1. The main function of the pectoral fin is to move the body forward and control the direction or "brake" during travel. When the tail fin does not move, the pectoral fin opens to both sides of the fish body. When it swings back and forth, the fish body moves forward; when one side of the pectoral fin swings, the fish body turns to the stationary side.

2. The pelvic fins help the dorsal fin and anal fin maintain the balance of the fish body and assist the fish body in lifting and turning. The position of the pelvic fins varies with different fish species. The pelvic fins of cartilaginous fishes are generally located on both sides of the cloacal opening.

3. The dorsal fin mainly plays a balancing role in the fish body. But there are also some long-bodied fish whose dorsal and anal fins can assist in body movement and propel the body forward rapidly.

4. The basic function of the anal fin is to maintain body balance, prevent tilting and swaying, and also coordinate swimming. Most fish have one anal fin, while cod have two.

5. Caudal fin, in cartilaginous fish, the tail end of the spine is flexed dorsally. Correspondingly, the dorsal lobe of the caudal fin is developed and the ventral lobe is smaller, forming an asymmetrical crooked tail. As for bony fish, the dorsal lobe becomes smaller and the ventral lobe becomes larger, becoming a dorsoventrally symmetrical tail again.