No one was injured in the clash Saturday, which each side blamed on the other.
The U.S.-based activist group Sea Shepherd, which sends vessels to confront the Japanese fleet each year, accused the Japanese ship of deliberately rammed the Bob Barker — named after the U.S. game show host who donated millions of dollars for the anti-whaling group to buy it.
But Japan's Fisheries Agency said the activist boat caused the collision by suddenly approaching the harpoon vessel No. 3 Yushin Maru to throw bottles containing bad-smelling butyric acid at the Japanese ship.
The agency accused Sea Shepherd of "an act of sabotage" on the Japanese expedition, noting that it is allowed under world whaling regulations as a scientific expedition. Conservationists call the annual hunt a cover for commercial whaling.
Neither side's account could be verified. Video shot from the Bob Barker and released by Sea Shepherd shows the two ships side by side moving quickly through the water. The ships come closer together and the Japanese ship then appears to turn away, but its stern swings sharply toward the Bob Barker. The collision is obscured by spray, but a loud clanging noise can be heard before the vessels separate.
Sea Shepherd founder Paul Watson said a 3-foot-long, 4-inch-wide (1-meter-long, 10-centimeter-wide) hole was torn in the Bob Barker's hull, but it was above the water line and was not a threat to the ship. The Japanese agency said Yushin Maru sustained minor damage to its handrail and hull.
Bob Barker, famous for hosting "The Price is Right" for more than 30 years, said he had spoken to Watson about the collision and was happy to continue supporting the Sea Shepherd leader.
"I hope he is able to bankrupt them," Barker told The Associated Press. "He wants to sink this Japanese whaling ship economically. He wants to make it so they can't afford to continue to business. I'm all too happy to be able to support him."
Saturday's collision was the second this year between a Sea Shepherd boat and the Japanese fleet.