Tuna is a large marine organism. Its body surface is relatively smooth, and the lines of the whole body are relatively smooth. Tuna is long and round as a whole. They are the thickest in the middle of their bodies, tapering at the back, and the tail is the thinnest part of the whole body. Their fins are not big, their tails are like crescent or fork, and there are obvious ridges on both sides of the tail handle. Tuna has a dark back color and metallic luster on both sides. Common tuna colors are blue or silver. Of course, there are different colors, but they are rare.

There are many species of tuna. They belong to a group, and there are 5 genera and 15 species of tuna in this group. These five genera are Bonito, Bonito, Tuna, Bonito and Tuna. Different genera contain different species of tuna. The smallest tuna is bonito, which is about 50 cm long and weighs about 1.8 kg in adulthood. The largest tuna is Atlantic bluefin tuna, which can grow up to 4.6 meters long and weigh up to 684 kilograms. The more famous tuna species are yellowfin tuna, bluefin tuna and albacore tuna. These kinds of tuna are fresh and tender in meat and high in protein content, which makes them the most commercially valuable fish in the world.