(Cormorant fishing, it should be noted, is a textbook illustration of Japan's (and Asia's) traditionally manipulative relationship with nature: Hungry birds are trained to dive for fish with leashes tightened around their necks, preventing them from swallowing their catch.)
The ayu population is not in danger, authorities claim, because fish ladders will be built into the estuary barrier and an artificial breeding program will supply plentiful stocks.
But the Construction Ministry's own data suggests otherwise. When a similar estuary barrier was built on the neighboring Kiso River, the \o7 ayu \f7 catch was nearly halved--from 152,000 pounds when construction began in 1979, to 77,000 pounds in 1988, the latest year for which figures are available.
"If these fish ladders worked so well, then why are they paying billions of yen to compensate fishery unions for their losses?" asked Yasuji Yasufuku, 75, an avid amateur fisherman in Gujo Hachiman, a picturesque mountain village on the upper reaches of the Nagara.
"Already we've lost much of our \o7 ayu \f7 run," lamented Yasufuku, who makes his living carving folk Buddhist statues. "I started fishing with my father when I was 9, and the river was teeming with fish. All you needed was a bamboo pole to stick in the water and you could catch 30 \o7 ayu \f7 a day. It's not like that now."
The government has paid undisclosed amounts of money, estimated to be in the tens of millions of dollars, since the plan was first approved in 1968, buying off the rights of commercial and amateur fishing associations along the river.
The green light to begin construction three years ago followed a sudden breakthrough in negotiations with \o7 shijimi \f7 clam fishermen in Ise Bay, whose catch would be devastated by the change in the way fresh water mixes with salt water below the estuary barrier.
\o7 Satsuki masu, \f7 a rare species of trout, are another \o7 cause celebre \f7 for opponents of the dam, who say the fish is found only in the Nagara River. The Construction Ministry disputes that, saying the fish is simply known by another name in nearby rivers.
"It's a question of what is natural anymore," said Masanori Shinagawa, a local Construction Ministry official overseeing the construction. "The Nagara River is almost totally man-made at this point. The river has adapted to something like a natural ecosystem, but you can't say it's anything special or near a natural state."
Local residents have largely remained silent on the dam, reflecting a cultural tendency to eschew controversial issues--or perhaps they are displaying a collective fear of floods, from which the project is supposed to protect them.
Megumi Omori, a homemaker turned firebrand protester, is the exception in Nagashima.
"A lot of people around here are afraid to speak out because of bad memories of the flooding," Omori said. "I'm a newcomer and I don't really know the terror of the Ise Bay typhoon, but my neighbors tell me I've got a lot of courage to move to such a dangerous place."
She and her husband bought a plot here 15 years ago from developers selling off swampy farmland to cater to a booming population in the Nagoya area. Omori was uninterested in the dam construction until one day, in the summer of 1989, she was riding her small motorbike across the Nagara and saw that workers had torn up a section of marsh where she enjoyed watching birds.
"That wonderful marsh was suddenly in ruins, and it had this horrible stench," she said. "All the living things in the marsh had been dredged up and they were rotting. The nests were gone, and the birds were flying around in confusion."
Omori became a zealot and started a band of Nagashima residents to fight the dam. So far she has recruited five people, all newcomers.
Japanese from distant places have had better luck organizing. Spearheading the anti-dam movement has been a charismatic sports fishing journalist from Osaka, Reiko Amano. She enlisted such celebrities as the late Ken Kaiko, a prominent man of letters and fishing enthusiast, and orchestrated the colorful flotillas of protesting boats to entice television news cameras.
Her group also has lobbied fairly successfully in the murky political world, where power and wealth are traditionally gained by promoting public works projects, not trying to stop them. Yet the activists persuaded several members of Parliament to call for a halt in construction pending a new environmental impact assessment.
So far, that remains an elusive goal. Kazuo Aichi, the present Environmental Agency chief whose predecessor had spoken out against the Nagara River dam, has declared Japan's environmental activists "ideologically strange."
"I don't know why there's such a fuss over the Nagara River. It seems to have become a symbol of something," said Aichi, who has a reputation as an "internationalist" in Japan's stodgy ruling party.