Assessment of West of Scotland whiting (ICES Division VIa) using multiple survey data

This paper presents an assessment of West of Scotland whiting based only on research vessel survey data. Recent ICES assessments have used data from the IBTS quarter 1 (IBTSq1) survey and commercial catch at  age data, but problems with likely bias in reported catches has meant that only a limited range of years of commercial data have been included in the assessment. As a result in the assessment, values for the period 1995-2005 are dependent largely on the single survey abundance indices. By way of exploration this paper considers an assessment with all the catch data omitted to avoid possible biases resulting from misreporting but includes the four available surveys. Each survey has its weaknesses associated with design, changes in gear and vessel and yeas of missing data. However, it is perhaps useful to investigate how the surveys perform in an assessment to gauge the possible impact they have on the parameter estimates and to see how far the assessment can be taken without the use of commercial data.