Every year an aerial survey takes place from the first of August to the end of September. It consists in counting the number of schools over the Gulf of Lions. The evolution from one year to another is used to build an index of abundance that is used within ICCAT for the stock assessment.
If we don't see many tunas during the aerial survey, does it mean there are not many tunas in the sea or does it mean they moved somewhere else ? Is the environment affecting such movements ? Tagging activities allow to understand individual behaviour and to answer such questions. Ifremer has been leading tagging activities in the Mediterranean for a very long time and has current activities in the Gulf of Lions, in the Atlantic and on the Maltese spawning ground.