DOES THE WESTERN IRISH SEA GYRE INFLUENCE THE DISTRIBUTION OF PELAGICJUVENILE FISH

The western Irish Sea is an important spawning and nursery ground for many commercially exploited fish. Spawning begins in the Irish coastal regions in early spring, and moves offshore as the season develops. A s a result of the onset of seasonal hearing in spring, stratification isolates a dome of cold bottom winter water in the deep (> 100 m) basi n of the western Irish Sea. The resultant density fields drive a cyclo nic gyre which dominates the circulation of the region during late spr ing and summer and is characterized by anticlockwise current speeds wh ich exceed 0.2 m s(-1), after removal of tides. Surveys of pelagic juv enile (O-group) fish in 1994, 1995 and 1996, showed that they were coi ncident with the centre of the gyre. Physical data from 1994 and 1995, were used to describe the horizontal and vertical structure of the wa ter column and the associated circulation regime. The behaviour and sw imming speeds of pelagic juvenile fish were insufficient to explain th eir apparent shift in abundance away from the coast to the central wes tern Irish Sea. Drifter and current data suggested that their entrainm ent into the gyre could provide both the transport and retention mecha nisms. (C) 1997 The Fisheries Society of the British Isles.