Militant activists Wednesday hurled stink bombs at Japanese whaling ships after finally catching up with the fleet, blaming "spy planes" for disrupting their Antarctic harassment campaign.
The Japanese harpoon vessel Shonan Maru No 2 (R) attacking the Sea Shepherd vessel Steve Irwin (L) with water canons in the Southern Ocean off Antarctica December 22.
Anti-whalers threw rancid butter-filled Christmas tree baubles "like baseballs" at the Japanese ships to make their decks too foul to work, spokesman Paul Watson told AFP.
"They can't work on the deck with these stinkbombs and it makes life very unpleasant on board," he said. "In East Africa they shoot elephant poachers, down here we just throw stinkbombs."
Watson said the Sea Shepherd activists latched on to the Japanese ships just before dawn, about a month after setting out from Australia on their annual bid to stop the slaughter of hundreds of minke and fin whales.
He accused the Japanese of chartering planes from Australia to pinpoint his Steve Irwin vessel and of sending a pursuing ship, sparking a chase among icebergs which set back their campaign by weeks.
"We didn't think anything of it at the time, we thought they were Australian government planes, routine," he said.
"And then about six hours later the Shonan Maru was on our tail so we figured out that the planes had given the location so that the Japanese could tail us."
He said he only shook off the ship -- after skirmishes involving water cannon, a laser-type device and a military-style sonar weapon -- when he returned to port and then left under low cloud cover, making air surveillance impossible.
"I think spent about 20,000 dollars on that search, about 12 hours in total, and they didn't find us and we were able to slip past," Watson said.
Watson said the super-fast Ady Gil powerboat, newly commissioned this year, and the Bob Barker, another ship being used for the first time, were now pursuing the whalers in Antarctica's Commonwealth Bay.
"There's a whole pursuit down there along the ice edge," Watson said. "They're not killing any whales today, they're running from us," he added.
Sea Shepherd activists have harassed the Japanese fleet over the past six hunting seasons and claim to have saved the lives of hundreds of whales.
An international moratorium on commercial whaling was imposed in 1986 but Japan kills hundreds each year using a loophole that allows "lethal research" on the animals.
Japan makes no secret of the fact that whale meat ends up on dinner tables, and accuses Western nations of not respecting its culture.