Meeting Abstract
Studies have typically evaluated the escape responses of fishes in still water; however, such environmental conditions are rare in nature due to waves and currents exposing fishes to unsteady and/or directional flow. We examined the effects of water flow on the escape behavior of fish, using juveniles of the amphidromous Hawaiian gobiid Sicyopterus stimpsoni as a model. After metamorphosis from marine larvae, juvenile S. stimpsoni enter fresh water streams and, as they commence migration to adult habitats, they must avoid a sit-and-wait predator, the sleeper Eleotris sandwicensis. Thus, in nature, these fish must escape predation while exposed to rapidly flowing water. We used high-speed video (1000 Hz) to measure the escape trajectories of juvenile gobies while exposing them to different water velocities encountered in natural streams (0, 15, and 30 cm/s), using a custom-built flow tank. Trials were conducted with stimuli (water jets) imposed from three different directions (front, side, and rear). MANOVA results indicate significant differences in escape trajectories among the different flow speeds and attack directions. High flow speeds showed the greatest percentage of trials in which stimuli failed to elicit an escape response. However, when responses were elicited, escape angles were greater when fish were attacked from the front than from other directions. Given the presence of varying flow conditions in aquatic habitats, this environmental context is relevant to the escape responses of many fish species.
