Japanese whalers pursuing minke whales in waters south of Australia are themselves being hunted, with Sea Shepherd's new ship trying to find them amidst fog in the Australian Whale Sanctuary, north of Antarctica.
The crew on Sea Shepherd's newly-minted anti-whaling ship, the Ocean Warrior, reported seeing a harpoon boat hunting minke whales this morning.
The charity's other vessel, the Steve Irwin, which was also searching in the area a few hundred kilometres north of Casey Station, will now join the Ocean Warrior and attempt to stay in contact with the whaling fleet.
Ocean Warrior captain Adam Meyerson told the ABC heavy fog was making it difficult to track the Japanese whalers.
"We're really wanting to find the mother ship, the slaughter house, the floating processing plant, where they butcher all the whales," he said.
"When you find that, you can track down the harpoon ships."
Captain Meyerson said the speed of the Ocean Warrior enabled then to keep pace with the whaler.
"We actually out-ran them this morning," he said.
The Ocean Warrior is equipped with a water cannon, which will be used alongside the usual tactic of getting between the harpoon boats and the whales.
Last year Japan's Institute for Cetacean Research (ICR) confirmed it killed more than 300 minke whales in its 2015 expedition.
But Captain Meyerson said only a few of the prized whales had been spotted.
"We haven't seen any evidence of any whaling yet, there's quite a few whales down here, but not too many minke whales," he said.
"We've seen a lot of humpbacks and a lot of sperm whales."
Japanese shirk fine, whaling goes on
Japan suspended its annual whale hunt in 2014 after the International Court of Justice found its whaling program, known as JARPA II, was not based in science and was therefore illegal.
Japan then designed a new whaling program, called NEWREP-A, which it submitted in November 2014 to the International Whaling Committee (IWC) for assessment.
The new research plan intended for fewer whales to be killed, but for the hunt to be carried out over a wider area.
The IWC found there was insufficient justification for killing whales in the name of science under the new program.
Japan's whaling activities continue despite continued pressure from environmental groups.
The killing of whales and dolphins within the Australian Whale Sanctuary is prohibited by the Federal Government.
In 2015 Australia's Federal Court fined Japanese whalers Kyodo $1 million for hunting whales within an Australian sanctuary. The fine has not been paid.
The Federal Government has repeatedly condemned Japan's whaling activities but has resisted calls to send a government vessel to intervene.
International law professor and whaling expert Tim Stephens said Australia could put a stop to the practice by taking Japan to the International Tribunal for the Law of the Sea.
He said it could be argued Japan is not meeting its international obligations to sustainably protect whales.
"The tribunal has a system of mandatory dispute settlement, that's very difficult to opt out of," Professor Stephens said.
"That's why it does remain an option for Australian or another government to take a case against Japan.
"And there's really very little Japan could do about it."
Environment Minister Josh Frydenberg and the ICR have been contacted for comment.