An acoustic survey targeting blue whiting (Micromesistius poutassou) spawning and post spawning aggregations in the north east Atlantic in March/April 2010. Spawning takes place from January through to April along the shelf edge from the southern Porcupine Bank area northwards to the Faroe/Shetland Ridge including offshore areas as the Rosemary, Hatton and Rockall Banks. Peak spawning occurs between mid-March and mid April and acoustic surveys are timed to occur during this phase. Acoustic data were collected using the Simrad ER60 scientific echosounder.Biological sampling was done using a single pelagic midwater trawl.Fish samples were divided into species composition by weight. Species other than the blue whiting were weighed as a component of the catch. Measurements of blue whiting lengths were recorded. Age, length, weight, sex, maturity and stomach fullness data were recorded. CTD (conductivity, temperature, depth) casts were also carried out. One day in total was lost to weather downtime. 1. Assess the size of the spawning stock of blue whiting along the shelf break area to the W and NW of Ireland and to the W of Scotland and offshore banks. 2. Collect biological samples by trawling to determine the age structure of the stock 3. Carry out vertical CTD casts to determine the temperature and salinity profiles of the water mass.