| Abstract |
A series of satellite images on sea surface temperature distribution and chlorophyll a concentration, processed under a Geographic Information Systems, were used for the study of the relationship between the spatiotemporal behaviour of large pelagic fish, as revealed from fisheries data for swordfish and tuna, and their environment, as described from the identification of oceanographic features and the calculation of spatial and environmental characteristics. Tuna and swordfish abundance distribution, as derived from fishery data, was placed near productive gyres, transient eddies, large-scale thermal fronts and along warm surface currents, such as the Levantine Intermediate Water. High abundance values were observed in areas of high primary productivity, characterized by mesoscale oceanographic features and mapped with GIS methods. The studied species seem to aggregate near upwellings, thermal fronts and gyres. The nature of the relationship of large pelagic fish and mesoscale productive features could not be determined, either due to the low spatial analysis of the fishery data, or because large predators can not be directly linked to primary productivity (Schick et al., 2004). The relationship between abundance index and statistical values of environmental (sea surface temperature and chlorophyll concentration) and spatial parameters, was studied by developing Generalized Additive Models (GAMs), as this statistical method can describe non linear relationships. Sea surface temperature was proven to be the most significant of the environmental parameters that were calculated. The optimum surface temperature for the aggregation of swordfish during the reproduction period is 240C and 220C for tuna. During the pro- and post reproduction periods low temperatures, indicative of upwelling or front presence, seem to favour tuna and swordfish accumulation. The temperature values, as derived from the GAMs, were used for the mapping of potential reproductive zones in the eastern Mediterranean.
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Συσχέτιση αλιευτικών δεδομένων μεγάλων πελαγικών ιχθύων με περιβαλλοντικές παραμέτρους στην ανατολική μεσόγειο
