Species Description 

Bluefin tuna are a majority dark blue or black, particularly on their topside with flecks of silvery-green. On their underside they have a light silver colour, dotted with grey flecks, which provides camouflage in the ocean when hunting for prey. Prey looking up below the tuna will not be able to distinguish the fish from the glare of the surface water. Likewise, prey from above will not be able to see the tuna as the dark blue colour on the fish blends in with the darkness from the deep. This is also known as counter-shading, and is seen across many marine animals.

Bluefin tuna are highly migratory, travelling across the Atlantic, Indian, and Pacific Oceans. They have been recorded up to 4.5 m (14.76 ft) in length very rarely though most largest cases sit at 3 metres (9.8 feet). On average, bluefin tuna are more around 1.5-1.8 metres (5.8 feet) and have a mean weight of 250 kg (550 lbs).

Bluefin tunas can live to be more than 30 years old but do not reach sexual maturity till they are ten years of age. This is an issue for the longevity of populations of this species as this long a period leaves them open to being caught before they have had a chance to reproduce. This is an especially prevalent in fishing techniques such are purse seine given their lack of discrimination in capture. Spawning takes place at different times of the year for schools across the world, and the location of schools in either the Western or Eastern Atlantic influences the mean egg count per fish. In Eastern Atlantic schools, mean egg count per fish sits at 13-15 million while in Western Atlantic schools, it is as high as 30-60 million.

There are 3 species of bluefin tuna: Atlantic bluefin, Pacific bluefin and Southern bluefin tuna. They are among the larger bony fishes and eat squid and fish, including sardines, mackerel, and even other tunas. Despite having the smallest eyes across all tuna species, they have impeccable vision, hunting by sight.