A Japanese court on Wednesday ruled that a Dutch supporter of militant environmentalist group Sea Shepherd was not guilty of assaulting a man in the dolphin-hunting town of Taiji.

Erwin Vermeulen, 42, was indicted for allegedly punching the man in December when he was stopped from entering an off-limits area near a secluded bay where large dolphin hunts take place.

Judge Satoshi Shibayama at the Wakayama district court said testimony given by the alleged victim was not sufficient to convict Vermeulen, Jiji Press reported.

"The testimony by the victim is inconsistent," said the judge, noting that the Japanese man's account of having been pushed with the defendant's left hand conflicted with the fact that Vermeulen held a radio in his right hand and a camera in his left, Jiji said.

The picturesque town in western Japan came to global attention after "The Cove", a hard-hitting film about the annual hunts, won an Academy Award for best documentary in 2010.

Every year the fishermen of Taiji corral some 2,000 dolphins into a secluded bay, select a few dozen for sale to aquariums and marine parks, and stab the rest to death for meat in a slaughter that turns the water red.

The town's fishermen defend the hunt as a cultural tradition and "The Cove" was met by protests from right-wing activists when it was screened in Japan.