Ocean-climate conditions one year prior to spawning drive recruitment success of blue whiting

Blue whiting, Micromesistius poutassou, is a key prey and predator in Northeast Atlantic food webs and supports one of the largest commercial fisheries in the Atlantic Ocean. Recruitment varies 10-fold across years, creating challenges for forecasting and sustainable management. Here we focus on a key atmospheric driver of ocean variability (wind stress curl: WSC), which may affect recruitment through several mechanisms, including meridional transport, vertical mixing, plankton production, and frontal positions. The location of the transition zone between cyclonic and anticyclonic WSC in the Rockall region coincides with the location of the largest known blue whiting spawning area. We show that WSC lagged 1 year behind spawning co-varies with recruitment for 43 years and has stronger prediction skill than forecasts based on current assessment procedures or a Ricker model. The 1-year lag is consistent with a literature-reported ca. 1-year response time of ocean properties to WSC variations in this region. Major recruitment variations can now be predicted earlier and more reliably than previously possible, potentially influencing fishery advice and conservation risk for the stock under varying WSC conditions. Our findings highlight a potential mechanistic driver that could help inform sustainable and ecosystem-based management practices for this important fishery resource.