Dorsal fin: Keeping fish upright plays a key role in fish balance. If you lose it, you will lose your balance and turn over.

Pectoral fin and ventral fin: Balance. If you lose balance, the fish will swing from side to side.

Tail fin: determines the direction of movement. If you lose it, the fish won't turn.

Gluteal fin: coordinate other fins and play a balance role. If you lose it, your body will shake slightly.

Fins can also sense current, so they won't be lost.

Fish are divided into pectoral fin, ventral fin, dorsal fin, anal fin and caudal fin. The dorsal fin and the gluteal fin play a balance role. Fins can help change direction and act as brakes. The ventral fin helps the pectoral fin to brake. When a fish swims, it swings its body from side to side, tightens its muscles to make an S-shaped movement, and pushes back the water to make its body move forward. After the fins are tied, the fish can still go forward and turn, but its body is wobbly and its abdomen turns over carelessly. Fish also move forward by swinging their tail fins, just like rowing a boat when sailing.