Behavioural responses to simulated bird attacks in marine three-spined sticklebacks after exposure to high CO2 levels

Abstract

The rising partial pressure of CO2 (pCO2) in oceanic water, termed ocean acidification, is an impending threat to marine life and has previously been reported to affect several aspects of fish behaviour. We evaluated the behavioural response to a simulated avian predator attack and lateralisation in three-spined sticklebacks (Gasterosteus aculeatus) after 10 and 20 days of exposure to present day pCO2 (400μatm) or elevated pCO2 (1000μatm). We show that elevated pCO2 lead to reduced behavioural lateralisation. However, no major differences in the sheltering response after an overhead avian attack were observed; fish from both treatments exhibited similar and strong responses. Compared with fish exposed to high pCO2, the control fish took longer time to freeze (i.e. stop moving) after attack at Day 20 but not Day 10. The freezing duration was significantly reduced between Day 10 and Day 20 in elevated pCO2, whereas no such reduction was observed in the control-group. However, no significant differences between treatment groups were detected at Day 20. These results demonstrate that behaviour is indeed altered by high CO2 levels, although the general responses to avian predation stimuli remain similar to those of unexposed fish, indicating that some predator avoidance behaviours of three-spined sticklebacks are robust to environmental disturbance.