Hydrodynamic Constraints of Suction Feeding in Low Reynolds Numbers, and the Critical Period of Larval Fishes

Abstract

Larval fishes suffer prodigious mortality rates, eliminating 99% of the cohort within a few days after their first feeding. Hjort (1914) famously attributed this "critical period" of low survival to larval inability to obtain sufficient food. We discuss recent experimental and modeling work, suggesting that the viscous hydrodynamic regime have marked effects on the mechanism of suction feeding in larval fish. As larvae grow, the size of the gape and associated volume of the mouth increase. At the same time, larvae swim faster and can generate faster suction flows, thus transiting to a hydrodynamic regime of higher Reynolds numbers. This hydrodynamic regime further leads to changes in the spatio-temporal patterns of flow in front of the mouth, and an increasing ability in larger larvae to exert suction forces on the prey. Simultaneously, the increase in swimming speed and the distance from which the prey is attacked result in higher rates of encountering prey by larger (older) larvae. In contrast, during the first few days after feeding commence the lower rates of encounter and success in feeding translate to low feeding rates. We conclude that young larvae experience "hydrodynamic starvation," in which low Reynolds numbers mechanically limit their feeding performance even under high densities of prey.

Pulsing corals: A story of scale and mixing

“…the cardiovascular system) [6], flows generated for filtering [7], and flows for photosynthetic enhancement [8]. As is the case for locomotion, different pumping and feeding mechanisms may only be effective over some range of Re f [9], [10]. In this paper, we quantify the flows produced by a variety of soft corals, including the genera Xenia and Heteroxenia, that actively pulse and contribute substantially to local ocean mixing, enhancing nutrient availability in reefs.…”

Characterization of zebrafish larvae suction feeding flow using μPIV and optical coherence tomography

“…Somewhat surprisingly, larval mortality is also extremely high in mariculture facilities, where food is abundant and conditions are stable. It has recently been suggested that this mortality could be attributed to the hydrodynamic regime in which larvae dwell (China and Holzman 2014;Holzman et al 2015;Yaniv et al 2014). Like most aquatic vertebrates, larval fish exploit a physical reality by suction feeding to exert a hydrodynamic force on their prey.…”

“…The spatiotemporal properties of the fluid flow generated due to this buccal expansion determine the efficiency of food intake Yaniv et al 2014) and the efficiency detrimental for the survival of fish larvae (Parra and Yúfera 2000). While much is known about these patterns in juvenile and adult fishes, no direct measurements are yet available for fish larvae (reviewed in Day et al 2015;Holzman et al 2015).…”

Automated detection of feeding strikes by larval fish using continuous high-speed digital video: a novel method to extract quantitative data from fast, sparse kinematic events

“…A low feeding rate (especially in the first days posthatching) results in a scarcity of feeding attempts in the visualized area . Similar to adults, prey capture in larvae takes a few tenths of a millisecond (China and Holzman, 2014;Hernandez, 2000;Holzman et al, 2015), easily missed by the naked eye or conventional video.…”

“…Recently, continuous high-speed photography of long sequences (∼100,000 frames) has shown that the prey capture success rates of early-stage larvae are substantially lower than those of their older counterparts (China and Holzman, 2014;Holzman et al, 2015).…”