High levels of contamination have been measured at the shoreline of the Fukushima Dai-ichi complex in recent days, prompting the government to set limits for the first time on the amount of radiation permitted in fish.
While officials have said the crack in a maintenance pit plugged early on Wednesday was the only one found, they have not explicitly ruled out that radioactive water is leaking into the sea from another point.
Authorities insisted the radioactive water would dissipate and posed no immediate threat to sea creatures or people who might eat them. Most experts agreed.
Still, Japanese officials adopted the new standards as a precaution. And the mere suggestion that seafood from the country that gave the world sushi could be at any risk stirred worries throughout the fishing industry.
"Even if the government says the fish is safe, people won't want to buy seafood from Fukushima," says Ichiro Yamagata, a fisherman who lived in the shadow of the power plant. "We probably can't fish there for several years."
Fukushima is not a major fishing region, and no fishing is allowed in the direct vicinity of the plant. But experts estimate the coastal areas hit by the massive wave last month account for about a fifth of Japan's annual catch.
Radiation concerns in the area intensified after the discovery over the weekend of the crack, which photos showed water pouring out of and splashing into the sea.
Since then, workers have raced to find a way to seal it, pouring in concrete and injecting a mixture of polymer, sawdust and shredded newspaper. Both failed.
But on Wednesday morning, Tokyo Electric Power Co. spokesman Naoki Tsunoda said the injection of 1500 litres of "water glass," or sodium silicate, and another agent near a seaside pit appeared to be successful.
It was a rare bit of good news for the utility that owns the crippled nuclear plant, located about 220km northeast of Tokyo. But highly contaminated water continues to pool around the complex. Tsunoda said officials were investigating whether the contaminated water is leaking from other places.
The new limits on radioactivity in fish were imposed after TEPCO announced water tested near the plant on Saturday contained levels of radioactive iodine 7.5 million times the legal limit. That level had dropped to 5 million two days later.
Japan said some fish caught last week about 80km from the plant would have exceeded the new safety limits, which may change as circumstances do.
Fears of radiation contamination prompted India to announce on Tuesday that it was halting food imports from Japan. Few countries have gone so far, but India's three-month ban reflected the unease created by the nuclear crisis among consumers. India said the ban would last three months or until the risk subsides. It planned to review the situation weekly.
Yamagata, whose home is within the 20km evacuation zone around the plant, is staying in a Tokyo football stadium with his wife and about 140 other refugees. He expects his fishing days are over.
After the magnitude-9.0 earthquake on March 11, he ran outside and watched the second floor of his house collapse, then fled with his family when tsunami warnings sounded.
Since then, he hasn't been allowed to return to check on the 5-tonne boat he used to troll for flounder. He assumes it's gone, too. The tsunami killed up to 25,000 people and left tens of thousands homeless as it swamped about 400km of the northeastern coast and knocked out power to the nuclear plant.
Workers there have been desperately trying to cool down overheated reactors, but the effort has required spraying large amounts of water and allowing it to gush out wherever it can escape, sometimes into the sea.
Radioactivity will continue spewing into the air and water until cooling systems are restored.
The radiation standards for fish will be the same as for vegetables. After spinach and milk exceeded safety limits following the quake, health experts said people would still have to eat enormous quantities of tainted produce or dairy before getting even the amount of radiation contained in a CT scan.
Japan imports far more fish than it exports, but it sent the world $US2.3 billion worth of seafood last year.
Some people were undaunted. At Sushizanmai, a sushi bar just outside Tokyo's famed Tsukiji fish market, customers were still eating Japan's famed raw fish delicacies on Tuesday night.
But chef Seiichiro Ogawa said the fuss over radiation could hurt business. His restaurant is trying to get more fish from the western part of Japan, which has not been affected by the nuclear crisis.
"Japanese customers are especially sensitive to this kind of thing, so I'm worried they'll stop eating sushi," said Ogawa, who has already seen his business drop 50 percent after foreigners stopped visiting the city after the quake. "We need this nuclear problem to be resolved."
TEPCO also said this week it is purposely dumping more than 3 million gallons of low-level radioactive water into the sea to make room in a storage tank for more highly contaminated water that it needs to remove before workers can restore important cooling systems.
That announcement angered Fukushima's federation of fisheries groups, which sent the company a letter of protest.
"Our prefecture's fisherman have lost their lives, fishing boats, piers and buildings due to the Great Eastern Japan Disaster," federation chairman Tetsu Nozaki said in the letter. "This low-level contaminated water has raised fears among fishermen that they will never be able to fish in our prefecture's waters again, and we absolutely want you to stop."
TEPCO's reputation has taken a serious hit in the crisis. On Tuesday, its stock dropped 80 yen - the maximum daily limit, or 18 percent - to just 362 yen, falling below its previous all-time closing low of 393 yen from December 1951. Since the quake, the share price has plunged 80 percent.
In what could be an effort to counter the bad publicity, Takashi Fujimoto, TEPCO's vice-president, said it was offering 20 million yen in "apology money" to each town or city affected by the mandatory evacuation zone around the plant.
That's likely to be little comfort to fisherman Yamagata and his wife, Chiharu, who are angry with TEPCO over the situation.
"All we heard was that the plants were safe, safe, safe," she said. "I feel like they were hiding things from us. Now that radiation is seeping out, it's too late."
Ichiro Yamagata, who is 50, said he would like to return to his home and his job, but he sees no way that could happen. Nearly 17,000 boats have already been reported damaged in three hardest-hit prefectures, and that's just a partial tally.
Some fishing boats that left the harbour immediately after the quake got far enough out to sea that they were safe from the tsunami, Yamagata said, but others were swept away.
For now, the Yamagatas are passing their days at the football stadium, sleeping on mats in large rooms sectioned off with blue, knee-high dividers. They have no possessions - Ichiro Yamagata doesn't even have his driver's licence - and only enough cash in the bank to last six months.
"After that, I'm going to have to find some kind of work," he said. "But fishermen can't be salarymen. I can only do simple jobs."
