The Pelagic thresher shark (Alopias pelagicus) is an oceanic species whose biology and behavioural ecology are largely unknown due to study limitations. Fisheries and by-catch data indicate that it is found in warm and temperate offshore waters, that it matures late, has low fecundity and is vulnerable to over-exploitation. International conventions have recognized some shark species to be ‘threatened’, promoting nations to implement protection policy, but species listed comprise those which have received comprehensive scientific investigation, and whose biology and behavioural ecology are well understood. Knowledge that Pelagic thresher sharks regularly visit a seamount in the Philippines presents an unique opportunity to study this rarely observed oceanic shark. Preliminary investigations at this site during 2005 identified significant relationships between shark presence and cleaning activity conducted by resident Cleaner and Moon wrasses (Labriodes dimidiatus and Thalassoma lunare). Cleaning activity relating to sharks has never been investigated in the wild before, but the observable interactions seen at this site explain why these mainly oceanic sharks venture into shallow coastal waters, where they are vulnerable to fishing and disturbance from dive tourism. Understanding their behavioural ecology will provide important information to aid initiatives to protect them.
Photo Credits by: ©ThresherSharkResearchandConservationProject