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 (e.g. Wilding et al., 1998; discussion in Beaumont and Gjedrem, 2007). Here, based on the respective Scottish assessment areas, five stock 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.