Since 1976, France participates to the International Bottom Trawl Survey (IBTS), coordinated by the International Council for Exploration of the Sea (ICES). The main objective of these surveys, which are carried out on board of research vessels, was to obtain annual forecasts of recruitment for the various commercial fish species of the North Sea. These estimates were used by ICES Working Groups to assess these various stocks and to propose management measures for the following year. In addition, the data collected during these surveys concerned biological and abundance analysis of main commercial fish species exploited by European countries in the North Sea. The results of studies were published in scientific papers and have improved knowledge in this field. Working methods were standardised in order to keep consistency in results. For instance, the trawl used (Grande Ouverture Verticale net) was the same on each research vessel.