Reef fishes innately distinguish predators based on olfactory cues associated with recent prey items rather than individual species

An individual’s ability to identify and respond accurately to a predator greatly affects its probability of survival. Chemosensory cues are an important mechanism for predator detection in aquatic environments. Whether fish are aware of the risks posed by distinct fish species, or whether a common chemosensory cue distinguishes predatory fishes, is unknown. One possibility is that fish distinguish predatory fishes based on their diet. To test this, we manipulated the diet of three nominally nonpiscivorous species and examined behavioural responses of juvenile anemonefish, Amphiprion percula, to chemical cues of nonpredators fed a diet rich in fish product. In pairwise choice trials, naïve A. percula showed indifference to chemosensory cues from nonpiscivorous fishes fed their usual diet, but significantly avoided chemical cues from piscivorous and nonpiscivorous fishes fed a diet containing fish product. These results indicate that A. percula larvae innately distinguish between piscivorous and nonpiscivorous fishes based on chemosensory cues in the diet. To test for an effect of piscivorous diet in nature, we constructed patch reefs that emitted scents of dietary cues in natural concentrations. Patches that emitted scent of a piscivorous diet received on average 22% less settlement than control patches or than patches that emitted scent of an herbivore or invertivore. Chemosensory detection of recent prey provides a robust cue to assess predation risk associated with a diverse range of fishes (especially during settlement) and may be reinforced through additional sensory (e.g. visual) and learned recognition of individual species consistently associated with these distinctive chemosensory cues.

► Olfactory cues are used for innate predator recognition in coral reef fish.
► Dietary components may be used for recognition.
► Nonpredators were identified as predators when fed a fish-based diet.
► Larval fish identify risk through generalized olfactory cues in the diet of piscivores.