Biomechanics and Evolution of Fish Locomotion

A major research focus of my laboratory is the locomotor biology of fishes that generate forward propulsion by oscillating and undulating the fins. We ask the questions: How are fishes designed to swim efficiently and with such high maneuverability? How are the muscle-tendon-bone systems that provide thrust coordinated by neuromotor control? How has locomotion evolved in complex 3-dimensional coral reef environments? Techniques used in locomotor biomechanics include kinematics, electromyography, sonomicrometery, and modeling of the biomechanics and hydrodynamics of locomotion. We study three-dimensional kinematics of fin motions by using high-speed videography. To understand the role of muscles in fish swimming behaviors, we use electromyography to record the activity patterns of major muscles. Sonomicrometry provides direct estimates of muscle shortening in living fishes. Finally, we construct biomechanical models of locomotor systems that provide a rigorous basis for comparison among species.

Fin locomotion in the Labridae. Labrid fishes fly underwater as they soar around the complex reef structures on which they live. Labrids are incredibly diverse in size, body shape, and locomotor mechanisms, but they share a reliance on the pectoral fins (their "wings") to provide thrust for swimming. What are the structural and functional features that determine locomotor behavior and performance in labrids? I have established an integrative research program on the swimming mechanics of labrid fishes, including studies of kinematics (Walker and Westneat, 1997), electromyography (Westneat and Walker, 1997), swimming performance (critical swimming speed), and phylogenetic trends in locomotor biology (Westneat, 1996). Research on the hydrodynamics of fin propulsion has been advanced through blade-element modeling of the fin stroke (Walker and Westneat, 2000).