A NUMERICAL-MODEL OF THE DISPERSION OF BLUE WHITING LARVAE, MICROMESISTIUS-POUTASSOU (RISSO), IN THE EASTERN NORTH-ATLANTIC

A numerical circulation and transport model system was used to simulat e the dispersion of larvae of blue whiting, Micromesistius poutassou ( Risso) in the eastern North Atlantic. The area of the model extends fr om the northern Bay of Biscay to the Norwegian Sea and covers the shel f-edge and adjacent waters at a horizontal resolution of around 20 km in 16 vertical layers. Larval input data were based on the long-term m ean distribution, abundance and seasonal occurrence of larvae, derived from historical information. The circulation model was run using tida l forcing and climatological density fields as well as both climatolog ical meteorological forcing and actual six-hourly wind stress fields f or 1994 and 1995. Transport from the main spawning areas to the west o f the British Isles and north of Porcupine Bank was associated with cu rrents along the shelf-edge and in the Rockall Trough. Tracers were ei ther dispersed to the north and north-east along the shelf-edge, exten ding into the northern North Sea and Norwegian Sea, or were retained i n the Rockall Gyre and over Porcupine Bank. A less intense southerly f low from Porcupine Bank was observed both under climatological conditi ons and in the 1995 simulation, when winds were more variable than in 1994. The results based on the 1995 meteorological conditions showed t he most extreme retention of tracers in the Rockall Trough/shelf-edge area west of Scotland and a low penetration of tracers onto the shelf. These results are discussed in relation to the observed distribution of O-group juveniles and to indices of year-class strength - in partic ular, in relation to the 1995 year class, which is the highest year-cl ass estimate of blue whiting on record.