A new habitat model, developed by the JRC and partner scientists, detects areas and periods where Atlantic bluefin tuna prefers to feed and spawn. Covering most of the areas where this species lives and the entire area subject to fisheries, the model provides concrete recommendations on when and where grounds should be closed to increase yield and stability of this fishery sector in the long term.
The identification of potential feeding and spawning habitats of a given species is key information for decision makers to operate limited and efficient fishing closure and to ensure high recruitment levels or even stock recovery if overfished. The daily mapping of preferred habitat allows implementing dynamic closure schemes in space and time, which are more efficient than the traditional fixed-closure systems. The habitat results may additionally help to improve the estimate of bluefin tuna stocks by informing on probable population distribution and movements.
The habitat model correlates the presence of bluefin tuna with environmental data from satellite observations and ocean circulation models. It considers favourable environmental conditions, including food availability and physical tolerance to temperature and water currents, and both spawning and feeding behaviours. With respect to existing models, the JRC tool predicts the preferred habitat of two size classes: juveniles (5-25 kg, only feeding behaviour) and adults (> 25 kg). It provides daily high resolution maps of the core habitat of the species in the Mediterranean Sea, the North Atlantic and the Gulf of Mexico.
Whereas feeding habitats for large fish were found in northern parts of the Atlantic (the Norwegian Sea in the east and the Gulf of Saint Lawrence in the west), for small fish they were mostly located in temperate zones of the North Atlantic, in the Mediterranean Sea and subtropical waters off north-west Africa. For spawning, the Gulf of Mexico was found suitable from March-April in the south-east to April-May in the north, and the Mediterranean Sea from mid-May in the east to mid-July in the west.
As such, the habitat model supports the implementation of the Common Fisheries Policy, which seeks to restore and maintain fish stocks at sustainable levels, puts an end to wasteful fishing practices and paves the way for a dynamic and smart fisheries management. This tool will furthermore monitor the habitat variability under the effect of climate change and ensure the adaptability of future regulations and fishing activities.