The yellowfin tuna is large compared to other tunas. They can reach 6 feet, the size of a tall man. It’s body is strong and is deepest under the dorsal fin. Adults have a very long second dorsal fin. A band of scales form a circle around the body just behind the head. They have small eyes and teeth and metallic dark blue or green bodies with white undersides. Their most distinct feature is the golden stripe along their sides. Bright yellow fins also stand out. They can live 15 years.
The yellowfin tuna lives in the upper 330 feet of the water, in temperatures of 65 to 88 degrees. They swim in mixed schools with skipjack, bigeye, and other tunas. In the eastern Pacific they are known to swim with dolphins. They often school under drifting objects, possibly for protection or laying eggs. They prey on fish, cephalopods, and crustaceans. They eat near the surface during daylight hours.
Yellowfin are popular targets for commercial fishermen. Yellowfin tunas are found around the world in tropical and subtropical waters. Near Pacific ocean islands, they are still caught by hook and line. They are highly migratory yet stay within certain regions. There is little genetic exchange between regional subspecies.