One by one they are unloaded, weighed and tipped into plastic vats of ice – hundreds of octopuses that flail and whip the melting ice into a foaming mollusk soup.

In this state they look far from appetising, but the catch marks a critical step forward in the battle to save the local fishing industry almost a year and a half after the meltdown at nearby Fukushima Daiichi nuclear power plant.

“That’s quite a good catch,” said Kasunori Endo, general manager of the Soma-Futaba fisheries co-operative.

Endo was hopeful that consumers would quickly grow accustomed to seeing even more Fukushima seafood reappear on supermarket shelves: “I’m looking forward to increasing the number of species we can catch. We may soon be able to fish for crab and squid. We won’t make serious progress until we bring in a bigger, more varied catch.”

The nuclear disaster heaped an extra layer of misery on the region’s fishermen, who already had to contend with the destruction of fishing boats, equipment and ports by the tsunami that roared ashore on 11 March last year.

Fishing co-operatives in Fukushima prefecture voluntarily refrained from venturing into local waters – an official ban on catching most marine species was imposed only recently – amid fears that radioactive leaks from the plant had made seafood too dangerous to consume.

Then, 15 months after the start of the nuclear crisis, boats in Soma, which is about 30 miles north of the plant, were given permission on a trial basis to start catching two types of octopus and whelks, selected because they are thought to trap fewer radioactive particles than other species.

After the catch was unloaded, samples were taken to a nearby lab, to which the Guardian was granted rare access. Staff dressed in white overalls, masks, hats and gloves sliced octopus tentacles into chunks, then wrapped them in plastic to be taken into an adjoining room for testing.

On this occasion, as on every other day since fishing in Soma resumed at the end of June, the two radiation-measuring devices in the lab revealed not even the slightest trace of radioactive iodine-131, and caesium-134 and -137. In March, the government introduced stricter acceptable radiation levels in seafood, increased from 500 becquerels per kilo to 100 becquerels.

“There may be very tiny amounts, but they are so small they don’t even register on equipment as sophisticated as this,” says Noriaki Haga, the fisheries official in charge of testing. The octopuses are tested again after they have been boiled, in preparation for sale.

Despite proof that this particular delicacy is safe, Fukushima’s fishermen concede that the consumers they once depended on to make a living have yet to be convinced.

2012 Guardian News and Media Limited