Tuna is a fish. They are a kind of fish with high commercial value. A family of marine fishes belonging to the family Mackerelidae, Perciformes, Teleost. The tuna family contains 15 species of tuna, and different species of tuna have different shapes and habits. Their heads and tails are thin, their bellies are round, and they look smooth as a whole. Their mouths are moderate and their teeth are well developed. Tuna is mostly metallic in color, with blue and silver in the majority. Their body surface is smooth and looks like scaleless fish.

Tuna likes to live in warm waters, so they are found in tropical and subtropical waters all over the world. But now the number of tuna is relatively small, mainly concentrated in the Pacific Ocean, Atlantic Ocean and Indian Ocean. Tuna generally lives in the sea area at a depth of 100-400 meters, and some of them live at a position about 50 meters above the water surface.

Tuna swim faster. They can swim 60-80 kilometers an hour on average. The fastest speed can reach 160 kilometers. Their gills have degenerated, and they need different activities to ensure that they have enough oxygen. Even when sleeping, tuna will keep moving.