Pete Bethune boarded the Shonan Maru 2 in an act that New Zealand's prime minister called dangerous. The protest was another escalation by the U.S.-based Sea Shepherd activist group meant to hamper the whaling activities of the Japanese.
Bethune planned to hand over a bill for $3 million, the cost of replacing the Ady Gil, an activist ship he captained that was destroyed in a collision last month. He also wanted to make a citizen's arrest of the captain of the Shonan Maru 2 for the Ady Gil's destruction and the attempted murder of the six Ady Gil crew members, according to a Sea Shepherd statement.
Sea Shepherd founder Paul Watson said Bethune had boarded the Japanese whaling fleet security ship and will demand that the Shonan Maru 2 captain surrender to Sea Shepherd or take his ship to the nearest Australian or New Zealand port to turn himself in to authorities.
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But Japan's Institute of Cetacean Research, which sponsors the whale hunt, called the boarding a "publicity stunt" and said it is the Sea Shepherd activist who will be held accountable. In a statement, the institute said the Japanese whalers did not have a means to return Bethune to his ship.
"What he (Bethune) has just done is an illegal act" under maritime law, institute spokesman Glenn Inwood told The Associated Press. "Worst case scenario, he will be taken back to Japan."
However, Donald Rothwell, a professor of international and maritime law at the Australian National University, said Bethune's boarding was not illegal under international law unless he planned to do harm to the crew or imperil the safety of the Shonan Maru 2. Merely making a demand or presenting a letter and a bill did not constitute terrorism or piracy.
Takashi Mori, an official in charge of whaling at Japan's Fisheries Agency, said it was still trying to determine an appropriate response.
Japan has a six-vessel whaling fleet in Antarctic waters as part of its scientific whaling program, an allowed exception to the International Whaling Commission's 1986 ban on commercial whaling. It hunts hundreds of mostly minke whales, which are not an endangered species. Whale meat not used for study is sold for consumption in Japan, which critics say is the real reason for the hunts.
The Sea Shepherd sends vessels to confront the Japanese whaling fleet each year, trying to block the whalers from firing harpoons and dangling ropes in the water to try to snarl the Japanese ships' propellers.
The whalers have responded by firing water cannons and sonar devices meant to disorient the activists. Collisions have occurred occasionally, including the Jan. 6 collision between the Sea Shepherd's high-tech speedboat Ady Gil and the Shonan Maru 2 that caused the Ady Gil to sink. There were only minor injuries.
The governments of Australia and New Zealand, which have responsibility for maritime rescue in the area where the whale hunt is usually conducted, have repeatedly urged both sides to tone it down.
On Monday, New Zealand Prime Minister John Key called the latest Antarctic activities "downright dangerous."
"These people are operating in Antarctica, where if you land in the water and (remain) there for more than about 12 minutes, you'll be dead. I don't really think its terribly sensible, that kind of behavior," Key said.