Session MD - Bio-Fluid Dynamics X.
MIXED session, Tuesday afternoon, November 23
Fifth Avenue Room, Westin Seattle
Among many ecologically important aspects of locomotion, turbulence is thought to create large stability challenges for fishes. Turbulence is a ubiquitous, highly variable feature of aquatic habitats. Species that are more prevalent in energetic water (high flow, high turbulence) have more effective control systems and greater ability to generate propulsive power to maneuver. Fishes experience a wide range of velocity variation and vorticity in their natural habitats. Current research shows that response times to disturbances are sufficiently long that powered corrections of resulting disturbances risk ``pilot-induced error.'' Therefore, the ability to stabilize posture and trajectories should be important in habitat choice. Preliminary observations in a trout stream with an Acoustic Doppler Velocimetry (ADV) are presented. The measurements are used to determine flow signatures in various habitats occupied and vacant of fishes. A significant difference in turbulence intensity and average velocity for sites occupied by large fishes versus small fishes is found. Furthermore, a comparison between occupied sites and typical flow conditions encountered in the stream is performed.