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Sardine regime shifts off Portugal: a time series analysis of catches and wind conditions

Decadal changes have been observed in the annual catch of sardine (Sardina pilchardus W). Long-term changes have also been observed in alongshore winds off Portugal in the last decades in winter months. During sardine spawning season (winter), northerly winds that favour upwelling led to unfavourable conditions for egg and larval survival. By using time series analysis, we investigated the effect of wind conditions and North Atlantic Oscillation (NAO) on the sardine catches, in the period from 1946-1991. We also investigated the time lag between recruitment strength and its turnout in catches. We concluded that recruitment is forced to a lower level when the frequency and intensity of northerly wind exceeds a certain limit in winter. Our time series retrospective analyses led to evidence of climatic driven regime-shifts in West Portugal sardine productivity in late 1960s-early 1970s. These results are discussed in terms of their implications in fisheries management plans.