MARINE ECOLOGY PROGRESS SERIES Mar Ecol Prog Ser Vol. 471: 183–191, 2012 doi: 10.3354/meps09991 Published December 19 INTRODUCTION Albacore Thunnus alalunga is an epi- and meso- pelagic oceanic tuna which supports important com- mercial fisheries (Santiago 2004). It is cosmopolitan, highly migratory, and widely distributed mostly in temperate waters between latitudes 45° N and 45° S, including the Mediterranean Sea. Stocks of this spe- cies are currently overexploited, and there is an urgent need to improve its conservation and man- agement efforts (Collette et al. 2011). For conserva- tion purposes, marine organisms should be managed at the population level since the extent and dynamics of population structuring underlies resilience and sustainability (Carvalho et al. 2010). Therefore, an improvement of T. alalunga population structure assessment is necessary. Based on fisheries distribution, identification of separate spawning areas, different estimated growth rate, morphological differences, and tagging experi- ments, the International Commission for the Conser- vation of Atlantic Tunas (ICCAT), the Indian Ocean Tuna Commission (IOTC), the Western and Central Pacific Fisheries Commission (WCPFC), and the Inter- American Tropical Tuna Commission (IATTC) estab- lished 6 management units for this species, 1 per © Inter-Research 2012 · www.int-res.com *Corresponding author. Email: andone.estonba@ehu.es Worldwide genetic structure of albacore Thunnus alalunga revealed by microsatellite DNA markers Iratxe Montes 1 , Mikel Iriondo 1 , Carmen Manzano 1 , Haritz Arrizabalaga 2 , Elisa Jiménez 3 , Miguel Ángel Pardo 3 , Nicolas Goñi 2 , Carys Ann Davies 4 , Andone Estonba 1, * 1 Department of Genetics, Physical Anthropology and Animal Physiology, Faculty of Science and Technology, University of Basque Country (UPV/EHU), Leioa, Spain 2 AZTI Tecnalia, Marine Research Unit, Pasaia, Spain 3 AZTI Tecnalia, Food Research Unit, Derio, Spain 4 Commercial Fisheries Research Group, Department of Life Sciences, Galway Mayo Institute of Technology (GMIT), Galway, Ireland ABSTRACT: One of the most common problems in fisheries is the definition of management units. Albacore Thunnus alalunga is an important species for commercial fisheries. Its population struc- ture is still partially unknown; however, on the basis of fisheries data, tagging experiments, and morpho-ecological studies, 6 management units are currently accepted for this species. The main objective of this study was to define genetic entities within T. alalunga and to discuss the appro- priateness of current management units. For this purpose, 13 microsatellite loci were applied to 551 albacore samples collected worldwide, and the population genetic structure was assessed. The most relevant differences between management and genetic units were that (1) Atlantic and Indian Ocean samples are genetically indistinguishable, and (2) possible differentiation exists within the Pacific Ocean and also within the Mediterranean Sea. Thus, this study provides genetic information to clarify albacore population delimitation, which is a key factor to reach the demanded sustainable management of this resource. KEY WORDS: Albacore · Management units · Microsatellite DNA · SSRs · Population genetics · Conservation · Fisheries · Stock Resale or republication not permitted without written consent of the publisher OPEN PEN ACCESS CCESS