Temperature and food availability affect risk assessment in an ectotherm

• We examined effects of food availability and temperature on risk assessment in fish.
• Hungry fish at higher temperature take greater risks under predation threat.
• Risk-prone behaviour is likely in order to satisfy energetic requirements.

Risk assessment in ectotherms is strongly affected by an organism's energy expenditure and acquisition because these will alter the motivation to feed, which is balanced against antipredator behaviours. Temperature and food availability are known to affect the physiological condition of ectotherms, but how interactions between these variables may influence predator–prey dynamics is still poorly understood. This study examined the interactive effects of food availability and temperature on the trade-offs between predator avoidance behaviour and foraging in juveniles of a marine damselfish, Pomacentrus chrysurus. Predator avoidance behaviour was tested by exposing fish to chemical alarm cues obtained from skin extract of conspecifics. When detected, these cues elicit an antipredator response in fish, typically characterized by decreased foraging. Fish maintained under high food ration displayed distinct antipredator responses to chemical alarm cues, regardless of temperature. However, fish maintained in conditions of low food ration and 3 °C above ambient temperature did not display an antipredator response when exposed to chemical alarm cues, whereas those in ambient temperature did. These results suggest that individuals in low physiological condition because of limited food availability are more susceptible to increased temperature and may therefore take greater risks under predation threats to satisfy their energetic requirements.