50 CFR § 600.730 - Facilitation of enforcement.
(a) General. The operator of, or any other person aboard, any fishing vessel subject to parts 622 through 699 of this chapter must immediately comply with instructions and signals issued by an authorized officer to stop the vessel and with instructions to facilitate safe boarding and inspection of the vessel, its gear, equipment, fishing record (where applicable), and catch for purposes of enforcing the Magnuson-Stevens Act or any other statute administered by NOAA and this chapter.
(1) For the purposes of this section “freeboard” means the working distance between the top rail of the gunwale of a vessel and the water's surface. Where cut-outs are provided in the bulwarks for the purpose of boarding personnel, freeboard means the distance between the threshold of the bulwark cut-out and the water's surface.
(2) For the purposes of this section, “pilot ladder” means a flexible ladder constructed and approved to meet the U.S. Coast Guard standards for pilot ladders at 46 CFR subpart 163.003 entitled Pilot Ladder.
(1) Upon being approached by a USCG vessel or aircraft, or other vessel or aircraft with an authorized officer aboard, the operator of a fishing vessel must be alert for communications conveying enforcement instructions.
(2) VHF-FM radiotelephone is the preferred method for communicating between vessels. If the size of the vessel and the wind, sea, and visibility conditions allow, a loudhailer may be used instead of the radio. Hand signals, placards, high frequency radiotelephone, or voice may be employed by an authorized officer, and message blocks may be dropped from an aircraft.
(3) If other communications are not practicable, visual signals may be transmitted by flashing light directed at the vessel signaled. USCG units will normally use the flashing light signal “L” as the signal to stop. In the International Code of Signals, “L” (.-..) means “you should stop your vessel instantly.” (Period (.) means a short flash of light; dash (-) means a long flash of light.)
(4) Failure of a vessel's operator promptly to stop the vessel when directed to do so by an authorized officer using loudhailer, radiotelephone, flashing light signal, or other means constitutes prima facie evidence of the offense of refusal to permit an authorized officer to board.
(5) The operator of a vessel who does not understand a signal from an enforcement unit and who is unable to obtain clarification by loudhailer or radiotelephone must consider the signal to be a command to stop the vessel instantly.
(c) Boarding. The operator of a vessel directed to stop must:
(1) Guard Channel 16, VHF-FM, if so equipped.
(2) Stop immediately and lay to or maneuver in such a way as to allow the authorized officer and his/her party to come aboard.
(3) Except for fishing vessels with a freeboard of 4 feet (1.25 m) or less, provide, when requested by an authorized officer or observer personnel, a pilot ladder capable of being used for the purpose of enabling personnel to embark and disembark the vessel safely. The pilot ladder must be maintained in good condition and kept clean.
(4) When necessary to facilitate the boarding or when requested by an authorized officer or observer, provide a manrope or safety line, and illumination for the pilot ladder.
(5) Take such other actions as necessary to facilitate boarding and to ensure the safety of the authorized officer and the boarding party.
(d) Signals. The following signals, extracted from the International Code of Signals, may be sent by flashing light by an enforcement unit when conditions do not allow communications by loudhailer or radiotelephone. Knowledge of these signals by vessel operators is not required. However, knowledge of these signals and appropriate action by a vessel operator may preclude the necessity of sending the signal “L” and the necessity for the vessel to stop instantly. (Period (.) means a short flash of light; dash (-) means a long flash of light.)
(1) “AA” repeated (.-.-) is the call to an unknown station. The operator of the signaled vessel should respond by identifying the vessel by radiotelephone or by illuminating the vessel's identification.
(2) “RY-CY” (.-. -. - -.-. -. - ) means “you should proceed at slow speed, a boat is coming to you.” This signal is normally employed when conditions allow an enforcement boarding without the necessity of the vessel being boarded coming to a complete stop, or, in some cases, without retrieval of fishing gear which may be in the water.
(3) “SQ3” (... - .- ... - ) means “you should stop or heave to; I am going to board you.”