The two men taken hostage had boarded the Yushin Maru (pictured doing its dirty work here) to deliver a message to the Japanese captain that the whalers were in violation of international conservation law by targeting endangered species in an established whale sanctuary in violation of a global moratorium on commercial whaling. They also notified the captain that Australia had just passed a court ruling barring Japanese whalers from the Australian Antarctic Economic Exclusion Zone.
Greenpeace says it is following another vessel in the same fleet, the Nisshin Maru, in its vessel the Esperanza.
Captain Paul Watson of the Sea Shepherd's ship the Steve Irwin says he believes the men are being treated well.
"I had initial concerns but I think there's too many people watching the situation for them to be mistreated now," he said.
The entire whaling fleet is on the run. According to the Sea Shepherd no whales have been able to be slaughtered for the last four days and it does not look as if the whaling operations are going to begin again for another week at least, and not at all if the vessels are prevented from regrouping. Crew members from the Sea Shepherd ship 'Steve Irwin' point out they have a "good supply of fuel and can remain in the area for some time and will continue to police the illegal whaling operations by the Japanese fleet".
Dr Pete Hay from the University of Technology in Australia believes the majority of Australians will support the actions of the protesters.
"There is so much support in this country for ending Japanese whaling that that in itself makes these sorts of in-your-face, provocative acts acceptable in a way that wouldn't have been the case if the community was more divided."
The area in which the Japanese fleet are hunting has been designated as the Southern Ocean Whale Sanctuary, designed to help whale populations recover after the devastating commercial whaling of the last century.
The following is from Radio New Zealand.
Sea Shepherd demands unconditional release of activists
The founder of the anti-whaling organisation, Sea Shepherd, says it will only accept the unconditional return of its two crew members being held on a Japanese whaling ship.
The men - one Australian and one British - were detained after boarding the Japanese vessel on Tuesday in protest at the hunting of whales in the Southern Ocean.
As a condition for releasing the two, the captain of the Yushin Maru No.2 is requesting the Sea Shepherd not interfere with its whaling operations and keep its boat at least 10 nautical miles away.
However, Sea Shepherd founder, Paul Watson, told Summer Report on Thursday the requests are unacceptable.
"What we have here is the Japanese holding hostages and making demands. That's extortion, that's the activities of a terrorist organisation," he said.
"Now they're threatening to take them back to Japan and put them on trial for piracy of all things."
Mr Watson says the Yushin Maru No.2 has not killed any whales for a week and every day they are not killing whales is a victory.
Japan intends to kill 935 minke whales and 50 fin whales in the Southern Ocean this summer, despite international criticism. Japan's Foreign Ministry says the annual hunt is not breaking international law.
A Japanese government spokesperson says the Yushin Maru No.2 has been trying to contact Sea Shepherd, but has had no response. He says they want to arrange the handover of the two men as requested by the Australian government.
A spokesman for the pro-whaling Institute of Cetacean Research, Glen Inwood, says it is considering legal action against the two activists.
Mr Inwood says the organisation has not established when the pair will be returned, but their release will not prejudice any possible future legal action. He says boarding vessels belonging to other flagged states is illegal.
Call for NZ involvement
The Green Party is calling on the Government to send a frigate to the Southern Whale Sanctuary in the Antarctic.
Conservation spokesperson Metiria Turei says the detention of the two protesters is an unprecedented situation, which could escalate.
Ms Turei says sending a frigate would demonstrate New Zealand's commitment to the integrity of the Whale Sanctuary.
However, the New Zealand Government says it has no plans to send a frigate to the Southern Ocean.