Pete Bethune, captain of the anti-whaling Sea Shepherd Conservation Society vessel Ady Gil, was arrested Friday in Japan for allegedly trespassing on a Japanese whaling ship last month.

Bethune has been detained on the Shonan Maru No. 2 since Feb. 15 when he allegedly boarded the ship after approaching on a jet ski. Bethune's boat was also damaged during the last whaling season after it collided with the Shonan Maru No. 2 in January.

Bethune's arrest marks the first time that the Japan Coast Guard has attempted to prosecute for trespassing in international waters.

Bethune was a part of the Sea Shepherd's campaign to prevent whaling by Japan this year. Japan claims that it hunts whales for scientific research purposes only, while Sea Shepherd argues that the meat is smuggled onto the marketplace for eating.

Sea Shepherd is currently preparing to mount a legal challenge against Japan to stop the country from hunting whales.