Meeting Abstract

91.1  Monday, Jan. 6 13:30  Hydrodynamic starvation in first-feeding larval fishes HOLZMAN, RH*; CHINA, V; ZILKA, M; YANIV, S; ELAD, D; Tel Aviv University; Tel Aviv University; Tel Aviv University; Tel Aviv University; Tel Aviv University holzman@post.tau.ac.il

Larval fishes suffer prodigious mortality rates, typically eliminating 99% of the brood within a few days after first feeding. Hjort (1914) attributed this “critical period” of low survival to the larvae’s inability to obtain sufficient food. Larvae feed by generating suction flows that carry the prey into their mouth. This feeding mechanism is conserved across life stages, despite a dramatic transition of larvae from a viscosity-dominated low Reynolds at first feeding to an inertia-dominated high Reynolds regime at larger sizes. Using numerical simulations, hi-speed filming, and feeding experiments we examine suction performance in larval fishes. Our data shows that hydrodynamic constraints on the suction mechanism in first-feeding larvae strongly affect larval feeding rates. We manipulated water viscosities to quantify age-independent effects of the hydrodynamic regime on feeding performance. These dynamic-scaling experiments revealed that larvae size is the primary determinant of feeding rates, independent of other ontogenetic effects. We conclude that first-feeding larvae experience “hydrodynamic starvation” in which low Reynolds numbers mechanistically limit their feeding potential. Thus, starvation of first-feeding larvae may occur even under apparent high densities of high-quality food, providing a likely mechanism for Hjort’s “Critical Period”.