Meeting Abstract
Fish swim in complex hydrodynamic environments and probably rely on multiple sensory modalities for stabilizing swimming in unsteady flows. It is unclear how the lateral line system and vision contribute to a fish’s ability to compensate for different types of unsteady flows, including horizontal vortices (like those shed by waterfalls in a stream). Here we tested the relative importance of the lateral line system and vision in bluegill sunfish (Lepomis macrochirus) swimming in horizontal vortices generated by a custom-made flapper. To examine the importance of vision, swimming behavior was filmed under infrared light, and to examine the importance of the lateral line, fish were treated with cobalt chloride to temporarily deactivate the lateral line system. During each trial, a fish was positioned behind the flapper (frequency = 0.5 Hz) while swimming at 0.28 body lengths/s and recorded with two high-speed cameras to obtain the center of mass velocity, the fish’s relative distance and elevation to the flapper, any changes in orientation, and movement of its caudal fins relative to the flapper’s movement. Interestingly, few differences from the control were observed when vision, or the lateral line system, or both were disabled. Fish swam closer to the flapper when their lateral line systems were inactivated, but they did not change their velocities, elevation, or orientation towards the flapper. Caudal fin movements also did not change significantly during the different trials. Therefore, passive properties of the fish’s body likely played a greater role in maintaining stability while swimming in horizontal vortices than sensory input from the lateral line and visual systems.
