Atlantic bluefin tuna, a growing sea giant

Large bluefin tuna before release © Guillaume Fourrier

The Atlantic or Mediterranean bluefin tuna is a formidable hunter. This giant of the seas can measure 3 m and move at speeds of up to 70 km/h. A sport fish par excellence for thrill-seekers.

Guillaume Fourrier Published on September 4, 2023

Scientific name

Thunnus thynnus (Linné, 1758)

Morphology

Bluefin tuna have an elongated, fusiform body. It is massive and built for fast swimming. Its first dorsal fin is yellow or bluish, while the second is higher and reddish-brown. Its back is dark blue, and its lower flanks and belly are silvery with colorless transverse stripes alternating with rows of colorless dots.

Thon rouge en chasse — Bluefin tuna hunting

Fishing spots

Bluefin tuna are found in the Atlantic and Mediterranean. In France, they migrate increasingly northwards, crossing as far as the English Channel. They swim in open water, mainly on the surface and at mid-depth. It's usually necessary to head out to sea in search of concentrations of fish, especially near large drop-offs and ocean fronts. Satellite and meteorological readings can be used to find them, thanks to surface temperature fronts and the presence of plankton (chlorophyll), which can be found using TimeZero software.

A good depth sounder allows you to follow the evolution of the bluefin tuna's swimming depth to anticipate bites and be ready.

Thon rouge montant sur l'amorÃ§age effectuÃ© au Stonfo Ã 70 m de fond — Bluefin tuna rising on Stonfo bait at 70 m depth

Fishing techniques

Bluefin tuna is caught in 3 main ways. The first is by grazing. This involves continuous baiting by cutting sardine cubes at regular intervals or using a robotized baiter. The rods are placed at different depths and a balloon placed on the surface of the water allows you to quickly see the slightest touch. Powerful rods and spinning reels are highly recommended.

Combat avec un thon rouge pris au broumÃ© — Fight with a bluefin tuna caught in a scramble

Another technique is free-line fishing with a livebait. You can set a livebait on a scramble or throw the livebait on a chase and leave the pick-up open to let the unsuspecting tuna gobble. Last but not least, you can approach flushes to stalk tuna using hard lures such as poppers and jerkbaits.

Panoplie de leurres pour le thon rouge au lancer-ramener — A wide range of lures for bluefin tuna trawling

You can also cast a small soft lure such as a comma behind a bubble.

Reproduction

Bluefin tuna approach the Mediterranean coast in spring to spawn, particularly in Spain. They live in waters above 14°C with a salinity of at least 3.5%. Bluefin tuna grow to a size of 25 to 30 cm (350 to 500 g) at 3 months, 60 to 70 cm (3.5 to 5 kg) at 1 year, 1.35 m (35 to 40 kg) at 5 years, 2 m (150 kg) at 10 years and 2.50 m (250 kg) at 15 years.