Meeting Abstract
Calanoid copepods are prime prey of fish larvae, however, often the prey succeeds in escaping from the approaching predator owing to their exquisite detection and evasion capabilities. Using the sub-tropical copepod, Bestiolina similis as a model prey, we conducted experiments to assess the capability of adult and copepodid stages to detect and escape from a stealthy predator, the larval clownfish Amphiprion ocellaris. The sensitivity of the copepod to an approaching fish was determined using a hydrodynamic model to estimate the rate of water deformation around the copepod as a function of the measured distance to the approaching fish, the fish size, its location, and its velocity. The model was validated by tracking the movement of tracer particles in the bow wave of a swimming fish. We then analyzed the responses of prey to the approach and pre-strike tactics of planktonic-phase clownfish. Escape-directions and -speeds of copepods that successfully detected the predator before its strike were recorded and analyzed. The majority of escapes from such an approach were oriented away (120° to 180° with respect to an approach of 0°), with a few escapes oriented toward but to the side of the fish (0° to 60°). The fewest escapes were directed perpendicular to the approaching fish. Key features of the hydrodynamic disturbance that elicited successful escapes from the approach were identified for both copepodite and adult copepod stages to determine whether there were any differences in sensitivity or escape-direction between these two developmental stages.
