Tuna belongs to the class bony fish, mackerel order and mackerel family. They do not refer to a single fish, but to a group. This population consists of 5 genera, and 15 different species are included in the 5 genera. Their bodies are tapered at both ends, and their abdomen is the thickest part of the whole body. Tuna has a moderate mouth and smooth body surface, and most of them are blue and silver in color. Tuna is special. They can maintain their body temperature at a higher temperature than the surrounding water temperature. Moreover, they swim fast and are good at jumping, which is now regarded as the most commercially valuable fish.

Tuna is a kind of fish that lives in the ocean, but different species have different body shapes. Like yellowfin tuna, the body length in adulthood is between 1-3 meters, and those over 2 meters are generally considered to be too large. The weight of yellowfin tuna is generally over 100 kg, but generally not over 200 kg.

There are also bluefin tuna, which are about 3 meters long in adulthood, and some are too large, which can reach 4.6 meters long. They generally weigh between 200 and 400 kg, and the larger bluefin tuna can weigh more than 700 kg. Of course, there are also some smaller tuna, such as albacore tuna, which weigh about tens of kilograms in adulthood.