Brittany and Scottish populations are genetically different (Beaumont et al. 1993) but the stock structure of the species is not clear despite several genetic studies conducted (Wilding et al. 1998) (Beaumont et al. 2007)). Here, based on the respective Scottish assessment areas, five assessment units are defined: West of Kintyre, NW Scotland, Orkney, NE Scotland and East Coast Scotland; the East Coast England stock is assumed, in the lack of better information, to cover the remaining English east coast. The assessment areas were defined by Marine Scotland to reflect the characteristics of the fisheries in the past rather than on the basis of evidence to support discrete populations. Similar trends in recruitment across the West of Kintyre and North West and also in Shetland, the North East and East Coast suggest that there are linkages between some of these areas at prerecruitment stages with similar trends in survival to age of recruitment (Dobby et al. 2012).