There has been some support for the existence of a unique stock of Atlantic chub mackerel in the NE Atlantic, e.g. Zardoya et al. (2004) recognizes a panmictic population with gene flow between the Mediterranean Sea and the Atlantic Ocean; however (Costa et al. 2011), basing their findings on analysis of parasites, ponder the occurrence of different stock units along the Eastern Atlantic. The FAO CECAF assesses chub mackerel within NW African waters as a single stock (FAO 2020). A recent ICES workshop mentioned potential distribution boundaries in the Cantabrian Sea and also in the Straits of Gibraltar, which would support the separation of a NW African stock, but the connectivity of the Mediterranean distribution is unclear. Further studies are underway (ICES 2020).