Spatial variability in the growth rate of blue whiting (Micromesistius poutassou) larvae at the shelf edge west of the UK

The distribution of larval blue whiting (Micromesistius poutassou) was mapp ed along the shelf edge west of Scotland during May and June 1994. Age and individual growth histories of larvae were inferred from counts and measure ments of increments on the sagittal otoliths. Maximum abundances of larvae were at the shelf break northwest of Ireland and decreased with distance no rth. Larvae were clearly and consistently associated with a tongue of warm saline water which extended north along the shelf edge. From otolith micros tructure, the individual growth rates of larvae distributed in the warm sal ine water mass found in the south of the survey area were significantly gre ater than larvae which were distributed in cooler water further north. Howe ver, the corresponding length-weight relationships did not show any signifi cant latitudinal trend suggesting that differences in growth were not refle cted in the condition of the larvae. The consequences of slower growth and hence longer stage duration may lead these larvae to suffer higher rates of mortality and the results suggest that the dynamics of the water currents associated with the shelf break may be an important determinant of larval g rowth, and subsequently annual recruitment to the blue whiting stock. (C) 2 001 Elsevier Science B.V. All rights reserved.