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

Shoaling in fishes is regulated by factors like predation, vegetation cover, water flow and food availability. Shoals detect and respond to changes in these ecological factors using a multimodal sensory system. Here, we examine the immediate response of wild-caught zebrafish ( Danio rerio) shoals to cues from its natural predator, the snakehead ( Channa sp .). Zebrafish shoals were recorded upon exposure to (1) olfactory predator cues, (2) visual predator cues, (3) both cues together, and (4) no cue. We tracked individuals and analysed shoal responses across these treatments. We found that compared to control treatments, shoals receiving either visual or olfactory cues had significantly greater: (i) cohesion, (ii) polarization and (iii) velocity. Interestingly, when the shoals received both cues simultaneously, the cohesion, polarization and velocity decreased and a significantly greater number of individual freezing events occurred. Therefore, zebrafish relied on both visual and olfactory cues to escape predation. However, when shoals were presented with both cues together, while freezing frequency increased, other responses were comparable to control treatments where no predator cue was provided. While this study indicates that multimodal cues elicit a different anti-predator response than the cues singly, more experiments are required to identify the underlying cause of this behaviour.