identifier that is never reused and accompanies the ship throughout its life, regardless of the changes that occur with respect to the flag, the name or the owner. Currently the International Maritime Organization (IMO) number is the only globally recognized IUB for fishing vessels.
These include international radio call signs (IRCS), maritime mobile service identification number (MMSI) and national registration numbers, and should only be linked to one ship at a time (if used correctly). However, these identifiers change when a ship changes flag, and can be reused; so it does not represent a true IUBs