The Indian Ocean Tuna Commission (IOTC) is an intergovernmental organisation mandated to manage tuna and tuna-like species in the Indian Ocean and adjacent seas. In 2015, the European Union provided funding to the IOTC for a project to describe the population structure and connectivity of four tuna species (albacore, bigeye, skipjack and yellowfin), three tuna-like species (kawakawa, longtail tuna and narrow-barred Spanish mackerel), three billfish species (striped marlin, swordfish, Indo-Pacific sailfish) and one shark species (blue shark) within the Indian Ocean. The project used DNA sequencing of the fish populations and made a substantial contribution to the knowledge of the population structure of these 11 important species related to tuna fishing in the Indian Ocean. The project has now ended and a brief overview of the background, activities and achievements of the project has been published. See the project webpage at https://iotc.org/projects/iotc-population-structure-iotc-species-indian-ocean-estimation-next-generation-sequencing for all relevant documents or contact [email protected] for more information. The IOTC’s objective is to promote the conservation and optimal utilization of tuna and tuna-like stocks covered by the IOTC Agreement, and to encourage sustainable development of fisheries. Its establishment was approved by the FAO Council in 1993 and the IOTC came into force in 1996.