Fighting Foreign Illegal Seafood Harvests Act of 2023 or the FISH Act of 2023 This bill establishes a blacklist and other mechanisms for addressing vessels involved in illegal, unreported, and unregulated (IUU) fishing. The bill requires the National Oceanic and Atmospheric Administration (NOAA) to establish the blacklist and issue regulations governing its administration. NOAA must add a vessel to the list if NOAA has a reasonable basis to believe that the vessel contributes to IUU fishing in certain ways, such as by (1) exceeding applicable catch limits; (2) engaging in fishing on the high seas involving the use of forced labor; or (3) providing nonemergency fueling, resupply, or other services to a vessel on the blacklist. Under the bill, a vessel on the blacklist is prohibited from accessing U.S. ports or making deliveries in U.S. waters. No U.S. vessel may service a vessel that is on the blacklist, except for emergency or enforcement purposes. A blacklisted vessel and its cargo, with some exceptions, shall be subject to seizure and forfeiture. Additionally, the bill requires the President to impose property- and visa-blocking sanctions on any foreign person (i.e., individual or entity) that is the beneficial owner of a vessel on the blacklist. The Coast Guard must increase its observation of vessels on the high seas suspected of IUU fishing and related practices. U.S. Customs and Border Protection must issue regulations regarding the verification of seafood imports to block imports of seafood harvested by foreign vessels using forced labor.