The assessment and sustainable management of Atlantic blue fin tuna (ABFT) is challenged by uncertainties surrounding rates of mixing between management areas. MFRC researchers are part of an international collaboration (2014-present), led by AZTI (Spain) which aims to improve knowledge of ABFT population structure and mixing as well as age and growth dynamics. The team combines genetic techniques with analyses of otolith chemical composition and otolith shape to discriminate between populations and to resolve their migration pathways. This research is supported by ICCAT under the Atlantic Wide Research Programme for Bluefin Tuna (GBYP)