This paper describes the seasonal and geographical distribution of mackerel (Scomber scombrus, L.) and horse mackerel (Trachurus trachurus, L.) in the northern coast of Spain (ICES Division VIIIc and Sub-division IXa North), based on commercial catches and bottom trawl surveys. Mean monthly commercial catches were mapped by ICES statistical rectangle, and the quarterly distribution by age group (0,1,2 and >2 years) and by Sub-division (Sub-division VIIIc East, VIIIc West and IXa North) are presented for the period 1989 to 1994 in the case of mackerel, and 1990 to 1994 for horse mackerel. Series of catch per unit effort by age are also analysed for some commercial fleets.The age group distribution (0,1,2 and >2 years) in autumn, based on information from bottom trawl surveys, is presented for the whole area studied.The data analysis reflects clear seasonality of mackerel in the northern coast of Spain. Nevertheless, in the case of horse mackerel in the same area, seasonality is not so evident. These results are discussed with respect to spawning and feeding migrations of these species in the Northeast Atlantic.

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