Meeting Abstract
58.3 Thursday, Jan. 6 Velocity-dependant energetics hierarchy for trout swimming in vortical flows LIAO, James C.*; TAGUCHI, Masashige; Whitney Lab, U. Florida Gainesville jliao@whitney.ufl.edu
Measuring oxygen consumption (MO2) provides a direct and non-invasive way to assess the energetic cost of swimming. We use intermittent flow respirometry to show that there are multiple regions around a cylinder in flow that rainbow trout (Oncorhynchus mykiss) will hold station. We show that an energetics hierarchy, by which different station holding behaviors around a cylinder require different MO2 values, exists even at a fixed flow velocity. At 3.5 body lengths per second (L s -1 ), entraining shows the lowest MO2 (115.4 ± 4.0 mgO2/kg/hr), followed by Kármán gaiting (136.8 ± 4.0 mgO2/kg/hr), bow waking (188.0 ± 4.0 mgO2/kg/hr), and then free stream swimming (289.8 ± 4.3 mgO2/kg/hr). As flow speed increases, these costs change in complex ways. At times, MO2 actually decreases with increasing flow velocity. Entraining demands the least energy at 3.5 L s -1 , while bow waking requires the least energy at 5.0 L s -1 . Differences in MO2 trends reveal that certain behaviors at one speed have the same costs as other behaviors at another speed (e.g. bow waking at 5.0 L s -1 requires the same amount of oxygen as entraining at 3.5 L s -1 ). We directly show that Kármán gaiting fish gain an energetic advantage from vortices beyond the benefit of swimming in a velocity deficit. Our experimental data on the complex patterns of swimming costs in turbulence cautions against extrapolating results from uniform flow studies to swimming performance in the field. All values are mean ± standard error, n= 3 fish.
