Effect of early exposure to predation on risk perception and survival of fish exposed to a non-native predator

Abstract

Exposure to predation should affect prey responses to predators by selecting for threat recognition and/or general risk avoidance. We investigated whether native and non-native predator density on the home reefs of juvenile striped parrotfish, Scarus iseri, which reflects their early exposure to predation risk, influences their behavioural responses and survival when faced with some of these predators under controlled conditions. In aquaria, parrotfish exhibited evasive behaviour, in the form of increased immobility and increased distance from threat, in response to visual and chemical cues from native predatory grouper (Epinephelus striatus) but not from invasive Indo-Pacific lionfish (Pterois sp.), suggesting no evidence of risk perception in relation to the non-native predator. However, parrotfish from high-risk reefs exhibited more evasive behaviours and colour responses (i.e. more mottled coloration) in response to all stimuli than parrotfish from low-risk reefs. Moreover, more parrotfish from high-risk reefs than from low-risk reefs survived in direct encounters with lionfish, and those parrotfish that survived were those that had displayed increased immobility when exposed to lionfish cues. We suggest that predation, especially by non-native lionfish, targeting risk-taking fish could result in greater overall cautiousness in some prey populations. This heightened risk avoidance ultimately aids prey fish to evade non-native lionfish, even in the absence of predator recognition.