50 CFR § 635.6 - Vessel and gear identification.
(a) Vessel number. For the purposes of this section, a vessel's number is the vessel's official number issued by either by the U.S. Coast Guard or by the appropriate state agency.
(b) Vessel identification.
(1) An owner or operator of a vessel for which a permit has been issued under § 635.4, other than an HMS Angling permit, must display the vessel number—
(i) On the port and starboard sides of the deckhouse or hull and on an appropriate weather deck, so as to be clearly visible from an enforcement vessel or aircraft.
(ii) In block Arabic numerals permanently affixed to or painted on the vessel in contrasting color to the background.
(iii) At least 18 inches (45.7 cm) in height for vessels over 65 ft (19.8 m) in length; at least 10 inches (25.4 cm) in height for all other vessels over 25 ft (7.6 m) in length; and at least 3 inches (7.6 cm) in height for vessels 25 ft (7.6 m) in length or less.
(2) The owner or operator of a vessel for which a permit has been issued under § 635.4 must keep the vessel's number clearly legible and in good repair and ensure that no part of the vessel, its rigging, its fishing gear, or any other material on board obstructs the view of the vessel's number from an enforcement vessel or aircraft.
(c) Gear identification.
(1) The owner or operator of a vessel for which a permit has been issued under § 635.4 and that uses handline, buoy gear, harpoon, longline, or gillnet, must display the vessel's name, registration number, or Atlantic Tunas, HMS Angling, or HMS Charter/Headboat permit number on each float attached to a handline, buoy gear, or harpoon, and on the terminal floats and high-flyers (if applicable) on a longline or gillnet used by the vessel. The vessel's name or number must be at least 1 inch (2.5 cm) in height in block letters or Arabic numerals in a color that contrasts with the background color of the float or high-flyer.
(2) An unmarked handline, buoy gear, harpoon, longline, or gillnet, is illegal and may be disposed of in an appropriate manner by NMFS or an authorized officer.