The full impact on fish species is still not clear but one reading suggested radioactive iodine levels in seawater 127 times the permitted level.

Already one South Korean retailer has stopped selling Japanese fish because of customer concerns.

North Asia correspondent Mark Willacy reports from Tokyo.

(Sound of auctioneer at Tsukiji market)

MARK WILLACY: It's the biggest fish market in the world but business is on the slide at Tokyo's Tsukiji market.

Turnover is 30 per cent down on this time last year with the market receiving less tuna, mackerel and other fish because none is being caught by fishing communities obliterated by the tsunami.

All along the coast fishing communities are in ruins. All they can do now is salvage what they can.

After the disaster I travelled through these communities all along the tsunami zone from Asahi in the south to Hachinohe in the north - a distance of about 600 kilometres.

I saw fishing boats including massive trawlers picked up by the tsunami and deposited on docks, on streets and through houses. Sometimes they were tossed hundreds of metres inland.

Takahagi is one such community where the fishing industry is now a pile of debris.

(Sound of Toshiichi Tayama speaking)

"We don't know where the boxes to store the fish have disappeared to," says fisherman Toshiichi Tayama. "We don't know where the baskets have gone either," he says.

The tsunami - 14 metres high in some parts - smashed boats, obliterated warehouses and wharfs and tangled hundreds of thousands of nets.

One city saw its fish market sink 10 centimetres into the sodden earth.

But the big worry now is what's seeping from the Fukushima nuclear plant.

High radiation levels have been found in the Pacific Ocean off the plant site.

In fact elevated amounts of five kinds of radioactive material have been detected including iodine-131 which was discovered to be nearly 127 times the allowed level.

(Sound of Toshiichi Tayama speaking)

"As for resuming fishing, radiation is something that's harmful to human beings so we have to be careful," says fisherman Toshiichi Tayama. "So when we finally go fishing again we have to be cautious," he says.

One bright spot: iodine-131 has a short half-life meaning its radioactivity decreases rapidly.

(Sound of the sea)

For generations these Japanese communities have made a proud living from the sea - the same sea that rose up and tore them and their populations to shreds.

This is Mark Willacy reporting for AM.

www.abc.net.au/am/content/2011/s3172169.htm

March 24, 2011