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Mysterious to science
Nicknamed "the lord of the seas", the bluefin tuna fascinates as much as it intrigues. Capable of traveling thousands of kilometers in its lifetime (which can exceed 40 years), this giant of the oceans, which can grow to several meters in length and weigh several hundred kilograms, is still something of a mystery to science. Its migratory routes, feeding grounds and behavior in the face of environmental variations remain difficult to decipher.
Mission Thon Rouge
To lift the veil, the "Mission Thon rouge" program, launched in 2025 in Royan, relies on an innovative collaborative approach. Last summer, the first campaign resulted in the tagging of around twenty individuals. This success has led scientists to consider the waters around Royan as a strategic study area in the Atlantic.
Valuable data
At the heart of the system: electronic tagging. After no-kill capture, the fish are fitted with scientific tags before being released. These increasingly sophisticated devices collect invaluable data. Some "archiving" tags continuously record depth, water temperature and luminosity, making it possible to reconstruct fish trajectories. Others, known as "pop-up satellites", detach after a programmed period to transmit data via satellite, offering a global view of migrations. Finally, acoustic beacons can be used locally to track movements in areas equipped with receivers.
These technologies enable us to better understand the seasonal movements of tuna, identify their hunting grounds and analyze the influence of ocean conditions on their behavior.
But this success also relies on the expertise of recreational anglers. Their knowledge of the field, their ability to locate fish and to fight them under the right conditions make them essential partners. A close collaboration that illustrates the emergence of a sport fishing sector committed to science.
Supported by the City of Royan, Ifremer and SNSM, the program will continue with a new campaign scheduled for early August 2026. The ambition is clear: to refine knowledge of this emblematic species in order to adapt management measures and guarantee its long-term preservation.
In Royan, bluefin tuna is no longer just a trophy. It has become a messenger for the oceans.
