Use of multimodal sensory cues in predator avoidance by wild-caught zebrafish shoals

Abstract

Abstract Fishes rely on a multimodal sensory system to assess cues from environmental factors, such as predation, vegetation cover, water flow and food availability. Here, we conducted laboratory-based experiments to examine the immediate response of wild-caught zebrafish (Danio rerio) shoals, comprising ten individuals, to one of the following treatments: (1) olfactory predator cue; (2) visual predator cue; (3) both cues simultaneously; and (4) control with no cue. Experiments were performed in a 75cm × 75cm arena, and test shoals were provided with olfactory cues from a predator and with a model predator as visual information on the presence of a predator. Using the idTracker software, we tracked and analysed shoal responses across these treatments. We found that in comparison to the control treatment, shoals receiving either visual or olfactory cues had significantly greater: (1) cohesion (inter-individual distance); (2) polarization (tendency of shoal members to orient in a common direction); and (3) velocity (directional speed). Interestingly, when the shoals received both visual and olfactory cues simultaneously, the cohesion, polarization and velocity decreased, and such shoals exhibited significantly more individual freezing events. Therefore, our study not only indicates that zebrafish rely comparably on vision and olfaction to escape predation but also shows that the anti-predator response elicited by zebrafish varies based on the number of cues provided.