This advance notice of proposed rulemaking announces a control date (the date of the action's publication in the Federal Register) with respect to the future entry of U.S. purse seine and longline fishing vessels in highly migratory species fisheries in the western and central Pacific Ocean. For purse seine vessels, the control date would also apply to the future expansion of the carrying capacity or well volume of vessels already in the fishery. Furthermore, the advance notice of proposed rulemaking would give notice that even if the future participation of a new or expanded-capacity purse seine vessel is allowed in the fishery, the vessel's future allowable level of fishing effort and/or catch might be limited. The advance notice of proposed rulemaking would also solicit public comments on possible ways to establish limits on purse seine fishing capacity. This action is being taken to implement a conservation and management measure adopted by the Commission for the Conservation and Management of Highly Migratory Fish Stocks in the Western and Central Pacific Ocean, of which the United States is a member. The measure is for the conservation and management of bigeye tuna, yellowfin tuna, and skipjack tuna in the western and central Pacific Ocean. The scope of the rulemaking might be expanded at the proposed rule stage to implement additional provisions of the conservation and management measure.