Movement is one of the most important animal behaviors because it enables the animals to react to the changing conditions of the environment. The fishes have to move for a variety of reasons. The main reason for fish movement is mainly the search of food. Fish movement holds a lot of challenges. One of the challenges is the density of water which makes it difficult for the fish to move. Fish movement involves a challenging interaction of the forces under the water. These forces include thrust and drag. Thrust and drag are two forces in opposing directions. A movement occurs when thrust is greater than drag. Other forces that the fish encounter in their movement are the water movements. The strong currents in the waters possess enough power to even carry the animals. Fish movement involves the use of skeleton, fins and muscles. The skeleton facilitates the simple physics of swimming while the skull provides the fulcrum. Fins are responsible for controlling the pitch, yaw and rolling. Muscles are positioned in such a way that they facilitate complex movements required to initiate thrust. The fishes have a streamlined body that assists in the reduction of friction and drag. the method and pattern of movement, however, differs between species. Some of the most effective movements are observed in the anadromous salmonids, in the North American rivers. The fish migrate from the shallow streams as young fish and then shift back to the deep streams after maturing. The interpretation and significance of fish movement has been changing over time. Previously, researchers observed that most adult stream fishes limit their movements to a small area. These fishes do not move to areas beyond their home pool. Currently, researchers have differed with this observation and have instead concluded that fishes are not restricted in regard to their movement.