Striped Marlin
Striped marlin (Kajikia audax) are found throughout the tropical and subtropical regions of the Pacific and Indian Oceans. In the north Pacific region, the Western and Central North Pacific stock is bounded by the equator and the Western and Central Pacific Fisheries Commission (WCPFC) management boundary at 150ºW.
Striped marlin are predominately taken as incidental bycatch from fisheries in Japan, the USA, China, Taiwan, Korea, and other WCPFC countries. Catch of striped marlin were highest in the 1970s to the 1990s and were mostly by driftnet, but since the 1990s, they have been primarily caught by longlines and overall catches have decreased.
Because striped marlin are highly migratory species and cross international boundaries, their populations are assessed on an international scale. The stock is assessed by the International Scientific Committee for Tuna and Tuna-like Species in the North Pacific (ISC) Billfish Working Group (BILLWG), which is a collaborative effort between multinational and multi-regional fisheries management organizations that conducts assessments and provides scientific advice for swordfish and marlin species.
The most recent stock assessment of WCNPO striped marlin was conducted in 2023. The assessment model was an integrated, age-structured model in Stock Synthesis. The model included biological and fishery data (catch, catch-per-unit-effort, and length composition data from 1977 to 2020) collected from ISC and WCPFC countries. The assessment indicated that the stock was overfished and undergoing overfishing according to \(\small{ 20\%\ SSB_{F=0} }\) based reference points where \(\small{ 20\%\ SSB_{F=0} }\) is calculated by the average dynamic \(\small{B_0}\) from the last twenty years, achieved by projecting the population forward to equilibrium with \(\small{F=0}\) in each year.