European hake (Merluccius merluccius) is widely distributed over the Northeast Atlantic shelf, from Norway to Mauritania, with a larger density from the British Islands to the south of Spain (Casey and Pereiro, 1995) and in the Mediterranean and Black sea. Although, as demonstrated by several studies (Castillo et al. 2005)(Pita et al. 2013)(Pita et al. 2011), there is no evidence of multiple populations in the Northeast Atlantic, ICES assumes since the end of the 1970s two different stock units: the so called Northern stock, in Division 3.a, Subareas 4, 6 and 7 and Divisions 8.a,b,d, and the Southern stock in Divisions 8.c and 9.a, along the Spanish and Portuguese coasts. The main argument for this choice was that the Cap Breton canyon (close to the border between the Southern part of Division 8.b and the more Eastern part of Division 8.c, i.e. approximately be-tween the French and Spanish borders) could be considered as a geographical boundary limiting exchanges between the two populations (ICES 2013).