Motorized boats about 10 m long and powered with 70 HP engines, suitable for reaching both deep and shallow areas, were used to reach the fishing areas. The perimeters of the fishing areas were mapped using a GPS (UTM coordinates). During the navigation, while the fisherman sailed along the area according to his knowledge, the perimeter points were registered. Geographical references such as the main shallow areas (bancos) and estuarine islands were also recorded. At each field trip around 100 GPS points were registered that pooled together allowed the identification of each fishing area. It took about 8 working hours to map the perimeter of one specific area of the estuary.