Date of Award

8-2015

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Biological Sciences

Advisor

Blob, Richard W

Committee Member

Blob, Richard W

Committee Member

Schoenfuss, Heiko L

Committee Member

Childress, Michael J

Committee Member

Sears, Michael W

Abstract

The ability of fish to escape from predators is a critical behavior for their survival. Experimental measurements of escape performance in fishes have typically been based on trials conducted in still water; however, such environmental conditions are rare in nature due to waves and currents that expose fishes to unsteady and/or directional flow. I examined the effects of water flow and predator attack direction on the escape behavior of fish, using juveniles of the amphidromous Hawaiian goby Sicyopterus stimpsoni as a model system. In nature, these fish must escape ambush predation by the Hawaiian sleeper, Eleotris sandwicensis, while exposed to rapidly flowing water. I measured the escape performance of juvenile gobies while exposing them to a range water velocities encountered in natural streams (0 cm/s, 15 cm/s, and 30 cm/s), stimulating fish with water jets from three different directions (front, side, and rear) to simulate the bow wave of an approaching predator. For trials in which stimulation elicited an escape response, there were limited effects of either flow speed or attack direction on escape trajectory, velocity, or acceleration. However, comparisons of response failure across treatments showed a strong effect of flow conditions on escape responses: whereas juvenile S. stimpsoni had uniformly high response rates for attacks from behind, rates of response for attacks from the front decreased dramatically as flow speed increased, up to 70% failure at 30 cm/s. Bow waves from predators attacking from the front might masked by the flow environment, impairing their potential to be detected by the lateral line systems of prey. Thus, the likelihood of successful functional performance in fishes can depend critically on environmental context, suggesting that changing environmental conditions might bear significantly on the outcomes of predator-prey interactions.

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Biology Commons

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