Fishermen in the small Japanese town of Taiji are set to begin their annual dolphin drive, capturing and killing hundreds of the animals in a government-sanctioned hunt.
The annual culling has sparked international outrage since its portrayal in the 2009 Oscar-winning documentary "The Cove."
Since then ardent animal rights activists, including an interviewee of the film, Ric O'Barry, have spoken out against the slaughter.
O'Barry attended this massacre on Monday in protest and was later arrested in the nearby town of Nachikatsuura for not carrying his passport.
The police said they were following up on a tip about a rental car being driven by a drunken driver. A breath test showed the activist was within the legal limit.
Despite the ongoing massacre, it's thought that the killing is on the decline and last year 800 were killed, compared to 2,000 the year before.
One reason for the decrease could be that some financial incentives are being curbed.
In May, the Japanese Association of Zoos and Aquariums agreed to stop sourcing dolphins from the Taiji hunt.
Previously businesses could pay up to $100,000 (£65,000) for each live animal.
Dominic Dyer, policy adviser at the Born Free Foundation, said in an interview:
"I have been able to tell the story of the greed and exploitation which fuels the trade in dolphins at Taiji Cove.
"The Japanese Government and fishing industry claim the slaughter of dolphins is all about culture when its really just about cruelty.
"A dead dolphin at Taji Cove is worth around £260 to the fishermen, most people in Japan do not eat dolphin meat as it contains dangerous levels of heavy metals in fact most of the dolphins killed end up as dog food or fertiliser."
Despite Japan moving forward in stopping sourcing the dolphins for entertainment, China, Russia and other nations could still pay top money for the marine mammals.
Conservationists have spoken out about the dangers of such killings and although the species of bottleneck dolphins are not currently endangered, they could be in danger in the future.
Randall Reeves, an expert with the International Union for the Conservation of Nature told NBC News:
"Dolphins and other toothed whales everywhere are already under threat from fishing nets, loss of habitat and prey, and climate change,
"So from the outset, they're just the wrong thing to hunt if you are going to hunt something to survive."
The killing season runs from September 1st until May next year.