Circulation-driven dispersal and retention affect blue whiting recruitment dynamics in the Northeast Atlantic Ocean

Environmental drivers of early life-stage survival are critical to understanding recruitment variability and improving ecosystem-based fisheries management. We investigate how regional ocean circulation influences blue whiting (Micromesistius poutassou) recruitment in the Northeast Atlantic by combining multi-decadal transport analyses with Lagrangian particle simulations. Using ocean reanalysis, we compute 28-year (1993-2020) volume transport indices across the Ellett Line, a hydrographic section through the main spawning grounds, and we relate them to interannual variation in recruit per spawner. We also simulate larval dispersal from main spawning areas (Porcupine Bank, Rockall Trough, Rockall Plateau, Hebrides) during the six highest and lowest recruit-per-spawner years using an agent-based particle-tracking model. Statistical models show that higher recruit per spawners are produced in years with stronger northward flow along the Hebrides-Rockall Trough (upper 0-100 m), whereas transport over Rockall Plateau is weaker and exhibits no consistent relationship with recruit per spawner. Complementary particle-tracking simulations reveal that high-recruit-per-spawner years are characterized by larger northward advection of eggs and larvae from the Hebrides, as well as increased local retention over Porcupine Bank. In contrast, low-recruit-per-spawner years exhibit more meandering drift in the Rockall region and a modest southward dispersal from Porcupine Bank. These results suggest that both effective transport to known northern nursery areas and retention in productive spawning regions can enhance early survival, depending on spawning location. We propose that large-scale ocean-climate variability (e.g., changes in subpolar gyre circulation driven by wind stress curl) modulates these transport mechanisms, thereby influencing whether early life stages are delivered to favorable habitats or lost to suboptimal areas. Our findings provide a mechanistic link between climate-driven circulation changes and fish recruitment variability, underscoring a potential benefit of incorporating oceanographic processes into ecosystem-based fisheries management strategies.