Anti-whaling activists on hunger strike

The three Australian activists being held on a Japanese whaling security vessel are on a hunger strike, with an environmental group saying this was the plan all along.

Geoffrey Tuxworth from Perth, Simon Peterffy from Bunbury and Glen Pendlebury from Fremantle, all from the group Forest Rescue Australia, boarded the Shonan Maru 2 on Sunday off the southwest coast of Western Australia.

They have been detained by the Japanese vessel's crew and could be taken to Tokyo to face piracy and trespass charges, sparking a diplomatic incident.

Forest Rescue Australia spokesman Rowan Davidson told AAP today the three men were now on a hunger strike.

"That was the plan all along, that they would go on board and be on a hunger strike," Mr Davidson said.

"What is making it difficult is that Simon has high cholesterol and does not have his medication with him.

"Glen also has ADHD and didn't bring his medication with him either."

Mr Davidson said the trio had hoped the Japanese vessel would return the men to Australian shores.

Meanwhile, Errol Tuxworth said his son Geoffrey, 47, had called his parents on Saturday and told them he and two other men were going out to sea to protest against whaling.

However, Mr Tuxworth said he had no idea his son planned to protest by boarding the vessel.

He is pleading with the federal government to help rescue his son but says he has received very little communication.

"We've been trying to talk to the government but we can't really do anything more for him," he said.

Mr Tuxworth said he knew his son had his mobile phone with him when he went out to sea.

"We tried to ring him but he didn't answer," Mr Tuxworth said.

"But it wasn't switched off, so I think they must have taken it off him."

Mr Tuxworth said his son was an artistic man who enjoyed painting and the arts, even working as a roadie for a few years, and was currently a stage construction technician.

He said Geoffrey first became involved in activism when they lived in Victoria and he opposed tree logging in forests.

"Then he started to support the anti-whaling campaign, which my wife and I also support," Mr Tuxworth said.

"I never expected him to board a vessel, though."

Meanwhile, a group of about 45 people gathered at the Japanese consulate in Perth to support the three detained men.

Mr Davidson said there was a strong police presence there and no one from the consulate addressed the crowd.

- AAP