Population genomics of coastal Pacific Hake

Objective: Understanding the genetic structure of harvested fishery species is crucial for accurate stock assessments and effective management strategies. There have been several rangewide population genetic analyses of Pacific Hake Merluccius productus; however, a thorough focus on the heavily harvested coastal stock off the west coast of North America is missing. Recent observations of spatial-temporal variability in life history and migratory patterns of the coastal population have brought into question whether this variation may be related to genetic differentiation. Methods: Here, we used restriction site-associated DNA sequencing markers to thoroughly assess the potential for spatial-temporal genetic differentiation in the coastal stock of Pacific Hake. We sampled during different seasons from British Columbia down to the U.S.-Mexico border over multiple years on what traditionally have been thought to constitute spawning and feeding grounds, resulting in the most comprehensive assessment of coastal Pacific Hake population structure to date. Result: Generally, our results suggest very weak to no structure among coastal spatial-temporal sites and corroborate previous findings of strong differentiation between coastal and Salish Sea populations. The lack of structure among coastal sites is likely due to significant amounts of gene flow in this highly migratory population. Conclusion: These findings align with the ongoing management strategy for coastal Pacific Hake, which is based on an annual stock assessment that considers the coastal stock homogenous and distinct from the Salish Sea population. The understanding that management units indeed match genetic populations provides managers with additional confidence in existing management strategy.