Migration of adult mackerel along the Atlantic European shelf edge from a tagging experiment in the south of the Bay of Biscay in 1994

Within the frame-work of the Shelf Edge Fisheries Oceanography Study (EU AI R SEFOS Project), 10 000 mackerel were tagged in March and April 1994, off the Basque Country (Spain), at the eastern part of ICES Division VIIIc, clo se to the boundary between the, so-called, Southern and Western mackerel st ocks in the north-east Atlantic. The purpose of this experiment was to outl ine the migration routes for mackerel spawning in the south-east corner of the Bay of Biscay and to examine the justification for separating a Souther n and Western stock. Recaptures were recorded along the western coasts of E urope, from the north-west of Spain to the Norwegian coast. These results c onnected the fisheries of the southern and northwestern areas and put in do ubt the existence of two separate stocks in these regions. The paper conclu des that the fishery on spawning mackerel that takes place in the east and central Cantabrian sea in the first half of every year is made on mackerel coming from the north-western area extending their southward spawning migra tion through ICES Division VIIIc, before going back to north. This migratio n pattern provides a simple explanation for the strong seasonality of the s outhern fisheries on adult mackerel and for the disappearance of those adul ts from that area during the second half of the year. (C) 2001 Elsevier Sci ence B.V. All rights reserved.