((a)) Except as provided in chapter 89 of this title and except for a vessel operating only on rivers, harbors, lakes (except the Great Lakes), bays, sounds, bayous, and canals, a vessel subject to inspection under chapter 33 of this title shall engage a minimum of licensed individuals as follows:

((1)) Each of those vessels propelled by machinery or carrying passengers shall have a licensed master.

((2)) A vessel of at least 1,000 gross tons as measured under , or an alternate tonnage measured under as prescribed by the Secretary under and propelled by machinery shall have 3 licensed mates, except—

((A)) in the case of a vessel other than a mobile offshore drilling unit, if on a voyage of less than 400 miles from port of departure to port of final destination, the vessel shall have 2 licensed mates; and

((B)) in the case of a mobile offshore drilling unit, the vessel shall have licensed individuals as provided by regulations prescribed by the Secretary under .

((3)) A vessel of at least 200 gross tons but less than 1,000 gross tons as measured under , or an alternate tonnage measured under as prescribed by the Secretary under and propelled by machinery shall have 2 licensed mates.

((4)) A vessel of at least 100 gross tons but less than 200 gross tons as measured under , or an alternate tonnage measured under as prescribed by the Secretary under and propelled by machinery shall have one licensed mate. However, if the vessel is on a voyage of more than 24 hours, it shall have 2 licensed mates.

((5)) A freight vessel or a passenger vessel of at least 300 gross tons as measured under , or an alternate tonnage measured under as prescribed by the Secretary under and propelled by machinery shall have a licensed engineer.

((b))

((1)) An offshore supply vessel of less than 500 gross tons as measured under or 6,000 gross tons as measured under on a voyage of less than 600 miles shall have a licensed mate. If the vessel is on a voyage of at least 600 miles, however, the vessel shall have 2 licensed mates.

((2)) An offshore supply vessel of at least 6,000 gross tons as measured under on a voyage of less than 600 miles shall have at least two licensed mates, provided the offshore supply vessel meets the requirements of section 8104(g)(2). An offshore supply vessel of at least 6,000 gross tons as measured under on a voyage of at least 600 miles shall have three licensed mates.

((3)) An offshore supply vessel of more than 200 gross tons as measured under , or an alternate tonnage measured under as prescribed by the Secretary under , may not be operated without a licensed engineer.

((c)) Subsection (a) of this section does not apply to a fishing or whaling vessel, a mobile offshore drilling unit when on location, or a yacht.

((d)) The Secretary may—

((1)) suspend any part of this chapter during a national emergency proclaimed by the President; and

((2)) increase the number of licensed individuals on a vessel to which this chapter applies if, in the Secretary’s judgment, the vessel is not sufficiently manned for safe operation.

((e)) The Secretary may prescribe the minimum number of licensed individuals for an oil spill response vessel.