European Ocean Biodiversity Information System

The Scottish West Coast Surveys use a similar ICES rectangle based sampling strategy to that used in the North Sea. Trawl stations are selected at one tow per rectangle based on a library of clear tows. There is no explicit return to the same trawling position every year, although this is generally the case. Since 1999 the potential for using a depth rather than rectangle based stratification has been under investigation. To this end, and where possible, those rectangles which display substantial internal depth variation have been sampled twice at different depths. The recent inclusion of samples collected between 200 and 500m would suggest that depth stratification should be initiated as soon as possible. The survey covers Division Via and extends into the northern part of the Irish Sea and north west of Ireland. The depth range covered has been 20 to 500m since 2000. The survey is usually carried out in March of each year. The target species are cod, haddock, whiting, saithe and herring and age frequencies are constructed for these species. All other fish species encountered are also sampled for at least length frequencies. Indices of abundance at age are calculated for all the target species and these data are used at the Northern Shelf Assessment Working Group and also made available for the Herring Assessment Working Group.