Personality, predation and group size: unravelling behavioural drivers of lionfish (Pterois volitans) invasion success

Global biodiversity is in rapid decline, with invasive alien species playing a major role. Predicting which is most damaging and under what conditions is key to proactive management. We investigated whether behavioural traits, specifically boldness and exploration, predict ecological impact in the invasive red lionfish (Pterois volitans). Despite the modest sample size of adults (n = 8) and juvenile (n = 8) lionfish, using repeated behavioural assays, we found strong personality consistency: 93% of juveniles and 56% of adults used shelter, with traits like latency to interact with novel objects showing high repeatability. Bold individuals spent less time in shelter and interacted more with novel stimuli. However, in groups of eight, personality expression shifted, with only 7% of juveniles and 44% of adults using shelter, indicating that social context alters behaviour. Functional response experiments revealed Type II feeding curves across three prey species, reflecting a saturating, hyperbolic relationship in which predators rapidly consume prey at low densities but are increasingly constrained by handling time as prey density rises. Neither adult nor juvenile lionfish reduced feeding effort when prey became scarce, allowing them to exert strong predation pressure even at low prey densities. Adults displayed significantly higher attack rates and shorter handling times on Artemia salina, whereas juveniles showed these patterns towards Gammarus oceanicus, underscoring the greater per capita feeding impact of adults. Contrary to expectations, boldness did not correlate with feeding impact but was linked to slower reaction times in shy individuals. These findings highlight the complex, context-dependent relationship between personality and ecological impact during invasions.