The fisheries for Atlantic bluefin tuna (Thunnus thynnus) were managed as two separate management units but now have a Management Procedure (MP) that explicitly considers the mixing of the two biological populations (ICCAT 2023). However, TAC advice remains area-specific, with separation at the 45 W meridian (acting as the boundary between the Western Atlantic stock and the Eastern Atlantic and Mediterranean Sea stock). 

The ICCAT Atlantic-Wide Bluefin Tuna Research Programme (GBYP) and national research programmes have provided the basis for improved biological studies. Substantial progress has been made in estimating regional, time-varying mixing rates for Atlantic bluefin tuna, using otolith stable isotope and genetic analyses (ICCAT 2023). However, critical areas like spawning schedules and natural mortality rates still require further study. For more details regarding the current knowledge of the structure of these stocks, refer to Section 9.6 of ICCAT (2023).