This is a pelagic, oceanodromous species, that seasonally can be found close to shore and can tolerate a wide range of temperatures. This species schools by size, sometimes together with Albacore, Yellowfin, Bigeye, Skipjack etc. It preys on small schooling fishes (anchovies, sauries, hakes) or on squids and red crabs. A recent study on the Mediterranean diet of this species provided evidence that juveniles prey mainly on zooplankton and small pelagic coastal fishes, sub-adults prey on medium pelagic fishes, shrimps and cephalopods, while adults prey mainly on cephalopods and larger fishes (Sarà and Sarà 2007).

This species has a maximum size over 300 cm fork length (FL), but is more common to 200 cm. Longevity is at least 35 years and possibly to 50 years (Santamaria et al. 2009).

In the Western Atlantic, this species spawns in the Gulf of Mexico from mid-April to early June at temperatures of 22.6–27.5°C, starting at age 8–10 years at around 200 cm (FL), although most individuals first spawn closer to age 12 (Rooker et al. 2007, Rooker et al. 2008, Boustany et al. 2008, Diaz et al. 2009, Collette 2010). Recently, a few larvae were collected northeast of Campeche Bank suggesting that they were spawned outside of the Gulf of Mexico (Muhling et al. 2011). Maximum age is around 32 years (Neilson and Compana 2008), although age composition structure has also changed over time (e.g., there are more younger individuals). For the most recent stock assessment, an age of first maturity was estimated to be approximately 145 kg or about age nine years in the Gulf of Mexico (SRCS ICCAT 2010). For the western Atlantic stock, the generation length is therefore estimated to be approximately 13 years based on average survivorship and fecundity across known scombrid stocks (Collette et al. 2011).

The Eastern Atlantic stock spawns in the Mediterranean Sea from May to August at temperatures of 22.5–25.5°C, starting at age three years and full recruitment is reached by age five years. There are distinct behaviours during the spawning time, most noticeably with changes in diving times and depths. Estimated relative batch fecundity is greater (more than 90 oocytes/g of body weight) than estimated for other tunas in the genus Thunnus (Sissenwine et al. 1998, Corriero et al. 2003, Rooker et al. 2007, Boustany et al. 2008, Rooker et al. 2008, Collette 2010). Fromentin and Powers (2005) reported that there is spawning site fidelity for this species both in the Mediterranean Sea and in the Gulf of Mexico. There are several spawning grounds throughout the Mediterranean. In addition, there are genetically recognizable populations within the Mediterranean (Riccioni et al. 2010).

Median sexual maturity in the Mediterranean Sea was reached at 103.6 cm (FL), and females weighing between 270 and 300 kg produce as many as 10 million eggs per spawning season (Corriero et al. 2005).

In the Eastern Atlantic stock and in the Mediterranean Sea, age of first maturity is about 3–5 years (115–121 cm FL), with a longevity of 35 years or more (Corriero et al. 2003, Santamaria et al. 2009, Rooker et al. 2007, Rooker et al. 2008). For the most recent stock assessment, an age of first maturity was estimated to be approximately 25 kg or age four years in the Mediterranean (SRCS ICCAT 2010). For the eastern Atlantic stock, the generation length is therefore estimated to be approximately seven years based on average survivorship and fecundity across known scombrid stocks (Collette et al. 2011).

Maximum Size (in cms) 458 (TL). The all-tackle angling record is of a 678.58 kg fish caught off Aulds Cove, Nova Scotia, Canada in 1979 (IGFA 2011.)