Meeting Abstract
Larval fishes experience extreme mortality rates, with 99% of a cohort perishing within days after starting to actively feed. The survival of these larvae is strongly dependent on their ability to capture prey. Most larval fish capture prey by rapidly expanding their mouth cavity, generating a “suction flow” that draws the prey into their mouth. Unlike adult fishes, larvae live in a hydrodynamic environment characterized by low Reynolds numbers (Re), which impedes their ability to capture prey. Experiments with non-escaping prey (Rotifers) shows the larvae have to execute high-effort strikes in order to “escape” the low Re regime and feed successfully, and that this ability is facilitated by ontogenetic growth. However, how these results extend to the larvae’s ability to feed on natural prey that does escape (e.g. copepods and copepodites) in response to hydrodynamic cues is unclear. We filmed Sparus aurata larvae (9-28 days post hatching) feeding on natural prey assemblages using 3D high-speed, high resolution camera system. This system enabled 3D tracking of landmarks on the prey and predator and calculation of their body movements and mouth kinematics. We observed four types of interactions where: (1) prey successfully escaped before the larvae opened its mouth, (2) prey successfully escaped after the larvae opened its mouth (3) prey was captured despite trying to escape, and (4) prey was captured without trying to escape. We used discriminant function analysis to understand which predator/prey kinematics best classified the interaction type, and discuss the results with respect to larval ontogeny.
