For centuries the people of the small Japanese town of Taiji have herded dolphins into a cove and slaughtered them for their meat.
The annual drive begins every September. This year, however, bowing to international pressure following the recent release of a critically acclaimed documentary, the townspeople are backing off from the hunt and releasing many of the dolphins that in years past would have been killed.
Villagers insist that some dolphins have been released in the past and this release is not a result of the movie.
The villagers say the hunt is a tradition, that the dolphins are used for food, and that culling the population is essential to their livelihoods as fishermen in these already overfished waters.
Dolphin drive hunting is not against the law. The Japanese government allows for 20,000 dolphins a year to be killed.
But images from the documentary "The Cove" show some of the dolphins being picked out and sold to aquariums, while many others, left starving and stranded for days, are brutally killed with spears.
"It's a brutal and arcane practice. I'm also appalled that any aquarium would take from the drive," said Diana Reiss, director of Marine Mammal Research at the National Aquarium.
The annual hunt lasts seven months. Over that time, thousands of dolphins are driven by fisherman into the cove, the outlet of which is then closed off by nets.
"The Cove" depicts an inlet turned red with the blood of dolphins, and injured animals are seen gasping for life among other dead and dying animals.
"You could see [a dolphin] trying to get away and it was swimming straight for us to shore, and it actually made it through a couple of the nets, and every time it came up for a breath you could see all this blood coming up," said one eye witness interviewed in the film.
The film, released earlier this year, showed a spotlight on Taiji, bringing international interest and condemnation on the small town in Wakayama Prefecture on the Pacific Ocean.
Hayden Panettierre, an actor and activist, who was in "The Cove" and has worked on behalf of the animal rights group Save the Whales Again!, called the slaughter "brutal and horrific" in an interview on "Good Morning America."
The film, Panettierre said, shows "how much impact it has on our world that we slaughter these innocent and beautiful creatures that are really huge in our circle of life."
Locals, however, insist the hunt is a critical part of their economy and their culture.
"The fishermen who do this here will tell you, 'This is our tradition. This is our culture. You don't understand us. You eat cows, we eat dolphins,'" said Ric O'Barry, star of "The Cove," and the former trainer of dolphins for the television show "Flipper."
O'Barry surreptitiously filmed the movie over several months in 2007, sometimes disguising cameras as rocks.
ABC News recently visited Taiji and witnessed fisherman releasing dolphins from the cove back into the open ocean, likely a result of the international attention.
Panettierre said the fishermen's willingness to release some dolphins was a good start, but international pressure needs to continue.
"They're supposed to set about 50 bottlenose dolphins free after selling about 50 for around $150,000 each to wildlife-marine parks," she said. "I think it is a step and we should not overlook it but at the same time there's a lot that needs to be done."