Marine wildlife activist Paul Watson, currently on bail in Germany pending a decision on whether to extradite him to Costa Rica, vowed Tuesday that his campaign will go on even if he is tried and jailed.

"They hope that by getting me out of the way, they'll shut down our operations. They won't," Watson told AFP in a telephone interview.

"This is not about me. It is about our oceans and the ever-escalating threat of diminishment of the diversity of life in our seas. It is about the sharks, the whales, the seals, the sea turtles and the fish," the 62-year-old activist said.

Watson was arrested at Frankfurt airport on May 14 and detained for a week before being released on bail.

He told AFP he has been placed under "house arrest" and was obliged to report to the police twice daily.

"I want to make it very clear that whatever happens to me will not affect our campaigns," he said in a separate written statement emailed to AFP.

Watson is the leader of the Sea Shepherd Conservation Society, whose ships he said would continue to "defend sharks in the South Pacific, whales in the Southern Ocean Whale Sanctuary" and dolphins in Taiji, Japan.

"Fortunately, Sea Shepherd is now much bigger than myself... and if I am prevented from serving on the front lines upon the high seas I will serve as a symbol of resistance to the destruction of our oceans from inside a prison cell."

Watson said he planned to travel to Berlin on Wednesday to participate in a rally by his supporters on the occasion of a visit by Costa Rican President Laura Chinchilla to the German capital.

"But I have to be back in Frankfurt by 5:00 pm (1500 GMT) when I have to report to the police," he added.

In Berlin, he hoped to meet members of Chinchilla's delegation to press for assurances for his personal safety should he really be extradited and face trial in Costa Rica, he said.

"Although I have no reason to believe that the Costa Rican legal system would not give me a fair trial, my concern is not for the judicial system, but for the reality that the shark fin mafia of Costa Rica has a price on my head and a Costa Rican prison would provide an excellent opportunity for someone to exercise this lethal contract against me," he said.

"We have cost the shark finners a great deal of money over the last two decades and they want their revenge. I would need absolute assurance that the Costa Rican authorities would not place me in a position to jeopardise my safety when I return to Costa Rica to prove my innocence in court."

The charges against Watson stem from a high-seas confrontation over shark finning in 2002.

Sea Shepherd claims it was escorting an illegal shark finning ship back to port when the crew falsely accused the organisation's members of trying to kill them.

Watson is accused of "putting a ship's crew in danger".

He said it was unusual that an extradition order should be issued for "a relatively minor offence, where no one was injured and no property damaged."

Watson suggested that Japan might be "putting pressure" on Germany to carry out the extradition order.

"It may be more than coincidental that the extradition order was put out in October 2011 at around the same time that the Japanese brought civil charges against us -- and lost -- in a Seattle court," he said.

The Canadian national is well known for his pursuit and harassment of Japanese whaling boats off Antarctica, which in recent years has significantly reduced the number of animals slaughtered.

Sea Shepherd has adopted increasingly militant ways to halt the hunt, to Tokyo's irritation.

This year the group hurled stink bombs at the boats on the high seas and used ropes to try to tangle their propellers in a series of exchanges that saw the whalers retaliate with water cannon.