Swimming in an Unsteady World

Abstract
 
Studies on fish swimming have focused on time-independent motions in steady flows, while motions of fishes and the flows themselves are naturally unsteady. Unsteadiness in natural flows reflects the presence of vorticity, within which the range of structures and the predictability of flow seen by a fish are scale-dependent. Previous laboratory studies have described apparently contradictory results of unsteady flow on various behaviors. However, the confusion can be resolved when scale is taken into account. Unsteadiness in high Reynolds numbers flows in streams and on shorelines affect the distribution of fishes attributed to turbulence as a major source of perturbation that may challenge or overwhelm control systems. In a stream, characterized by highly unsteady flow, trout rest in habitats where flow is less unsteady. During storms on a wave-exposed shoreline, deep-bodied fishes tend to retreat to deeper water while fusiform species remain in more exposed habitats. Responses of fishes to unsteady flow are related to body/fin form. Overall, fish abilities to control stability in turbulence is a factor contributing to the organization of fish assemblages and such stability control should be incorporated into plans for biomimetic autonomous underwater vehicles.
 
Biography
 
Dr. Paul W. Webb is a Professor in the School of Natural Resources and Environment, and the Associate Director of the Program in the Environment at University of Michigan. He also holds a joint appointment with the Department of Ecology and Evolutionary Biology. Dr. Webb received his BS and PhD degrees in zoology from the University of Bristol, England, in 1967 and 1971, respectively. He is a member of a number of scientific and professional organizations, and was elected fellow of American Association for the Advancement of Science in 1983. He was also a founder member of the editorial board of Canadian Journal of Fisheries and Aquatic Sciences and the Journal of Experimental Biology. He is currently on the editorial boards of Journal of Fish Physiology and Biochemistry, and Marine Biology. His primary research is on biomechanics of fish swimming as an analytic approach towards understanding functional morphology, behavior, and ecology. The current focus is on stability and maneuverability of fishes in turbulent and still water habitats, and energy dissipation in thrust-related wakes. Field studies are seeking to apply biomechanical principles to shoreline management practices and restoration.
 
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