Skipjack in the WCPO is considered a single stock for assessment purposes (Vincent et al. 2019 and references cited therein). In the western Pacific, warm, pole-ward-flowing currents near northern Japan and southern Australia seasonally extend their distribution to about 40ºN and 40ºS. These limits roughly correspond to the 20ºC surface isotherm.

A substantial amount of information on skipjack movement is available from tagging programs, which have documented some large-scale movement within the Pacific  (Vincent et al. 2019 and references cited therein). In general, skipjack movement is highly variable and is thought to be influenced by large-scale oceanographic variability.

The FishSource profile is based in a single Assessment Unit (Western and Central Pacific Ocean, WCPO) and a single Management Unit (Western and Central Pacific Fisheries Commission, WCPFC), since the WCPFC is the RFMO managing highly migratory stocks in the WCPO. Fleets from the different fishing countries considered in FS represent Commission Members, Cooperating Non-members and Participating Territories to the WCPFC, and therefore they have obligations under the convention including the application of WCPFC conservation and management measures (CMMs). All members of the PNA agreement are also members of the WCPFC.

The Parties to the Nauru Agreement (PNA) is an Oceania subregional agreement between the Federated States of Micronesia, Kiribati, Nauru, Palau, Papua New Guinea, Solomon Islands, Tuvatu, and the Marshall Islands. The PNA coordinates the implementation of management measures with a view to enhancing economic benefits from the fishery. Member countries of the PNA have adopted and implemented distinct Vessel Day Schemes for the longline and purse seine fisheries, whereby they allocate fishing days to a  country which are sold to the highest bidder. The PNA unassociated (free school) fishery was MSC certified in 2011. All the PNA parties are, in turn, Members of the WCPFC.