Impact of NAO on Mediterranean Fisheries

The effect of the North Atlantic Oscillation (NAO) on fisheries production has received attention in the last 2 decades, especially in relation to the inter-annual fluctuation of the important North Atlantic cod fisheries. Results of these studies show that the effects of NAO on cod stocks vary geographically, with opposite patterns in the western and eastern North Atlantic and that NAO affects mainly the recruitment success of cod, especially on heavily fished stocks. In the Mediterranean sea the number of studies is much more limited, due in part to the paucity of sufficiently long and reliable data series for Mediterranean fisheries. A recent study on the interannual variation of landings of the red shrimp Aristeus antennatus in Catalonia shows that the NAO explains a large part of the variability in population abundance with a lag of 2-3 years. New results presented here show that, at the scale of the entire Mediterranean, stocks of hake (Merluccius merluccius) respond to the NAO with different trends in the northwestern and southeastern stocks. Analysis of detailed life history data of this species in the Spanish Mediterranean coast allows to postulate the hypothesis that positive NAO years enhance hake fishery production through increasing the individual size of recruits, as well as the individual weight and abundance of adult hake. No effect on other demographic parameters such as recruitment strength or natural mortality could be demonstrated.