California Code, Fish and Game Code - FGC § 7880

(a) A person owning or operating a vessel used in connection with fishing operations for profit who has been issued a commercial boat registration pursuant to Section 7881 shall display, for the purpose of identification, a department registration number on the vessel in a manner designated by the department.

(b) The method of displaying the registration number on the vessel shall be determined by the department after consultation with the Division of Boating and Waterways, taking into consideration the responsibilities and duties of the Division of Boating and Waterways as prescribed in the Harbors and Navigation Code.

(c) The registration number is not transferable, and it is a permanent fixture upon the vessel for which it is originally issued.