Feasibility study combining North Sea and Atlantic mackerel egg surveys

Mackerel Scomber scombrus is a widely distributed species with a high economic and ecological importance. The North East Atlantic mackerel comprises three different spawning components. The Spawning Stock Biomass (SSB) index from the mackerel egg surveys is used as a fisheries independent tuning index for the mackerel assessment. The North Sea mackerel triennial egg survey is carried out in the year after the egg survey of the Western and Southern spawning components. Due to this time lag currently the North Sea egg survey SSB index is not used directly in the mackerel assessment. However, the egg survey is the only available information on the mackerel spawning component in the North Sea. Can the North Sea mackerel egg survey index be incorporated in the mackerel assessment and what is the impact of the incorporation of this index? Could the North Sea and Atlantic egg surveys be carried out in the same sampling year?