Lecture Notes, Nat. Vert., Emporia State Univ. These notes are provided to help direct your study from the textbook . If you were to study only these notes, you would not learn enough to do well in the course.
Fins provide a means of control.
By pushing against the water with its fins, a fish can control its motion in these three direction. Fins actually allow very precise control and this gives the fish the ability to orient its jaws relative to a food source or other object to be manipulated by the jaws. This can really be brought home by watching fish feed in the often turbulent and seemingly chaotic flow of water over a coral reef. Fins allowed fish to greatly increase speed and agility when moving about. The dorsal and anal fins control yaw.