3-D motion and deformation of pectoral fins of a goby in maneuvering swims

Abstract

Motions and deformations of the flapping pectoral fins of a goby (Tridentiger obscurus) in maneuvering swims were three-dimensionally analyzed. Fluorescent markers were attached to the fins and body for video recording. The fish showed four types of maneuvers: hovering, ascending, turn, and backward swimming. It was found that the time difference between the left and right pectoral fin strokes varied widely from in-phase to out-of-phase depending on the maneuvers. The flapping angle varied as much as 150°, and the area of the pectoral fin was reduced to 33% of its maximum value. Furthermore, unlike previously known pectoral-fin-propelled fishes, the leading edge of the pectoral fin demonstrated notable bending deformation up to 41°. In addition, in backward swimming, the trailing edge of the pectoral fin preceded the leading edge unlike the other general fish of which leading edge precedes the trailing edge.