Environmental variability in the North Atlantic and Iberian waters and its influence on pelagic fish: the cases of horse mackerel and albacore

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Time series of environmental variables that characterizes the atmospheric and oceanic variability, such as the North Atlantic Oscillation (NAO) index, the oceanic transport given by differences in Potential Energy anomaly (PEA), the position of the Gulf Stream index (GSI) and local variables as air and sea surface temperature, precipitation, wind, mean sea level and Ekman transport in the western and northern Iberia have been analysed. The system dynamics was characterized using a factorial Principal Component Analysis (PCA) of all variables. PCA of the abiotic parameters from 1966 to 2000 shows the first component as a thermal axis, setting up air and sea surface temperatures (positive semi-axis) against intensity of spring/summer upwelling (negative semi-axis), explaining around 19% of variability. The second component relates to the oceanic transport indices as PEA and GSI, explaining around 12%, and the third relates to sea level and NAO. The following components are related to the annual and autumn Ekman transport, and wind components. Total explained variability is 64%. Periods of different hydro-climatic conditions have been characterised as well as strong shifts. PCA has also been related to two cases of pelagic fishes: horse mackerel (coastal) and albacore (oceanic). In this context, horse mackerel recruitment is found correlated with the thermal/upwelling first component (r=.78). A Multiple Regression analysis has been effectuated for both pelagic fishes, Sea Surface Temperature (SST), Upwelling index and 2-year lag NAO index explain 67% of the horse mackerel recruitment variance and the PEA index and the NAO index explain the 47% of the albacore age 3 catches variance.