There are two stocks of albacore tuna (Thunnus alalunga) in the Pacific Ocean, one in the Northern Hemisphere and the other in the Southern Hemisphere. The North Pacific stock consists of all albacore tuna present in all waters in the Pacific Ocean North of the equator to 55°N (IATTC 2019).

The discreteness of these stocks is supported by fishery data, with lower catch rates in equatorial regions (Suzuki et al. 1977), tagging data (indicating there are no South Pacific Ocean recoveries of fish tagged in the North Pacific Ocean (Ramon 1996), ecological data (albacore larvae are rare in samples from equatorial waters (Ueyanagi 1969), and genetic data, with genetic differentiation between North and South Pacific albacore (Takagi 2001, Vaux et al. 2021). Thus, the North Pacific albacore is assumed to be a discrete, reproductively isolated stock, with no internal sub-group structure within the stock (ISC 2020).

For the North Pacific Albacore fishery, distant-water longline fleets and distinct domestic longline fleets catch adult albacore over a broad geographic range in the North Pacific region (see map). This fishery presents an overlapping area between the Western and Central Pacific Fisheries Commission (WCPFC) and the Inter-American Tropical Tuna Commission (IATTC). However, management and compliance monitoring is attributed only to the WCPFC. The stock assessments for the North Pacific albacore are currently conducted by the Oceanic Fisheries Program of the Secretariat of the Pacific Community (SPC) (WCPFC 2021).

The Parties to the Nauru Agreement (PNA) is a regional binding treaty-level instrument to facilitate cooperation in the management of fisheries resources of common interest. The agreement requires the management of straddling/highly migratory fish stocks on a subregion basis through Regional Fisheries Management Organizations (RFMOs), and the WCPFC Convention (the regional fisheries agreement covering the WCPFC convention area). PNA members are simultaneously members of the WCPFC, so a single management unit is set for PNA-related profiles.