Costa Rica promises shark activist a fair trial BERLIN (Reuters) - The president of Costa Rica promised on Wednesday a fair trial in her country for a Canadian conservationist facing possible extradition over a campaign against shark finning, and tried to calm his fears of revenge attacks by Costa Rican shark fishers. Paul Watson, founder of the Sea Shepherd marine conservation group, was arrested 10 days ago in Germany because of an arrest warrant from Costa Rica then freed on 250,000 euros ($319,200) bail, pending a German ruling on the extradition request. Forbidden from leaving Germany and obliged to report twice a day to police in Frankfurt where he was detained, Watson made a brief appearance in Berlin on Wednesday at a protest coinciding with a state visit by Costa Rican President Laura Chinchilla. Hundreds of his supporters demonstrated outside the Bellevue palace of the German president in Berlin during Chinchilla's official reception, chanting "Free Paul Watson!" and waving banners that said "Save Our Skipper!" "My concern is not with getting a fair trial in Costa Rica, rather the sharking 'mafia' over there having put out a $25,000 contract on my life," Watson told Reuters Television. The charges stem from a confrontation on the high seas in 2002 between his ship and a vessel involved in illegal shark finning, which involves catching sharks, slicing off their fins and tossing the sharks back into the sea, sometimes barely alive. The Costa Rican president, calling Watson's campaign "a legitimate cause," told reporters inside Bellevue that if he did return to Costa Rica, she would make sure he was fairly treated. Her country's authorities have three months to formalize an extradition request which would then be evaluated by a regional court in Frankfurt, a German justice ministry spokeswoman said. "If he does have to return to Costa Rica, he will not only have the proper rigorous protection, but he can also count on having a legal process which will strictly follow the law," said Chinchilla, the centrist Costa Rican leader. Watson said he was encouraged by the support shown by people and officials in Germany. "The policeman who arrested me said sorry, the judge handling my case was also really sorry and the guards in prison asked for autographs," he said. "Merkel should free him right away," said Tanja Umbash, a Sea Shepherd supporter attending the protest in Berlin. Reporting by Elisa Oddone; Editing by Stephen Brown