Sea Shepherd activist Erwin Vermeulen has been released from a Japanese prison.

The Dutch environmentalist was arrested last December while he was respresenting Sea Shepherd as a ‘cove guardian’ in Taiji during the annual dolphin drives. Vermeulen was allegedly involved in a pushing incident while trying to photograph the dolphins.

The public prosecutor has appealed the court’s verdict, which freed Vermeulen and ordered him to pay a fine of some 1,000 euros. Pending the decision of an appeals court, the Dutchman is not allowed to leave Japan.

Sea Shepherd is considering launching proceedings against the Japanese state for holding Vermeulen for two months in a case which is minor enough to warrant a small fine – should that also be the outcome of the appeals court.

The bloodiness of the dolphin drives around the village of Taiji was first highlighted by Sea Shepherd in 2003. Since then, the organization has appointed ‘cove guardians’ to monitor the hunters’ activities.

US judge denies preliminary injunction to whalers

In a separate court case in the US on Thursday, a judge refused to restrain the US Sea Shepherd group from disrupting the activities of Japanese whalers, allegedly with violence.

Japanese whalers sought a court order preventing the Sea Shepherd and its founder Paul Watson "from engaging in physical attacks on plaintiffs' vessels in the Southern Ocean," referring to the ocean encircling Antarctica.

Last month Japan's Fisheries Agency said anti-whaling activists threw paint and foul smelling acid at a

whaling ship in the Antarctic ocean in a fresh bid to halt the annual hunt, officials said.

Two boats belonging to Sea Shepherd approached the Japanese whaling vessel Yushin Maru No. 2 YS2  - which was seen leaving the Japanese port of Shimonoseki for the annual hunt - and launched 40 bottles containing paint and butyric acid, the agency said.

The fisheries agency’s mission is officially said to be for "scientific research," with the fleet aiming to catch around 900 minke and fin whales, according to a plan submitted by the government to the International Whaling Commission.