One of the fastest spreading marine invasive species across Europe is the Atlantic blue crab Callinectes sapidus Rathbun, 1896, which has been listed as one of the 100 worst marine invasive species in the Mediterranean Sea. In Portugal, the oldest record dates to 1967 in the Tagus estuary (western coast). Few records have been detected in that area until the present day, but in the southern coast (Algarve) the situation is quite different. Since 2016-17, the species is increasing in abundance and expanding its distribution towards the western coast of Algarve. Now indisputably established in southern Portugal, seasonal migrations are still poorly understood. This project aims at understanding such migrations, that change across the life spawn of this species, between higher zones of estuaries and coastal zones.