1 Dorsal fins are found on the back of the fish. 2  There may be up to three of them. 3  The fish uses this fin for balance in the water and sudden movements. 4  Caudal fins are also known as tail fins.5  This is what we refer to as the fish's tail. 6  Anal fins are on the ventral (bottom) surface of the fish, behind the anus. Dorsal fins are found on the back of the fish. 2  There may be up to three of them. 3  The fish uses this fin for balance in the water and sudden movements. 4  Caudal fins are also known as tail fins.