Mr O'Barry, 75, was taken into custody Monday (August 31), on the eve of Taiji kicking off its controversial six-month dolphin hunt, for allegedly failing to carry his passport after being stopped by police.
“He was released at 8:40pm on Tuesday,” a local police spokesman told AFP.
“He admitted to not carrying his passport – there was no need to keep him in custody.”
He will likely face a fine of up to 100,000 yen (B29,638), but the arrest of a foreigner in Japan for not carrying a passport is rare. Police said they had initially questioned Mr OʼBarry on suspicion of drunk driving.
Mr OʼBarry, who appeared in the Oscar-winning documentary “The Cove” which drew worldwide attention to the small town of Taiji, has frequently visited the community to protest against its dolphin hunt.
Police have dispatched more officers to the town for the hunt in anticipation of possible clashes between locals and activists.
Immigration authorities have denied entry to anti-whaling demonstrators at airports, according to conservation group Sea Shepherd.
In the annual catch, people from the southwestern town corral hundreds of dolphins into a secluded bay and butcher them, a scene thrust into the global spotlight in “The Cove”.
Environmental campaigners visit the town every year now to watch the hunt.
The latest dolphin-killing hunt, which opens on September 1 every year, has been pushed back due to bad weather, a local fisheries association official said.
Mr OʼBarry, who found fame first in the 1960s for catching and training five dolphins for the well-known TV series “Flipper”, has recently fought against keeping the mammals in captivity.