Collective response of fish to combined manipulations of illumination and flow

Stability of schooling patterns of a fish pair swimming against a flow

“…There is a critical interfish distance at which the pair transition from a stable staggered to a stable in-line state; this critical distance decreases with flow curvature. These two configurations (in-line and side-by-side) have also been found in experiments with live fish (Ashraf et al., 2017; De Bie et al., 2020; Lombana & Porfiri, 2022). In particular, experiments in the dark conducted by Lombana and Porfiri (2022) have demonstrated that fish can swim in either of these two configurations, without the need to appraise their relative position in the pair through vision.…”

“…These two configurations (in-line and side-by-side) have also been found in experiments with live fish (Ashraf et al., 2017; De Bie et al., 2020; Lombana & Porfiri, 2022). In particular, experiments in the dark conducted by Lombana and Porfiri (2022) have demonstrated that fish can swim in either of these two configurations, without the need to appraise their relative position in the pair through vision. Our analysis further shows that the system has no stable configuration (except wall-perpendicular) if the fish are extremely close in streamwise direction, thus rendering a precisely side-by-side upstream swimming formation unstable.…”

“…Therefore, for a given value of , the corresponding channel width measured in terms of fish body length is . In this study, we vary such that the corresponding channel width is two to four times the body length, as commonly used in experiments (Liao, Beal, Lauder, & Triantafyllou, 2003b; Lombana & Porfiri, 2022), as well as the case of no channel walls ( or ). The literature in modelling the lateral-line sensing mechanism to support rheotaxis is relatively scarce and only a few recent works (Burbano-L & Porfiri, 2021; Porfiri et al., 2022) use non-dimensional lateral-line feedback.…”

“…Table 1. Ranges of model parameters 𝛼, 𝜌 and 𝜅 and other important parameters considered in this work based on Oteiza et al (2017), Coombs et al (2020), Liao et al (2003b), Burbano-L and Porfiri (2021), Porfiri et al (2022) and Lombana and Porfiri (2022).…”

“…Recent work by De Bie, Manes, and Kemp (2020) has further shown that pairs of fish tend to swim in-line in placid water, side-by-side in a high speed flow, and without any identifiable pattern in a low-speed flow. Examining the combined effect of flow (hydrodynamic interaction) and illumination (visual interaction) on fish collective behaviour, Lombana and Porfiri (2022) provided evidence that the relative time spent by a pair in a side-by-side configuration increases in the presence of flow as well as in the presence of light. However, in these studies the different forms of interactions (visual, hydrodynamic and tactile) are intermingled, and the specific role of hydrodynamics is difficult to tease out.…”