NEAFC request on effects on assessments of historical unaccounted landings for mackerel and the utility of new and existing surveys

WGWIDE carried out a thorough analysis of the potential levels of underreporting over time and the sensitivity of the assessment to this uncertainty (Annex 3 in ICES, 2013c). The assessment showed sensitivity to such uncertainty, resulting in higher biomass with higher historical catch estimates. ICES decided to reject the assessment as a basis for advice. As a consequence, the advice is now based on the on recent landings, but this advice is seen as a temporary interim measure. ICES will attempt to incorporate more stock size information in an appropriate assessment model at the benchmark in 2014. Should this approach be unsuccessful a DLS approach will be developed based specifically on the triennial regime of survey data