An acoustic survey targeting blue whiting (Micromesistius poutassou) spawning and post spawning aggregations in the north east Atlantic in 2019. This survey took place in March/April on board the RV Celtic Explorer. The purpose of this survey was to survey blue whiting spawning stock using acoustic techniques in coordination with vessel from other participating vessels. Biological sampling of echotraces was carried out to determine species composition, age, spawning state and age profiles of blue whiting. Measurements of both vertical and horizontal physical oceanographic conditions were encountered along the pre-determined cruise track and part inter-calibration exercises conducted between vessels when required to determined acoustic and trawl performance. 1. Survey the blue whiting spawning stock using acoustic techniques in coordination with vessel from other participating vessels. 2. Biological sampling of echotraces to determine species composition, age, spawning state and age profiles of blue whiting