Greenpeace says its activists have targetted fishing boats from South Korea, Taiwan and the United States in high-seas protests against what is says was the plundering of tuna in the Pacific.
A spokesman says in the latest confrontation, crew from the Greenpeace ship Esperanza boarded a Taiwanese boat, the Nian Sheng 3, to inspect their catch.
Greenpeace campaign leader, Lagi Toribau told the news agency AFP that the captain of the tuna boat allowed the activists to board.
Over the weekend, Esperanza crew members hopped in a small boat to paint the side of the US vessel Cape Finisterre with the words Tuna Overkill.
Last week, the group protested alongside the South Korean ship Olympus before activists confiscated a fish aggregation device used to attract tuna.
Mr Toribau of Greenpeace says the fishing carried out by the foreign ships is technically not illegal but is unregulated.
He says as tuna catches in other oceans have declined because of overfishing, these ships have moved into the Pacific.