The first version of this manual was prepared in 1994 (Bertrand coord, 1994) in the frame of a concertation between several research Institutes from the four Mediterranean member States of the European Union. The target was to conduct a common bottom trawl survey in which all participants use the same gear and the same methodology. The manual was revised in 1995 after the '94 survey to take methodological improvements acquired during the first survey into account. During the years in which the project has been conducted several improvements were made. The third version of this manual was edited in 1999 to take all the modifications adopted by the Steering Committee of the project into account. This fourth version is an English translation of the former one. In addition the files formats and the files names was modified in 2000 to allow to code the year on 4 characters instead of 2 formerly and these changes have been included. Furthermore and following some trial made during the 2000' French survey some modifications of the gears rigging have been made possible.