Response to visual and mechano-acoustic predator cues is robust to ocean warming and acidification and is highly variable in European sea bass

Abstract

Predator-prey interactions and, especially, the success of anti-predator responses are modulated by the sensory channels of vision, olfaction, audition and mechanosensation. If climate change alters fish sensory ability to avoid predation, community dynamics can be affected. We investigated whether mid-duration exposure to warming and/or acidification alters behavioural response to visual or mechano-acoustic predator cues in juvenile Dicentrarchus labrax. We measured kinematic variables before and after a visual or a mechano-acoustic challenge which mimicked an overflying bird shadow or a bird swoop attack, respectively. Due to large interindividual variability in responses before cue presentation, fish were categorized as slow and fast to account for baseline individual variability. Treatment did not impact kinematic variables as both slow and fast fish of every treatment elicited precautionary and escape responses. Interestingly, even slow fish swam as fast as fast fish after the cue, suggesting that regardless of initial category, fish managed to escape facing a danger. Anti-predator response varied according to the level of threat to survival with greater responses elicited after the swoop attack. Although wild juvenile sea bass aggregate in schools, school dynamics rely on single leaders which highlights the importance of the variability in individual behaviours. We demonstrated that anti-predator response in juvenile D. labrax is robust to mid-duration exposure to independent and combined effects of warming and acidification. If robustness is confirmed over long-duration, it could provide D. labrax with an evolutionary advantage in the future ocean, where cue transmission through changing environments can further modulate cue perception and predator-prey interactions.