A New Metric for Characterizing Swimming Kinematics in Elongate Fishes

Many species of elongate fishes use Anguilliform swimming to propel themselves through the water (Gillis 1996, Long 1998). A fish using this method passes a wave of motion from the head, through the body, to the tail causing thrust. This type of swimming is the only one in which the entire body is used as opposed to just the caudal end such as in Thunniform swimmers (Tytell 2010). When watching certain species of elongate fishes swim, an interesting rotation in the body can be observed. If the fish is being looked at dorsally as it swims, there is a clear view of the lateral side of the fish as the tail beats back and forth. This view changes as the fish passes the wave from its head to its tail. The current work will describe a new method for measuring this rotation, or wobble, in the fish as it is swimming