Spatio-Temporal Distribution and Stock Assessment of Striped Marlin (Kajikia audax) in the Western and Central North Pacific Ocean

Habitat characteristics of Striped Marlin, Kajikia audax, in the western and central North Pacific Ocean (WCNPO) were examined using generalized additive models by modelling fishery catch-rates as a function of remotely-sensed environmental covariates, including sea surface temperature (SST), chlorophyll-a concentration (CHL), mixed layer depth (MLD) and sea-surface height anomalies (SHA). SST explained the largest proportion of the deviance, and was therefore considered the best predictor for the habitat of striped marlin. Spatial distributions of the relative density of striped marlin indicated that there is a seasonal north–south migration. The standardized CPUE series for Taiwanese longline, as well as those from the Japanese distant-water, Japanese costal, and Hawaiian longline fleets were used in a non-equilibrium surplus production model (ASPIC) to assess the stock status of striped marlin in the WCNPO. Results showed that the maximum sustainable yield (MSY) estimated for this stock was 4,812 tons, and that the stock was both overfished and subject to overfishing. The values of B₂₀₁₀/B_MSY and F₂₀₀₉/F_MSY were estimated at 0.20 and 2.53, respectively. The projection analysis suggested that the total allowable catch (TAC) should be reduced to 1,700 tons per year for sustainable use of this resource.