Electronic tagging data and habitat envelope modeling used to monitor spatial persistency and possible relocation of spawning grounds for the bluefin tuna in the East Atlantic and the Mediterranean Sea

A spawning habitat envelope has been created for bluefin tuna in its traditional spawning ground in the Mediterranean Sea by combining environmental variables and species behavior. We used logistic regressions through a generalized linear model (GLM) approach to determine whether reproduction was affected by spawning habitat characteristics and individual behavior. Results from the implementation of the model predicted a high probability of occurrence of reproductive events associated with 17 tagged tuna. Some of them matched the already well known spawning grounds in the Mediterranean Sea (the area around the Balearic Islands, the Tyrrhenian Sea and the Gulf of Sirte). The model also proposed some other areas seldom or not at all mentioned in the bibliography in both, the Mediterranean and the Atlantic Ocean, such as the Alboran Sea, the Catalan Sea, the Gulf of Lions and the Bay of Biscay. This model provides an objective methodology to predict and adapt spawning areas, and to identify other potential but unknown, or even new, spawning areas and periods for the species. Moreover, the application of the present methodology could help the implementation of an adaptive management approach for Atlantic bluefin tuna by predicting areas suitable for spawning and identifying changes in spawning areas and season in the currently highly changing ocean and climate conditions.