The biological studies are essential components of the GBYP research plan, particularly for better understanding the population structure of the Atlantic bluefin tuna. The efforts have been focused on the collection of hard parts for ageing and micro-constituent analysis, as well genetic sampling and related analysis. The analyses are related to ageing (using both otoliths and spines), growth, genetic studies and micro-constituent analyses for identifying possible sub-populations and micro-constituent studies for identifying the natal origin. Additional analyses have been carried out over the years, including the otolith shape, studies on additional spawning areas and specific genetic analyses for providing a further insight overview.