Population dynamics and status of striped marlin (Kajikia audax) in the western and central northern Pacific Ocean

Abstract

A new understanding of the structure of striped marlin stocks in the Pacific Ocean was the basis for estimating the population dynamics in the western and central northern Pacific (1975–2010). Dynamics were estimated using large-scale spatial data and a fully integrated length-based and age-structured model. The model used fishery-dependent catch, size composition and catch per unit effort (CPUE) as likelihood components. Time-varying selectivity patterns were used in the modelling to account for changes in fishing practices. Estimates of fishing intensity showed a pattern of exploitation generally exceeding the levels associated with maximum sustainable yield (MSY). Estimates of spawning biomass and recruitment described a population that was relatively stable near biomass levels associated with MSY until the 1990s, when recruitment declined and biomass levels fell below those associated with MSY. The reduction in recruitment could be explained by a loss of spawning biomass and potentially changes in environment. The future prospects of rebuilding the stock will depend on the relative importance of the roles maternal biomass and environment play in determining recruitment strength.