Tuna is and one of the most eaten fish in the world. It belongs to a subgroup of the mackerel family and consists of 8 species that vary in colour and size. Tuna is a nomadic species and is found throughout the world's oceans. It can be eaten fresh or tinned. Tuna loin is commonly eaten raw or seared and lightly seasoned, while canned tuna is precooked for a long time and often prepared heavily dressed.