“…Mixed-species shoaling behaviour has been described across a range of aquatic systems (Appendix S1), in some cases being as common or more common than single-species shoaling (e.g. temperate lake fishes [Krause, Godin, & Brown, 1998], and small pelagic fishes [Louw, Fréon, Huse, Lipiński, & Coetzee, 2014]), however, inherently contradicts the view that similarity in phenotype, behaviour and physiology among shoal members is a central contributor to fitness. Unsurprisingly, the body of research from which our understanding of shoaling behaviour is derived has historically centred on singlespecies shoals (Breder, 1959;Pitcher, 1993;Shaw, 1978;Sridhar & Guttal, 2018), with a relatively small number of publications invested in understanding the significance of mixed-species shoaling ( Figure 1).…”