The Sea Shepherd Conservation Society, an anti-whaling group which is prone to using direct-action tactics to stop illegal whaling, was pursuing a Japanese fleet hunting whales for so-called "scientific purposes". The same fleet was involved in the incident in January, when the Sea Shepherd vessel, the Ady Gil, was sunk after a collision with another ship.
This time, the Bob Barker, so named after its celebrity benefactor, was pursuing the Japanese fleet and attempting to disrupt their whaling activities by blocking harpoon ships from reaching a factory ship where whales are butchered, when it collided with a harpoon ship.
"The harpoon ships started circling like sharks," the founder of Sea Shepherd, Paul Watson, told the Associated Press.
"They were making near passes to the stern and the bow of the Bob Barker, then the Yushin Maru 3 intentionally rammed the Bob Barker."
For their part, the Japanese whalers allege that the collision was caused by the Bob Barker, when it came too close in an attempt to pelt rancid butter at the crew of the harpoon ship.
Neither vessel was seriously damaged in the collision. Watson reported that welders are currently working on a gash in the side of the Bob Barker, and it will be ready to resume pursuit of the whaling fleet.
Japanese whaling operations are controversial - they appear to be legal under international conventions if they are truly done for scientific purposes, but groups such as the Sea Shepherd Conservation Society allege that this is a front for commercial whaling. Negotiations
on the future of these operations are under way within the International Whaling Commission, and it appears the Japanese whaling may be legitimised, albeit with a quota cut.
In the meantime, an international scientific expedition
has been dispatched to these same waters, in an attempt to prove that lethal methods are not necessary to study whales. The effort is an explicit challenge to Japan's assertions that its whaling is scientifically necessary. An array of nations are backing the study.
"We remain absolutely and completely opposed to killing whales in the name of science," said Australian Conservation Minister Peter Garrett, whose government is one of the Southern Ocean Research Partnership's supporters.