In response to the increasing use of FADs in the purse seiner tropical tuna fishing, legal binding measures have been implemented by RFMOs to limit the number of FADs used by vessel. Broad terminology referred to buoys and FADs use is included in different management measures which should be standardized among RFMOs and precisely defined to avoid subjectivity on the interpretation and harmonize the verification system. To provide detailed definitions and consistent with the buoy use and dynamics, and to clarify and facilitate the monitoring of the number of FADs used by a vessel or a fleet among RFMOs, the buoy dynamic is described and detailed definition for terms used by RFMOs are proposed.