In-Season Marine Distribution Tracking Model for Highly Migratory Pacific Salmon Stocks

The ocean migrations of Pacific salmon that range over great distances in the marine environment have been the subject of extensive study in an attempt to better understand both distribution patterns and factors that may be affecting survival. Each age cohort of a Pacific salmon stock following a particular migration pattern will experience different patterns of vulnerability to ocean fisheries leading to specific patterns of exploitation. A proportion of each run cohort is also vulnerable to variable harvest rates spatially and temporally within a single ocean fishery. In-season management tactics (e.g., time/area closures) are often used to achieve stock specific harvest control rules, however the local spatial and temporal distribution dynamics of these stocks in local marine waters remain highly uncertain. These important details have not been formally incorporated into assessment models for in-season management of highly migratory Pacific salmon stocks.  We developed a lagrangian migration algorithm to simulate the movement of salmon stocks based on run migration timing aggregates through a one-dimensional discretized spatial scale position along the coast of North America on a weekly time step.  The results of this analysis can be used to update in- season management options for spatially complex, mixed-stock fisheries.