http://news.yahoo.com/s/ap/20100215/ap_on_re_as/as_antarctica_whaling By TANALEE SMITH, Associated Press Writer Tanalee Smith, Associated Press Writer 1 hr 46 mins ago ADELAIDE, Australia An anti-whaling activist was being held in custody on board a Japanese whaling vessel Tuesday after secretly boarding it the day before, the whalers said. Peter Bethune scaled the Shonan Maru 2 early Monday with the goal of making a citizen's arrest of the ship's captain and handing over a $3 million bill for the destruction of a protest ship last month. Japan's Institute of Cetacean Research, which sponsors the whale hunt, said the boat's captain had advised Bethune "that in line with the Japanese Mariners Act he was taking necessary measures and restrained Mr. Bethune." The statement said Bethune used a knife to cut the vessel's protection net to enable his boarding. "At that time, Mr. Bethune cut his left thumb and has since received medical treatment from the Japanese crew," the institute said in a statement. It said Bethune told them he had thrown the knife into the sea after boarding the ship. The statement did not say what would be done with Bethune. The Japanese say his boarding was illegal. The brazen move was another escalation by the U.S.-based Sea Shepherd activist group meant to hamper the whaling activities of the Japanese. The Sea Shepherd said Bethune approached the Shonan Maru 2 by Jet Ski and jumped onto the netting to board the vessel early Monday. His goal was to demand the cost of replacing the Ady Gil, an activist ship he captained that was destroyed in a collision with a whaling ship last month. He also wanted the Shonan Maru 2 captain to surrender to Sea Shepherd, or take his ship to the nearest Australian or New Zealand port to turn himself in to authorities for the Ady Gil's destruction and the attempted murder of six Ady Gil crew members. On Monday, Tetsuro Fukuyama, Japan's state secretary for foreign affairs, called the incident "regretful." "We yet have not clarified his (the intruder's) intention," Fukuyama said. "Once we confirm the fact and nationality of the ship he belongs to, we would post strong protest and urge them to take an appropriate action." 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 sheared off the protest boat's nose and caused it 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.