from the International Atomic Energy Agency (IAEA) recently backed Japan'sclaim that radiation levels, despite ongoing problems with wastewater leaks at the crippled nuclearplant, were returning to normal.