1. Different dorsal fins: The dorsal fin colors of blue marlin and tuna are different. Most of the dorsal fin colors of blue marlin are yellow and blue, and there are some rare other colors. Tuna's dorsal fin is reddish brown.

2. The snout is different: The mouth of blue marlin is pointed and the snout is very long. Tuna's mouth is not very big, and its snout is round. There is a big difference between the two from the mouth and kiss.

3. Different habits: Blue marlin and tuna live in different waters. Blue marlin likes to live in the upper layer of warm sea area, and their adaptability is poor, mainly living near the warm isotherm of 24 ℃ on the surface.

Blue marlin is a rare pelagic fish in warm ocean water, which belongs to Perciformes, swordfish and marlin. Blue marlin is delicate and has poor adaptability to the environment, so most of them live near the isotherm of 24 ℃. They will migrate north and south with the seasons, mainly living at a depth of about 40 meters. Of course, they are also found in the deep sea of 1,000 meters, but they are extremely rare. Blue marlin is a carnivorous fish, which mainly feeds on squid, tuna-like fish, crustaceans and cephalopods. Larger blue marlin will move alone, while smaller blue marlin will move together.