The anti-whaling group Sea Shepherd said the decision probably means the end of the hunt for the current season, the Australian Broadcasting Corp. reported. The Institute for Cetacean Research said the whaling fleet needs to refuel.
"Not this season, the season is over in 18 days," Paul Watson, the founder of Sea Shepherd, said. "They couldn't go up north and refuel again. It's all over and done with I think for this year. I don't think they have killed more than a dozen whales in total, we don't know for sure, but they couldn't have killed more than that."
Sea Shepherd said two of its boats were rammed Wednesday in Australian Antarctic waters by a Japanese fishing vessel and concussion grenades were thrown at its activists.
Commercial whaling has been banned since 1986. The Japanese whalers take advantage of an International Whaling Commission rule that allows whales to be killed for scientific research with the meat then sold commercially.
In 2010, a Sea Shepherd vessel, the Ady Gil, was sunk in a confrontation with the Japanese fleet.
In Australia, the federal environment minister, Tony Burke, said he was trying to confirm reports of attacks on Sea Shepherd vessels. Greg Hunt, the environment spokesman for the opposition, urged the government to send a customs ship to the area immediately.
"Failure to do so is simply a failure to acknowledge the conflict, the hostility, and the taking of whales in Australian waters," he said.