An acoustic survey targeting blue whiting (Micromesistius poutassou) spawning and post spawning aggregations in the north east Atlantic from 26th March to 15th April 2013 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. To facilitate a more coordinated spatio-temporal approach to the survey participating countries meet annually to discuss survey methods and define effort allocation at the ICES led Working Group International Pelagic Surveys (WGIPS). The 2013 survey covered the core spawning area of blue whiting to the west of Ireland, Scotland and the Faroes-Shetland ridge. The survey was part of an international collaborative survey using the vessels RV Celtic Explorer (Ireland), FV Vilnus (Russia), RV Tridens (Netherlands) and the RV Magnus Heinason (Faroes). Transect design and effort allocation was pre-agreed. A parallel transect design was used to allow transect interlacing in co-surveyed targetareas (east-west orientation). Acoustic data were collected using the Simrad ER60 scientific echosounder. Cruising speed was maintained at a maximum of 10 Kts (knots) where possible. Biological sampling was done using a single pelagic midwater trawl.All components of the catch were sorted and weighed; fish and other taxa were identified to species level. Oceanographic data on temperature, depth and salinity (CTD) were collected at set stations. Visual surveys for cetaceans and seabirds were undertaken between 27th March and 11th April 2013, with sightings of any other marine mega fauna recorded. 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. 3. CTD data collection. 4. Take part in inter-calibration exercise for acoustic data gathering with biological samples.