What drives mixed-species shoaling among wild zebrafish? The roles of predators, food access, abundance of conspecifics and familiarity

Abstract

Mixed-species groups occur across a wide range of faunal communities and provide several benefits to members. While zebrafish have often been observed to form mixed-species shoals with coexisting species, the factors determining their occurrence are not yet fully understood. Shoals comprising zebrafish (Danio rerio), flying barbs (Esomus danricus), and whitespots (Aplocheilus panchax) were collected from a stagnant canal at Haringhata (West Bengal, India), and using laboratory-based experiments, we deciphered likely drivers of mixed-species shoaling among zebrafish. Experiments assessing foraging efficiency revealed that the amount of food consumed by zebrafish individuals in mixed shoals was comparable to the amount consumed by these individuals in conspecific shoals. Within mixed-species shoals, zebrafish individuals, despite being smaller than the other species, consumed a comparable amount of food as the other species. Shoal choice experiments revealed that under predator risk, zebrafish associate more with mixed shoals and showed comparable associations to shoals differing in the abundance of conspecifics. Furthermore, zebrafish preferred associating with familiar conspecifics over unfamiliar mixed and unfamiliar conspecific shoals. Therefore, equitable food consumption in mixed shoals, greater association with mixed shoals in the presence of predators, and familiarity were important in driving zebrafish towards mixed-species shoaling.

Swimming under Pressure: The Sub-Lethal Effects of a Pesticide on the Behaviour of Native and Non-Native Cypriniformes Fish

“…Boldness (i.e., the tendency to leave a refuge and explore an unknown exposed environment) is another significant behavioural trait observed in fish [35,36] and is linked to responses to stimuli [37,38], predator inspection in school leaders, and predator evasion [39,40], dispersion [41][42][43], and activity [44][45][46]. Shoaling cohesion and other social behaviours are known to affect the survival of fish living in groups [47,48] by improving threat perceptions [49,50] and reducing individual risks and physical costs of movement [51][52][53]. Aggregation has other benefits, such as improved foraging efficiency [54], predator encounter dilution, and predator confusion [55][56][57].…”