Key Points:

The Sea Shepherd Conservation Society has given up its pursuit of the Japanese whaling fleet in Antarctic waters after becoming concerned that it is being hunted by a ship that plans to seize its vessel and video footage.

Sea Shepherd boss Paul Watson said yesterday he had been told the Japanese Government had sent a security vessel, the Taiyo Maru No38, from Fiji to intercept his anti-whaling ship, Steve Irwin.

The crew was believed to have orders to seize the Steve Irwin and video footage it had taken of the whalers, he said.

"The ship is expected to arrive in the Ross Sea within days. We cannot allow this documentation to be captured by Japan," Mr Watson told The Dominion Post.

The Steve Irwin had only enough fuel to pursue the whalers for four more days so Mr Watson decided to retreat to Australia rather than risk having his boat boarded.

Confrontations between the Steve Irwin and the whaling fleet had resulted in two collisions in the past few days, causing minor damage to both parties' vessels.

Mr Watson said he was concerned there would be serious injuries if his ship remained on the whaling fleet's tail.

"Another four days is simply not worth getting someone killed."

He said his crew had done everything possible to hinder Japan's whaling and would return next season with a bigger and faster boat.