Swordfish monitoring by a GIS-based spatial and temporal distribution analysis on harpoon fishery data: A case of study in the central Mediterranean Sea

Abstract

The Geographic Information Systems (GIS) was used to support fishery analyses aimed to monitor the swordfish harpoon fishing and analyze temporal and spatial patterns of catch distribution, also in relation to the environmental parameter Sea Surface Temperature (SST). The study was carried out in an important reproductive area of the Mediterranean Sea, including the Strait of Messina and nearby areas (south-eastern Tyrrhenian Sea and north-western Ionian sea). These locations also represent the unique fishing ground of the Italian swordfish harpoon fishery.Fishery, environmental and biological data were collected between 2002 and 2011 from fishermen’s logbooks and by observations on-board of fishing vessels during swordfish harpoon fishing season (May to August). Data were organized into a database and structured on a geographical reference to allow a quantitative multi-parameter modelling through the GIS tools.The application of GIS allowed a good visualisation of catch distribution patterns, underlining annual and monthly differences in resource availability to fishery. The analysis of GIS maps showed a change in swordfish behaviour, likely related to SST anomalies and, as a consequence, difference in catch and effort distribution patterns. These differences were more evident if fishes in pair were considered. GIS turned out an important and powerful tool to analyze fishing information; the production of georeferentiated maps helps scientist to an easier interpretation of data on large pelagic resources. The proposed GIS-based analysis can add new information on swordfish and help decision makers in the Mediterranean swordfish management.