Satellite data to support bluefin tuna protection
A new habitat model developed by JRC scientists allows the potential presence of bluefin tuna to be tracked through daily updated maps, helping to protect endangered stocks and fight illegal fishing. Based on satellite remote sensing data, the model provides for the first time an overall view of the preferred bluefin tuna habitats in the Mediterranean Sea, as well as their changes over time.
Bluefin tuna is a commercial fish of high market value which has been strongly overexploited for 15 years. The largest stock of adults which reproduce in the Mediterranean is now at its lowest on record, around 40% of late 1950s’ level. Lower quotas, restricted fishing period and recommendations for enforced fisheries control have been some of the measures introduced in order to reverse the trend.
The JRC habitat model allows the creation of near real-time maps of feeding and spawning potential bluefin habitats in the Mediterranean Sea, as well as habitat maps over a decade. The novelty of this model is the use of satellite data on the concentration of chlorophyll on the sea surface, as well as temperature, to track specific oceanographic features, which play a key role on the fish distribution.
The results achieved through the model clearly highlighted that bluefin tuna feeding and spawning are concentrated in some recurrent locations. Areas most frequently chosen for nutrition are on the northern side of the Mediterranean. Reproduction starts in May in the eastern part of the Mediterranean and ends in July in the western part. Moreover, the results also displayed a strong seasonality in habitat size and locations, as well as high year-to-year variations for the potential spawning habitat depending on regional weather conditions. This variability is key to evaluating the pertinence of Marine Protected Areas (or sensitive areas) for this species.