The Japan Coast Guard on Friday arrested a member of U.S.-based antiwhaling group Sea Shepherd Conservation Society for trespassing in connection with his boarding of a whaling fleet vessel in the Antarctic Ocean last month.

New Zealander Peter Bethune, 44, was arrested at 11:16 a.m. Friday by the coast guard on the Shonan Maru No. 2, which entered Tokyo Bay at around 10:45 a.m.

Bethune climbed aboard the Japanese vessel after approaching apparently unseen on a Jet Ski.