DISTRIBUTION OF LARVAL AND JUVENILE FISH IN THE WESTERN IRISH SEA - RELATIONSHIP TO PHYTOPLANKTON, ZOOPLANKTON BIOMASS AND RECURRENT PHYSICAL FEATURES

In the western Irish Sea, differences in tidal currents and water dept h create seasonal hydrographic regions. The summer stratified region h as an associated cyclonic gyre of near-surface water. Each region has a distinct seasonal cycle of phytoplankton production, and the coastal region is one of the most important fish spawning areas in the Irish Sea. The abundances of larval fish and newly metamorphosed pelagic juv eniles were negatively and positively correlated with depth, respectiv ely, suggesting that fish that spawn in the coastal region do not spen d all of their early life stages inshore. The distribution of larvae a nd O-group pelagic fish reflects the close coupling between recurrent hydrographic features and biological production. The coastal region su pports early and sustained primary production and generally a higher b iomass of zooplankton in early spring than the offshore mixed and stra tified regions. Later in the year, pelagic O-group fish are associated with a greater biomass of zooplankton in the summer stratified region . The movement of pelagic O-group fish into the summer stratified regi on may result from the entrainment of a southerly flow of coastal wate r into the western Irish Sea gyre. The seasonal gyre may physically re tain these pelagic fish within the western Irish Sea during the summer .