The fisherman's task in navigating his craft are threefold:

(i) to guide his craft safely and by the most direct route between his terminal ports and the fishing grounds;

(ii) to shoot, tow and haul his fishing gear in such a manner as to prevent it being damaged or becoming fast to any obstruction on the seabed;

(iii) to search for aggregations of commercial fish species and by lures, snares and the use of towed nets to capture viable quantities of the fish located.

The navigation to and from the fishing ground poses the same problems as for other marine craft, but once on the grounds, using towed or encircling nets, the position of the nets, not only horizontally but also in the vertical plane, are as much his concern as is the position of the parent vessel. Most fishing grounds are situated where there are irregularities in the seabed topography or where oceanographical factors provide a rich feeding area for a range of fish species. Alternatively many fish species carry out an annual migratory journey to their spawning areas or towards more favourable environmental conditions, their shoaling behaviour at this time making them particularly susceptible to mass capture.