TAIJI, Japan — Taiji reveals its Janus face as soon as you emerge from the road tunnel on the town's periphery. Bottlenoses leap out of the water in unison at the aqua park, where visitors are invited to board rowing boats and "play with the dolphins." Giant models of two whales, framed by a brilliant blue sky, serve as reminders of the town's traditions, while the emerald waters of the Pacific Ocean combine with heavily wooded cliffs to form a coastline of outstanding beauty.

But for all its natural charms, this town of 3,500 people is inextricably linked with something much less palatable: the systematic slaughter of thousands of dolphins for their meat.

After years of operating with near-impunity, Taiji's hunters are the reluctant subjects of a new U.S. documentary that has sparked an international campaign to end the carnage in this isolated, picturesque corner of western Japan.

Over the course of three years and at a cost of $2.5 million, the makers of "The Cove" used a panoply of hi-tech equipment, including underwater cameras, hidden microphones and aerial drones, to capture graphic images of the dolphins' bloody demise.

The film, directed by the National Geographic photographer Louie Psihoyos, won the audience award at this year's Sundance Film Festival and has received positive reviews in the U.S., Europe and Australia since its release at the end of July.

Last week, the organizers of the Tokyo International Film Festival caved in to pressure and agreed to screen the film next month, although it is unlikely to go on general release in Japanese cinemas.

Its hero is Ric O'Barry, a former dolphin trainer for the 1960s TV show Flipper, who has conducted a 15-year crusade to put an end to the slaughter in Taiji. "I've been working with dolphins for most of my life," he said. "I watched them give birth. I've nursed them back to health. When I see what happens in this cove in Taiji, I want to do something about it."

He has witnessed fishermen pursuing pods of dolphins across open seas, banging metal poles together beneath the water to scare their prey and disrupt their sonar.

The animals are herded into a large cove, where they are kept overnight before being dragged into a neighboring inlet to be slaughtered, out of sight, as the shallow water turns a deep shade of red. "It is Dante's Inferno for dolphins," O'Barry said.

Though local officials deny they are succumbing to international outrage, the film appears to be having an impact.

In the first hunt of the season earlier this month, Taiji's fishermen rounded up 100 bottlenose dolphins and 50 pilot whales, which, despite their name, are the largest members of the dolphin family. Then something unusual happened. The pilot whales were killed, but 30 bottlenoses were sold to aquariums and the remaining 70 set free.

Taiji's 26 dolphin hunters — a fraction of the town's 500 fishermen — and their supporters say the culls are necessary to protect squid and fish stocks from ravenous cetaceans. And why, they ask, would they abandon a tradition stretching back 400 years because of outside interference?

"Westerners slaughter cattle and other animals in the most inhumane ways imaginable, but no one says a word," said one Taiji resident. "Why is it that only Japan gets this kind of treatment?"

Over the next six months the town's fishermen will catch about 2,300 of Japan's annual quota of 20,000 dolphins. While the meat from a single animal fetches a modest $500, aquariums and sea parks are prepared to pay $150,000 for a live specimen.

There is some truth to claims among Taiji residents that they have been unfairly singled out. Of the 13,067 dolphins caught in Japan in 2007, only 1,623 came from Wakayama prefecture, where the town is located. Hunters in Iwate prefecture were much busier, killing more than 10,000 dolphins, according to the Fisheries Research Agency. But as the birthplace of Japan's whaling industry and the only place where dolphins are still harpooned close to the shore, Taiji is an obvious target for protesters. Coastal whaling began here in the early 1600s but fell victim to the 1986 global ban on commercial whaling, which does not cover dolphins.

The barbaric nature of their deaths aside, bottlenose dolphins and pilot whales contain dangerously high levels of mercury, with one study showing that mercury levels among Taiji residents are about 10 times higher than the national average.

Locals reject the idea that they are slowly poisoning themselves. "I have been eating whale and dolphin for years and I'm perfectly healthy," said a 75-year-old Taiji fisherman. "The people around here live well into old age."

O'Barry's aim is to pressure Taiji's hunters into maintaining their recent "non-slaughter" policy and eventually to persuade the Japanese government to ban the culls for good amid an "international tsunami of attention."

"Stopping the slaughter and sale of dolphins would be a major victory for the people of Japan who risk eating mercury-laced dolphin meat," he said.

"The Cove" has got his campaign off to a promising start.