46 U.S.C. § 7312: Scale of employment

Individuals qualified as able seamen—unlimited under section 7307 of this title may constitute all of the able seamen required on a vessel. Individuals qualified as able seamen—limited under section 7308 of this title may constitute all of the able seamen required on a vessel of less than 1,600 gross tons as measured under section 14502 of this title , or an alternate tonnage measured under section 14302 of this title as prescribed by the Secretary under section 14104 of this title or on a vessel operating on the Great Lakes and the Saint Lawrence River as far east as Sept Iles. Individuals qualified as able seamen—limited may constitute not more than 50 percent of the number of able seamen required on board other vessels. all of the able seamen required on a vessel of not more than 500 gross tons as measured under section 14502 of this title , or an alternate tonnage measured under section 14302 of this title as prescribed by the Secretary under section 14104 of this title or on a seagoing barge or towing vessel; and not more than 50 percent of the number of able seamen required on board other vessels. Individuals qualified as able seamen—offshore. supply vessel under section 7310 of this title may constitute all of the able seamen required on board a vessel of less than 500 gross tons as measured under section 14502 of this title or 6,000 gross tons as measured under section 14302 of this title engaged in support of exploration, exploitation, or production of offshore mineral or energy resources. Individuals qualified as able seamen—limited under section 7308 of this title may constitute all of the able seamen required on board a vessel of at least 500 gross tons as measured under section 14502 of this title or 6,000 gross tons as measured under section as measured under section 14302 of this title as prescribed by the Secretary under section 14104 of this title engaged in support of exploration, exploitation, or production of offshore mineral or energy resources. When the service of able seamen—limited or able seamen—special is authorized for only a part of the required number of able seamen on board a vessel, the combined percentage of those individuals so qualified may not be greater than 50 percent of the required number. all of the able seamen required on a fish processing vessel entered into service before January 1, 1988 , and of more than 1,600 gross tons but not more than 5,000 gross tons as measured under section 14502 of this title , or an alternate tonnage measured under section 14302 of this title as prescribed by the Secretary under section 14104 of this title ; and all of the able seamen required on a fish processing vessel entered into service after December 31, 1987 , and having more than 16 individuals on board primarily employed in the preparation of fish or fish products but of not more than 5,000 gross tons as measured under section 14502 of this title , or an alternate tonnage measured under section 14302 of this title as prescribed by the Secretary under section 14104 of this title .