Turbulent flow reduces oxygen consumption in the labriform swimming shiner perch,Cymatogaster aggregata

Abstract

Fish swimming energetics are often measured in laboratory environments which attempt to minimize turbulence, though turbulent flows are common in the natural environment. To test whether the swimming energetics and kinematics of shiner perch, (a labriform swimmer), were affected by turbulence, two flow conditions were constructed in a swim-tunnel respirometer. A low-turbulence flow was created using a common swim-tunnel respirometry setup with a flow straightener and fine-mesh grid to minimize velocity fluctuations. A high-turbulence flow condition was created by allowing large velocity fluctuations to persist without a flow straightener or fine grid. The two conditions were tested with particle image velocimetry to confirm significantly different turbulence properties throughout a range of mean flow speeds. Oxygen consumption rate of the swimming fish increased with swimming speed and pectoral fin beat frequency in both flow conditions. Higher turbulence also caused a greater positional variability in swimming individuals (versus low-turbulence flow) at medium and high speeds. Surprisingly, fish used less oxygen in high-turbulence compared with low-turbulence flow at medium and high swimming speeds. Simultaneous measurements of swimming kinematics indicated that these reductions in oxygen consumption could not be explained by specific known flow-adaptive behaviours such as Kármán gaiting or entraining. Therefore, fish in high-turbulence flow may take advantage of the high variability in turbulent energy through time. These results suggest that swimming behaviour and energetics measured in the lab in straightened flow, typical of standard swimming respirometers, might differ from that of more turbulent, semi-natural flow conditions.

Thriving artificial underwater drag-reduction materials inspired from aquatic animals: progresses and challenges

“…The explanation for this is that it is not easy to think of uid adaptation (Kármán gaiting) as a specic behavior in aquatic animals motion but rather to harness high turbulence energy that changes with time. 8 The streamlined body optimizes the pressure gradient of the entire body so that the uid body squeezes the back, abdomen, or side of the aquatic animals to a minimum, and also reduces the effect of differential pressure drag when swimming at high speed. 11 The streamline has a rounded front and pointed rear, smooth surface, and slightly droplet shape; thus, good pressure gradient and laminar ow in water are regarded as the characteristics of a streamlined structure.…”

“…These motion patterns can reduce the follower's energy consumption by 30% and improve the swimming efficiency by 20%. 113 The oxygen consumption of the fish during exercise was measured by; 8 it was a surprise to find that fish consume less oxygen at high turbulence than at low turbulence at medium and high swimming speeds. The explanation for this is that it is not easy to think of fluid adaptation (Kármán gaiting) as a specific behavior in aquatic animals motion but rather to harness high turbulence energy that changes with time.…”

“…Also, the energy consumption of sh organisms in water is different from common sense. 8 During the active motion of aquatic animals, they accelerate intermittently, then constantly maintain the cruise speed, and alternately climb and sink forward. 9,10 Moreover, biological aquatic animals are "stingy" with their energy while adapting to underwater activities and their cruising strategy is to spend the least energy to reach the maximum distance of sailing from an evolutionary perspective.…”

“…11 In the experiment, aquatic animals utilized less oxygen in highturbulence compared with low-turbulence ow at medium and high swimming speeds, i.e., energy consumption is weakened. 8 Aquatic animals not only utilize the turbulent ow state but also borrow the disturbance generated by other large moving objects, which changes their body motion by staying behind the hull and 'synchronize' with the current vortex, thereby reducing energy consumption. This behavior is called Karman gaiting.…”

Effects of wave-driven water flow on the fast-start escape response of juvenile coral reef damselfishes

“…These complex flows can be energetically demanding (e.g. Roche et al, 2014;Maia et al, 2015;Schakmann et al, 2020) or beneficial (Taguchi and Liao, 2011;van der Hoop et al, 2018) for fishes, and can have destabilizing effects on important behaviours, including those associated with predator-prey interactions (Webb, 2002;Webb et al, 2010). Currently, the extent to which wave-driven water flow affects fish escape responses is unknown.…”