The Max Weber cruises were the first systematic description of the seasonal patterns in occurrence of the demersal fish fauna in the western Wadden Sea. The second extensive inventory of the demersal fish fauna of the western part of the Dutch Wadden Sea took part from October 1963 to October 1964 by regular monthly trawling surveys in the Marsdiep and Vlie basin. The programme was initiated and supervised initially by dr. Freek Creutzberg and in the course of time taken over by dr. Mark Fonds. Sampling took place with RV Ephyra, launched in 1963 as successor of RV Max Weber. In contrast to the previous survey by RV Max Weber, fishing was done with an otter trawl instead of a beam trawl on a number of fixed stations. All the fish were identified and measured on board. In total 16 cruises each of about 44 hauls were performed. The programme lasted for more than a year.