Merchant Marine vessels are administered by a number of "parallel hierarchies" depending upon the type of vessel, assigned mission, and the number of crew onboard.
Right: Sirius Class Cargo Vessel
The most common command chain on a merchant vessel is the Underway Watch. Maintained while a merchant vessel is underway in space, the underway watch mans all vital stations on board with qualified crewmen. Watch personnel are drawn from the various merchant departments, which provide the administrative chain of command; a permanent command structure overseeing the day-to-day running a merchant vessel. Each merchant department is overseen by a department head, normally a licensed merchant officer, assigned by merchant warrant rates who are in turn assisted by several crewman.
The last type of merchant command chain, which does not exist on all merchant vessels, is the In-Port Duty Section. The In-Port section comprises approximately one third of the vessel's crew who remain onboard when the vessel is docked at a morning facility, such as a shipyard or starbase. The purpose of the In-Port Duty Section is to provide enough personnel onboard in order to respond to an emergency. The duty section is led by a Section Leader, who is assisted by a number of Duty Department Heads. The remainder of the duty section consists of Duty Section Members, who simply serve as "extra bodies" in the event of an onboard emergency.
STANDARD MERCHANT MARINE ORGANIZATION
For certain vessels, such as military transports and hospital ships, during periods of permanent mooring the entire vessel's crew departs and the ship is powered down into a status known as "Lay-up". Lay-up status is normally only used for special purpose merchant craft which are not required to be active unless a specific mission is at hand.
Former Starfleet personnel seeking Merchant Marine employment are typically granted advanced positions depending upon prior experience and Starfleet service. Prior Starfleet service may be divided three distinct categories.
Former Starfleet Crewman are normally accepted into the Merchant Marine in the lateral position of Merchant Crewman. Recruits who separated under Entry Level Discharges may only join the Merchant Marine as Landsmen.
Former Starfleet Petty Officers and Chief Petty Officers are encouraged to apply for a Warrant License prior to seeking employment in the Merchant Marine. The Petty Officer/Chief Petty Officer may then begin their Merchant Marine service in an appropriate Warrant billet; if no Warrant billet is available, such persons may be also rated as an Able Crewman. Those not obtaining a license prior to seeking employment are normally rated as a standard Crewman.
Starfleet Officers are encouraged to apply for a professional license so as to begin thier Merchant Marine service as a licensed officer, although some former Starfleet officers do apply for Warrant Licenses while still others have been known to join the Merchant Marines as Crewman.
Former Starfleet officers with extensive experience (such as former starship commanders, first officers, chief engineers, etc) may be permitted to apply directly for a higher license without holding a lower prerequisite license.