Occurence of blue whiting in trawl catches during surveys from Portugal to Faroe Islands, 1979- 1995

Abstract

Historical data on blue whiting (Micromesistius poutassou) from survey trawl stations of 7 countries, have been congregated and prepared into special files, together with corresponding temperature and salinity observations. The majority of the data originate from bottom trawl stations and hence represent the on-shelf part of the stock, i.e. mainly younger age groups. The pelagic stations, mainly worked off the shelf over deeper water west of the British Isles, represent the more oceanic part of the stock, which are both young and older age groups. These biological data are presented on maps by quarter of year and age groups. Special attention is paid to the data from the Norwegian surveys whose main target is blue whiting when this is congregated along the slope west of the British Isles to spawn. These data clearly show a south-bound tendency of the abundance with year in the 1980's. Age 1 is more frequent in the south and north than in the central area, i.e. around lat. 55° N, while older fish are more uniformly distributed. The increase in temperature and salinity southwards from lat. 59° N off North Scotland, is roughly linear, while the values North of Scotland show a much greater dispersion.