In the UK, the small fishing vessel of between 30 metres and 40 metres registered length requires two Deck Officers, one holding a valid Class 1 (Fishing Vessels) Certificate and the other holding a valid Class 2 (Fishing Vessels) Certificate (Olsen, 1995). Consequently, such vessels are often referred to as 'double ticket', although only one of the officers will be in charge of the vessel at any one time. The electronic equipment carried in the wheehouse of 'double ticket' vessels generally consists of full radio communications often with an Imarsat-C system, a colour video track plotter together with an interfacing Global Positioning System (GPS) possibly digital, radar systems of different frequencies, two or more echosounders, one or two (horizontal) sonars and possibly a netszonde (an acoustical system of transducers for monitoring the position of, and fish entering, the net). For pelagic (mid-water) trawlers and seiners the latter is essential for efficient fishing. Frequently, systems are duplicated to provide additional information ( for example, two echosounders of differing frequencies), the second system also acting as a backup. From previous work (Mills, 1993), the skipper's tasks in the wheelhouse while fishing require the use of the video plotter/navigation system, the echosounders, the horizontal sonar and the netszonde often more or less simultaneously in order to position the vessel and the net for optimum fish capture. Thus, in this paper, it is to these systems that criteria from ergonomic theory will be applied in order to ascertain the best possible positioning. Two wheelhouses of 'double ticket' vessels will be used to illustrate the validity of the criteria.