The Influence of the Spatial Scale on the Fishery Landings-SST Relationship

Possible effects of the spatial scale of analysis on the relationship between fishery landings and the water temperature in the Mediterranean Sea have been investigated using the FAO capture database (1970-2010). The analysis was performed by dividing species in three thermal affinity categories: cold, temperate and hot species. Results showed significant changes in fishery landings composition during the last four decades, in terms of the relative contribution of cold, temperate and hot species to landings; moreover, the presence of a strong influence of water warming in determining the landings temporal pattern has been confirmed. This relationship, however, resulted to be not homogenous across the tested spatial scales (entire Mediterranean basin, three main sub-basins, eight FAO areas). The best models (based on the Akaike Information Criterion), were the ones fitted at the finer spatial definition (i.e. the eight FAO areas) for all the three thermal affinity categories. The recorded relationship showed clear differences in terms of direction, depending on both areas and thermal affinity groups. Cold species showed a negative relationship with the increasing water temperature in all the FAO areas, being partially replaced by temperate ones, with the exception of the Adriatic and Black Sea (the coldest areas in the Mediterranean basin), where a moderate increase in the water temperature is still favoring the cold affinity group. This kind of results could be useful within the context of the management plans definition, within a context of climate changes.